Difference between revisions of "Exploring Hydrological Analyses using ILWIS"
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==Purpose== |
==Purpose== |
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| + | [[File:ilwis_logo.png|frame|ILWIS Logo]] |
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| − | This Wiki tutorial has been produced for the purpose of exploring and describing the methods used for hydrological analyses in ILWIS (a FOSS4G program). The objective of this tutorial is to provide users with a better understanding of how the hydrological analyses within ILWIS works, in addition to providing the instructions necessary to reach the desired output for their study region. |
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| + | This Wiki tutorial has been produced for the purpose of exploring and describing the methods used for hydrological analyses in ILWIS (a FOSS4G program). The objective of this tutorial is to provide users with a better understanding of how the hydrological analyses within ILWIS works, in addition to providing the instructions necessary to reach the desired output for their study region. Additionally, this tutorial will allow for comparison of ILWIS and SAGA GIS, using the same data for analysis as the [http://gracilis.carleton.ca/CUOSGwiki/index.php/Exploring_Hydrological_Analyses_using_SAGA_GIS Exploring Hydrological Analyses using SAGA GIS] tutorial from 2013. |
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| + | This project will focus on hydrological analysis of Okanagan Lake, a popular tourist destination in British Columbia, Canada. The tutorial will cover topics such as filling sinks, flow direction, DEM visualization and drainage network mapping through the use of ILWIS hydrological analysis tools. |
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| − | ==Introduction== |
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| − | ILWIS stands for "Integrated Land and Water Information System". It is a open source Geographic Information System software program that was designed tobe a user-friendly integrated software that contains both raster and vector processing capabilities, allowing for both analyses on remotely sensed images, vector maps and numerous spatial modeling abilities. This tutorial will focus on its ability to use Digital Elevation Models (DEMs)to run hydrological analyses of a study region. |
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| + | ==Introduction to ILWIS== |
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| − | [[File:Ilwis Logo]] |
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| + | ILWIS stands for "Integrated Land and Water Information System". It is an open source Geographic Information System software program that was designed to be a user-friendly integrated software that contains both raster and vector processing capabilities, allowing for both analyses on remotely sensed images, vector maps and numerous spatial modeling abilities. ILWIS was developed by the International Institute for Aerospace Survey and Earth Sciences (ITC) in The Netherlands. This tutorial will focus on its ability to use Digital Elevation Models (DEMs) to run hydrological analyses of a study region. More information about this product can be found on the [https://52north.org/software/software-projects/ilwis/ ILWIS Website] |
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==Methods== |
==Methods== |
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| − | ===Spatial Multiple Criteria Evaluation=== |
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| + | ===Software Download and Installation=== |
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| − | Spatial Multiple Criteria Evaluation (SMCE) is a method that assists stakeholders in decision making with respect to achieving a particular goal. It is an ideal tool for transparent group decision making, using spatial criteria, which are combined and weighted in line with the overall goal. For implementing the analysis in this study, the SMCE module of ILWIS was used. The input are set of data that are spatial representation of the criteria (used as factors and constraints), which are standardized and weighted in a criteria tree. The theoretical background for the multi-criteria evaluation is based on the Analytical Hierarchical Process (AHP) developed by Saaty (1980). |
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| + | ILWIS 3.8.5 can be downloaded for free from the [https://github.com/52North/Ilwis3Downloads GitHub page for 52 North]. This is the most recent version of ILWIS 3 and was released on September 3, 2015. Since the release of this version, the ITC has released ILWIS 4. It is likely that new versions of ILWIS 3 will eventually stop being released, as the capabilities of ILWIS 4 become greater. More information about ILWIS 4 can be found on the [http://ilwis.itc.utwente.nl/wiki/index.php/Main_Page ILWIS 4] website. |
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| + | ===Data Sourcing=== |
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| − | Generalized procedure for conducting SMCE is shown below: |
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| + | In order to carry out this exercise, a DEM of the area of interest is needed. For this project an open data DEM was obtained using the [http://maps.canada.ca/czs/index-en.html Geospatial Data Extraction Tool] created by Natural Resources Canada. |
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| + | Digital Elevation Models for locations outside of Canada can be obtained using the [http://earthexplorer.usgs.gov/ EarthExplorer Tool] created by the United States Geological Survey (USGS). |
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| − | [[Image:SMCE_Procedure.bmp|400px]] Figure 1:Generalized Procedure for conducting SMCE Analysis |
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| + | ===Starting ILWIS=== |
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| − | Source:EL YOUNQUE Ecosystem Services |
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| + | '''Before starting any analysis, create a working folder and ensure all data needed are in this folder. Keeping all your data in one folder makes analyses easier.''' |
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| + | ---- |
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| + | *Ensure that ILWIS 3.8.5 is properly installed on your computer |
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| + | *Locate ILWIS from the program list and double click on the icon to launch program |
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| + | *ILWIS main page will open |
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| + | *Use the ILWIS Navigator Tab to locate your working folder. The Navigator lists all drivers and directories. |
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| + | [[File:ILWIS_Interface2.png|800px]] |
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| − | ===Data=== |
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| + | ''Figure 1: Screenshot of ILWIS Interface'' |
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| − | In order to carry out this exercise, multiple datasets are needed to form the bases for setting criteria. These criteria will be the factors and constraints for selecting suitable landfill sites. |
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| − | For this project, existing vector data layers were acquired from this university's Maps, Data and Government Information Centre (MADGIC). For information on how to acquire these data contact MADGIC through this website:http://www.library.carleton.ca/library-news/category/MADGIC. Other suitable data can be found in your local map library or on the Internet. |
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| + | ===Importing a DEM=== |
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| − | For this task, the following datasets were used to form maps of Factors (phenomena that contribute variably to site suitability) and Constraints (phenomena that have binary impacts on suitability): |
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| + | Before any analysis can be completed, a DEM of the region of interest must be imported into ILWIS. |
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| + | :1) Click Operations --> Import/Export --> GDAL (Geospatial Data Abstraction Library) |
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| − | *Roads – gravel or paved (major roads) |
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| + | [[File:ImportDEM_1.png|800px]] |
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| − | *Waterbody- open water, rivers, lakes |
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| + | ''Figure 2 - Finding the import tool in ILWIS'' |
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| − | *Contour- elevation in meters |
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| − | *Sensitive Area- wetlands |
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| + | ::* An Import window will open |
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| − | *Builtup Area- residential, commercial (developed areas) |
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| + | [[File:ImportDEM_2.png|500px]] |
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| + | ''Figure 3 - ILWIS import window'' |
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| − | Factors |
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| − | 1) Proximity to major roads |
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| + | :2) Click to the DEM you want to import and ensure that the import format is set to Use GDAL. |
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| − | 2) Proximity to slope |
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| + | :3) Give your Output DEM a name and click OK. |
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| − | 3) Proximity to waterbody |
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| + | ::* The new DEM (compatible in ILWIS) will save in your working directory |
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| + | :4) To view your DEM double-click on the DEM to open the Foreign Collection window. |
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| − | Constraints |
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| + | [[File:ForeignCollectionWindow.png|500px]] |
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| − | 1) Buitup |
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| + | ''Figure 4 - ILWIS foreign collection window'' |
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| − | Landfill site must be far from developed areas |
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| − | 2) Wetlands |
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| + | :5) In the foreign collection window, double-click on the raster layer icon to open the DEM. |
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| − | Landfill site activities must be excluded from wetlands |
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| + | :::: [[File:ForeignCollectionWindow2.png|100px]] |
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| + | :::: ''Figure 5 - ILWIS raster icon'' |
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| − | ===About ILWIS=== |
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| − | ILWIS is an acronym for the Integrated Land and Water Information System. It is a Geographic Information System (GIS) with Image Processing capabilities. ILWIS has been developed by the International Institute for Aerospace Survey and Earth Sciences (ITC), Enschede, The Netherlands. ILWIS 3.08.01, the most recent version is open source software and can be downloaded for free from [http://52north.org/communities/ilwis/ilwis-open/download/ 52 North]. As a GIS package, ILWIS allows you to input, manage, analyze and present geo-graphical data. ILWIS uses vector and raster data, but most of the analysis is done in raster. This tutorial gives an overview of the steps required in carrying out SMCE analysis in ILWIS using landfill site selection as practical example. |
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| + | ::* The raster you have imported will open |
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| − | [[File:ilwis_52n_38_300.jpg]] |
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| + | [[File:OpenMap_2.png|800px]] |
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| − | ===Getting Started=== |
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| − | Before starting the SMCE analysis, create your working folder and ensure all data needed for the exercise are in the folder. |
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| + | ''Figure 6 - Projected DEM of Lake Okanagan in ILWIS software'' |
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| − | ===Starting ILWIS=== |
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| − | *Ensure that ILWIS is properly installed on your computer |
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| − | *Locate ILWIS from the Program list and double click on the icon [[File:icon.jpg]] to launch the program. |
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| − | *Once the software is initiated, ILWIS main page will open |
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| − | *Use the ILWIS Navigator Tab to locate your working folder. The Navigator lists all drivers and directories. |
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| − | [[Image:ILWIS_Interface.bmp|400px]] Figure 2: Screenshot of ILWIS Interface |
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| − | === |
+ | ===Projecting a DEM=== |
| + | In this version of ILWIS 3, you are able to change the projection of the DEM without problems. This step is important, especially when working with data from multiple sources as they will often not use the same projection. The following steps explain how to find the current projection of the DEM, create a new projection, and then change the projection of the existing DEM. |
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| − | 1) Set Data path/project environment by clicking on Navigator button to browse to the working folder |
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| + | (note: For the following hydrological analyses, the coordinate system chosen needs to be in planar coordinates (units of metres), not in polar coordinates (units of degrees)) |
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| − | 2) Click File and navigate to import and via Geospatial Data Abstraction Library (GDAL) |
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| + | ====Determining the Current Coordinate System==== |
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| − | 3) Click Vector and change the format type to ESRI shapefile |
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| + | :1) Right click on the raster, and select Properties. |
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| + | [[File:CurrentCoordSystem_1.1.png|800px]] |
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| − | 4) Click on Input tab to choose the shapefile to be imported from the working folder |
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| + | ''Figure 7 - Path to find properties of a raster'' |
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| − | 5) Give Output name and click OK to open the map |
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| − | 6) Repeat steps 1-5 to import other data into the ILWIS environment |
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| + | ::* The Properties of Raster Map window will open. Read the line that says: Coordinate System (see Figure 8 below). |
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| − | [[Image:import.bmp|400px]] |
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| + | ::* This tells you which Coordinate System file is currently being used by the raster. In this example, the Coordinate System file called "dem" is being used. |
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| − | Following are the data imported to ILWIS interface |
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| + | [[File:CurrentCoordSystem_2.111.png|300px]] |
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| − | [[Image:city_Ottawa.png|400px]] Figure 3: Screenshot of Boundary of City of Ottawa |
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| − | |||
| − | [[Image:wetlands.png|400px]] Figure 4: Screenshot of Wetlands |
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| + | ''Figure 8 - Properties of Raster Map window with arrow pointing to the current Coordinate System in use'' |
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| − | [[Image:road.png|400px]] Figure 5: Screenshot of Major Road |
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| − | [[Image:contour.png|400px]] Figure 6: Screenshot of Contour |
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| + | :2) Close the Properties of Raster Map window. |
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| − | [[Image:builtup.png|400px]] Figure 7:Screenshot of Builtup |
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| + | :3) Right click on the coordinate system in use by the raster, and select Properties. |
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| − | [[Image:waterbody.png|400px]] Figure 8: Screenshot of Waterbody |
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| + | :::: [[File:CurrentCoordSystem_3.png|100px]] |
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| − | ===Creating Coordinate System=== |
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| + | :::: ''Figure 9 - ILWIS coordinate system icon'' |
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| − | The vector datasets for this exercise were in different coordinate systems and for a successful SMCE analysis, there is need to assign the same coordinate system and geo-referencing to all input data. |
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| + | [[File:CurrentCoordSystem_1.png|300px]] |
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| − | To assign coordinate system, follow the following steps: |
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| + | ''Figure 10 - Path to find properties of a coordinate system'' |
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| − | 1) Go to ILWIS main interface |
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| − | 2) Click File and scroll to Create and choose Coordinate System |
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| + | ::* The Properties of Coordinate System LatLon window will open. |
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| − | [[Image:coord1.png|400px]] |
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| + | ::* This tells you which coordinate system is current being used by the Coordinate System file and the raster. In this example, the reference coordinate system being used is WGS 1984. |
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| − | 3) Give Name, select CoordSystem Projection and click OK |
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| − | [[ |
+ | [[File:CurrentCoordSystem_2.png|300px]] |
| + | ''Figure 11 - Properties of Coordinate System LatLon window'' |
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| − | 4) Select the suitable Projection and click OK |
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| − | [[Image:coord3.png|400px]] |
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| + | ====Creating a New Coordinate System==== |
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| − | 5) Click the Ellipsoid tab, select the appropriate Ellipsoid and click OK |
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| + | :1) Click File --> Create --> Coordinate System |
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| − | [[ |
+ | [[File:CreateCoordSystem_1.png|800px]] |
| + | ''Figure 12 - Path to find properties of a coordinate system'' |
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| − | 6) Click on Datum tab, select the appropriate Datum and click OK |
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| − | [[Image:coord5.png|400px]] |
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| + | ::* The Create Coordinate System window will open. |
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| − | 7) Enter the suitable Zone (if necessary) |
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| − | [[ |
+ | [[File:CreateCoordSystem_2.png|300px]] |
| + | ''Figure 13 - Create Coordinate System window'' |
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| − | '''Assigning Coordinate to Vector datasets''' |
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| + | :2) Input a name for the new coordinate system, and select CoordSystem Projection. Press OK. |
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| − | 1) Right click on the vector data and choose properties |
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| + | ::* The Coordinate System Projection window will open. Click Projection. |
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| − | [[Image:coord_vector1.png|400px]] |
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| + | [[File:CreateCoordSystem_3.png|300px]] |
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| − | 2) Change the Coordinate system to the one created earlier (Zone18) |
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| + | ''Figure 14 - Coordinate System Projection window'' |
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| − | [[Image:coord_vector2.png|400px]] |
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| − | 3) Click Apply and OK |
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| + | ::* The Select Projection window will open. |
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| − | [[Image:coord_vector3.png|400px]] |
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| + | [[File:CreateCoordSystem_4.png|300px]] |
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| − | 4) Repeat steps 1-3 for all the vector datasets |
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| + | ''Figure 15 - Select Projection window'' |
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| − | ===Vector to Raster=== |
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| − | Since the Spatial Multiple Criteria Evaluation analysis will be done using raster data; hence there is need to convert all input data to raster. For vector to raster data conversion, follow the steps below: |
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| − | 1) Click with the right mouse button on the vector map and select ‘Polygon to Raster’ from the menu |
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| + | :3) Double-click the projection you would like to use from the list. In this case the Universal Transverse Mercator (UTM) projection was selected. |
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| − | [[Image:V_Raster1.png|400px]] |
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| + | ::* The Coordinate System Projection window will open again, this time with more options. |
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| − | 2) Click on the button beside GeoReference Tab |
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| + | [[File:CreateCoordSystem_8.png|300px]] |
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| − | [[Image:V_Raster2.bmp|400px]] |
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| + | ''Figure 16 - Updated Coordinate System Projection window'' |
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| − | 3) Give a GeoReference Name (Ottawa_n) |
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| − | 4) Click the Coordinate System drop down and choose coordinate system (Zone 18) created earlier |
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| + | :4) Click Datum. |
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| − | [[Image:V_Raster3.png|400px]] |
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| + | ::* The Select Datum window will open. |
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| − | 5) Click show to open the raster data |
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| + | [[File:CreateCoordSystem_6.png|300px]] |
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| − | 6) To ensure the all input data have the same GeoReference, use the GeoReference (Ottawa_n) created in steps 2-4 when converting other vector data to raster. |
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| + | ''Figure 17 - Select Datum window'' |
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| − | [[Image:V_Raster4.png|400px]] |
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| − | ===Creating Buffer=== |
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| − | Parts of the criteria set for sitting the landfill are proximities to major roads and water-bodies; therefore buffers are to be created around major roads and water-bodies. To create buffer in ILWIS, follow the steps below: |
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| + | :5) Choose the geodetic datum coordinate system from the list, and the Area for the datum if available. In this case, North American 1983 (NAD 83) and the Canada was selected as the area. |
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| − | 1) Right click on the raster data and scroll to Raster Operations, then choose Distance Calculation |
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| + | ::* Again, the Coordinate System Projection window will open, this time with more changes. |
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| − | [[Image:buffer1.png|400px]] |
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| + | [[File:CreateCoordSystem_7.png|300px]] |
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| − | 2) Give name to Output Raster Map |
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| + | ''Figure 18 - Second updated Coordinate System Projection window'' |
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| − | 3) Choose distance as Domain |
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| − | 4) Specify distance and click show to view the map |
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| + | :6) Check the Northern Hemisphere option (if applicable), and enter UTM zone that your area of interest is located in. In this case, Okanagan Lake is located in UTM zone 11. |
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| − | 5) Repeat the steps 1-4 for other data to be buffered. |
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| + | ::* If you are unsure of the UTM zone your area of interest is located within, you can go to [https://mangomap.com/robertyoung/maps/69585/What-UTM-Zone-am-I-in-# this] website. Here, you are able to enter a location and the UTM zone will be provided on the map. |
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| − | [[Image:buffer2.bmp|400px]] |
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| + | :7) Click OK. Now the new coordinate system has been created, and appears in your working folder. |
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| − | Figures below are the results of the buffer generated: |
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| + | ====Projecting a DEM into a New Coordinate System==== |
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| − | [[Image:buffer3.png|400px]] |
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| + | :1) Right click on the raster in the Foreign Collection folder, and select Properties. |
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| − | Figure 9: Screenshot showing Road Buffer |
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| + | [[File:ApplyCoordSystem_1.png|800px]] |
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| + | ''Figure 19 - Path to find properties of a raster'' |
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| − | [[Image:buffer4.png|400px]] |
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| − | Figure 10: Screenshot showing Waterbody Buffer |
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| + | ::* Again, the Properties of Raster Map window will open. |
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| − | ===Contour to DEM=== |
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| − | 1) Right click on the contour data, Scroll to Segment Operations, then Attribute Map |
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| + | :2) Click the yellow GeoReference folder. |
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| − | [[Image:Cont1.png|400px]] |
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| + | [[File:ApplyCoordSystem_2.png|500px]] |
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| − | 2) Change Attribute to the field that contain the Z values, then give name to Output Segment Map |
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| + | ''Figure 20 - Properties of Raster Map window with arrow pointing to yellow GeoReference folder'' |
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| − | [[Image:Cont2.png|400px]] |
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| − | 3) Click show to view the map |
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| + | ::* The Create Georeference window will open. |
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| − | 4) Right click on the newly created contour data (Contour_Zvalue) and scroll to Contour Interpolation |
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| + | :3) Click down-arrow for the Coordinate System menu. Select your new coordinate system from this list. |
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| − | [[Image:Cont3.png|400px]] |
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| + | [[File:ApplyCoordSystem_3.png|500px]] |
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| − | 5) Give Output name (DEM), choose the GeoReference created earlier, leave Domain as value |
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| + | ''Figure 21 - Create Georeference window with Coordinate System menu open'' |
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| − | [[Image:Cont4.png|400px]] |
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| − | 6) Click show to view the map |
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| + | :4) Press OK in the Create Georeference window. Then, Press OK in the Properties of Raster Map window. |
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| − | [[Image:New DEM.png|400px]] |
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| + | ::* Now the raster map has been projected into the new coordinate system. |
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| − | Figure 11: Screenshot showing DEM |
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| − | === |
+ | ===Fill Sinks in a DEM=== |
| + | Fills should be run on DEMs to remove any local depressions, which can cause inaccuracies in following hydrological analyses. |
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| − | ====Creating DFDX and DFDY==== |
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| + | Within ILWIS there are two Fill Methods: |
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| − | 1) Right click on DEM data, choose Image Processing>Filter |
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| + | * Fill Sinks – removes depressions that consist of a single pixel and depressions that consist of multiple pixels. These pixels will then be given the smallest value of adjacent pixels. |
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| − | [[Image:Slope1.png|400px]] |
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| + | * Cut terrain – removes the depressions, does not re-assign values to the pixels but removes them entirely from the DEM |
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| + | More information on this operation can be found at the [http://spatial-analyst.net/ILWIS/htm/ilwisapp/fill_sinks_functionality.htm ILWIS Fill Sinks] web page. |
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| − | 2) Choose Linear as Filter Type and Filter name to DFDX |
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| + | :1) Right click on the raster layer in which the sinks have been filled, and select DEM Hydro-processing --> Fill Sinks. |
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| − | 3) Give Output name and click show to view the map |
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| − | [[ |
+ | [[File:FillSinks_DropdownMenu.png|500px]] |
| + | ''Figure 22 - Path to the Fill Sink operation'' |
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| − | 4) Repeat the same process to create DFDY |
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| − | [[Image:Slope3.png|400px]] |
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| + | ::* The Fill Sinks window will open |
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| − | ====Creating Slope==== |
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| + | [[File:FillSinks_Options.png|300px]] |
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| − | 1) From the Finder Table of Content, double click Map Calculation |
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| + | ''Figure 23 - Fill Sinks window'' |
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| − | [[Image:Slope4.png|400px]] |
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| − | 2) Type this formula: 100*HYP (DX, DY)/PIXSIZE (DEM) into the Expression Space |
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| + | :2) Choose a method to fill sinks (in this case, fill sinks was selected). |
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| − | Note: Change DX, DY and DEM using your own data |
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| + | :3) Name the output raster with sinks filled, and click Show. |
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| − | 3) Give Output name and choose value as Domain |
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| + | ::* A pop-up window called the Progress Manager will open after any operation is initiated. This window tracks the progress of the operation being using a status bar that shows the status of the operation. |
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| − | 4) Click Show to view the map |
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| − | [[ |
+ | [[File:Progress_Manager.png|500px]] |
| + | ''Figure 24 - Progress Manager window'' |
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| − | [[Image:Slope6.png|400px]] |
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| − | Figure 12: Screenshot showing Derived Slope |
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| + | :4) Once the operation is completed, the Progress Manager window will close. The raster with sinks filled will save in the foreign collection folder and open in a new window. |
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| − | ====Creating Domain for Slope Classification==== |
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| + | [[File:FillSinks_DEM.png|800px]] |
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| − | 1) Click File, then Create and click on Domain |
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| + | ''Figure 25 - Map of Lake Okanagan with sinks filled'' |
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| − | [[Image:Slope7.png|400px]] |
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| − | 2) Give Domain Name, Check Class and Group |
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| + | ===Flow Direction=== |
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| − | 3) Click Ok to Continue |
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| + | Flow direction depicts a main direction of flow (run-off). The flow direction operation determines into which neighbouring pixel any water from a given pixel would flow. This is determined by a moving 3x3 window for every single pixel, based on its neighbouring pixels height values. |
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| − | [[Image:Slope8.png|400px]] |
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| + | Flow direction can be calculated by two methods: |
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| − | 4) Click on add Item to add all classes |
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| + | * Steepest Slope: finds steepest slope of a central pixel to one of its 8 neighbouring pixels |
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| − | [[Image:Slope9.png|400px]] |
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| + | * Lowest height: finds the neighbouring pixel with the smallest height value |
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| + | |||
| + | More information on the methods can be found at the [http://spatial-analyst.net/ILWIS/htm/ilwisapp/flow_direction_functionality.htm ILWIS Flow Direction] web page. |
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| + | :1) Right click on the raster layer in which the sinks have been filled, and select DEM Hydro-processing --> Flow Direction |
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| − | [[Image:Slope10.png|400px]] |
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| − | [[ |
+ | [[File:FlowDir_DropdownMenu.png |500px]] |
| + | ''Figure 26 - Path to the Flow Direction operation '' |
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| − | ====Combining Slope with Domain==== |
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| − | 1) Right click on the Slope data, Go to Image Processing and Click on Slicing |
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| + | ::* The Flow Direction window will open |
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| − | [[Image:Slope12.png|400px]] |
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| + | [[File:FlowDir_Options.png |300px]] |
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| − | 2) Give Output Name and Choose Domain created earlier as Domain (Slope_class) |
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| + | ''Figure 27 - Flow Direction window'' |
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| − | [[Image:Slope13.png|400px]] |
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| − | 3) Click Show to view the Slope Classification Map |
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| + | :2) Choose a flow direction method (in this case, steepest slope was selected) |
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| − | [[Image:Slope14.png|400px]] |
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| + | :3) Name the output flow direction raster, and click Show |
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| − | Figure 13: Screenshot showing Slope Classification |
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| + | :4) The flow direction raster will save in the foreign collection folder and open in a new window |
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| − | ===Spatial Multi-Criteria Evaluation Analysis=== |
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| − | ====Getting Started with SMCE==== |
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| + | [[File:FlowDir_DEM.png| 800px]] |
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| − | 1) From the Operation Tree, double click on Spatial Multi-Criteria Evaluation |
||
| + | ''Figure 28 - Flow Direction map for Lake Okanagan'' |
||
| − | [[File:SMCE1n.bmp|400px]] |
||
| + | ===Flow Accumulation Map=== |
||
| − | 2) Both the Problem Analysis and Decision Making modules will be used to find the suitable Landfill sites |
||
| + | Flow Accumulation performs a cumulative count of the number of pixels that would flow into any given cell on the way to an outlet. This operation is commonly used to determine potential drainage patterns of terrain. |
||
| − | 3) Select on Problem Analysis and click OK to open the SMCE workspace |
||
| + | Flow Accumulation is calculated from the map created in Flow Direction, counting the number of cells that would drain into outlets based on the flow direction. |
||
| − | [[File:SMCE2.bmp|400px]] |
||
| + | |||
| + | More information on the method can be found at this [http://spatial-analyst.net/ILWIS/htm/ilwisapp/flow_accumulation_functionality.htm ILWIS Flow Accumulation webpage] |
||
| + | :1) Right click on the raster layer in which the flow direction has been calculated, and select DEM Hydro-processing --> Flow Accumulation |
||
| − | [[File:SMCE3.png|400px]] |
||
| + | [[File:FlowAcc_DropdownMenu.png]] |
||
| − | 4) Click File>Save to save the SMCE project |
||
| + | ''Figure 29 - Path to the Flow Accumulation operation'' |
||
| − | 5) Double click on New Goal to rename it and click on ‘filename given’ to give output name |
||
| − | [[File:SMCE4.png|400px]] |
||
| + | ::* The Flow Accumulation window will open |
||
| − | ==== Adding factors and constraints data==== |
||
| + | [[File:FlowAcc_Options.png]] |
||
| − | 1) Click on insert Spatial Factor icon or click Edit>Insert>Spatial Factor to inset all 'Factors' data |
||
| + | ''Figure 30 - Flow Accumulation window'' |
||
| − | [[Image:Factor1.png|400px]] |
||
| − | [[Image:Factor2.png|400px]] |
||
| + | :2) Name the output Flow Accumulation raster, and click Show |
||
| − | 2) Click on Insert Spatial Constraint icon or click Edit>Insert>Spatial Constraint to insert all 'Constraints' data |
||
| + | :3) The flow accumulation raster will save in the foreign collection folder and open in a new window |
||
| − | [[Image:Factor3.bmp|400px]] |
||
| − | [[ |
+ | [[File:FlowAcc_DEM.png| 800px]] |
| + | ''Figure 31 - Flow Accumulation map for Lake Okanagan'' |
||
| − | ====Standardize factors and constraints==== |
||
| − | 1) To standardize factors, change to Multi Criteria Analysis Mode |
||
| + | ::*The output map will appear to be almost one uniform colour. If you use the zoom-in tool [[File:ILWIS zoom tool.png]] you can see more defined stream networks. |
||
| − | [[Image:Standard1.png|400px]] |
||
| + | ::* Legend values can be seen by expanding the menu on the left of the map in the map window |
||
| − | 2) Right click on the factor data and choose standardize |
||
| − | [[ |
+ | [[File:FlowAcc_ZoomDEM.png|800px]] |
| + | ''Figure 32 - Zoomed in view of flow in the Lake Okanagan Flow Accumulation map'' |
||
| − | 3) To create standard for slope, enter the minimum and maximum suitable slope values |
||
| − | [[Image:Standard3.png|400px]] |
||
| + | ===Drainage Network=== |
||
| + | ====Drainage Network Extraction==== |
||
| − | 4) To standardize the road data, right click on the road raster data and choose standardize. |
||
| + | The '''Drainage Network Extraction''' operation extracts a drainage network map. The map is boolean and will illustrate the drainage as pixels with value True, while all other pixels have value of False. The pixel value is determined by the '''Flow Accumulation Map''' and a threshold value. The threshold value in this operation is the minimum value required for a flow to be considered True in a drainage network, all cells with a value lower than the threshold will be classified as False. |
||
| − | 5) Here, I chose Cost and Goal as Method and entered range scores |
||
| + | More information on the operation can be found at the [http://spatial-analyst.net/ILWIS/htm/ilwisapp/drainage_network_extraction.htm Drainage Network Extraction webpage] |
||
| − | [[Image:Standard4.png|400px]] |
||
| + | :1) Right click on the raster layer in which the flow accumulation has been calculated, and select DEM Hydro-processing --> Drainage Network Extraction |
||
| − | 6) Repeat the same steps to standardize waterbody |
||
| − | [[ |
+ | [[File:DrainNetExtract_DropdownMenu.png |500px]] |
| + | ''Figure 33 - Path to the Drainage Network Extraction operation'' |
||
| − | ====Assigning weight (Pairwise)==== |
||
| − | 1) To assign weight, right click on the goal name (Landfill) under ‘Criteria Tree’ and choose Weigh or click on Weigh icon. |
||
| + | ::* The Drainage Network Extraction window will open |
||
| − | [[Image:Weight1.bmp|400px]] |
||
| + | [[File:DrainNetExtract_Options.png|400px]] |
||
| − | 2) I chose the Interactive ‘Pairwise Method’ and clicked Ok to continue |
||
| + | 'Figure 34 - Drainage Network Extraction window'' |
||
| − | Below are the weights assigned to each factor: |
||
| − | 3) Here, I clicked the drop down box and I chose ‘Road is moderately less important than Lake |
||
| + | :2) Determine desired threshold value (in this case, 10000 was the threshold) |
||
| − | [[Image:Weight2.png|400px]] |
||
| − | + | :3) Name the output drainage network raster, and click Show |
|
| + | :4) The drainage network map containing all streams that meet the threshold value will open |
||
| − | [[Image:Weight3.png|400px]] |
||
| − | [[ |
+ | [[File:DrainNetExtract_Dem.png| 800px]] |
| + | ''Figure 35 - Drainage Network map of Lake Okanagan region'' |
||
| − | Note: There are other two methods of assigning weights which also be used |
||
| − | Pairwise Comparison Results |
||
| + | ::* Again, using the zoom-in tool will allow you to see the drainage network more clearly |
||
| − | [[ |
+ | [[File:DrainNetExtract_ZoomDEM.png|800px]] |
| + | ''Figure 36 - Drainage Network map of Lake Okanagan region zoomed in'' |
||
| − | ====Running Spatial Multi Criteria Evaluation Module==== |
||
| − | 1) To run the SMCE module to create the suitability map for Landfill, click on Generate and choose ‘All Output’ |
||
| + | ====Drainage Network Ordering==== |
||
| − | [[Image:SMCE_1.png|400px]] |
||
| + | The '''Drainage Network Ordering''' operation finds all drainage lines and nodes in the '''Drainage Network''', and applies a unique ID to each stream. |
||
| − | 2) Wait a while for the analysis to finish and click Ok to view the map |
||
| + | Drainage Network Ordering requires the input of: |
||
| − | [[Image:Landfill1.bmp|400px]] |
||
| + | * A Filled DEM; |
||
| − | Figure 14: Screenshot showing Suitable Landfill Sites |
||
| + | * A Flow Direction Map; and, |
||
| + | * A Extracted Drainage Network Map. |
||
| + | More information on the operation can be found at the [http://spatial-analyst.net/ILWIS/htm/ilwisapp/drainage_network_ordering.htm Drainage Network Ordering webpage]. |
||
| − | ====Interpretation of Result==== |
||
| + | ---- |
||
| − | SMCE map shows values ranging from 0-1; a value of 0 denoted with colour Red indicates less suitable areas. The more the values move towards 1, the more acceptable such areas are, i.e. transitions from Yellow to lemon and finally Green indicates the most suitable sites. |
||
| + | ''' Please note: In version 3.8.5 of ILWIS, the Drainage Network Order operation did not produce any values in the attribute table. Therefore, the drainage network order was not produced. I have chosen to include Figure 39 and 40 to provide an example of what ''should'' have happened in the event that an update is provided for ILWIS 3 in the future, and this operation is debugged.''' |
||
| − | ==Conclusion== |
||
| + | ---- |
||
| − | This tutorial showed the steps required for suitability mapping for landfill in the City of Ottawa, using the analytical functions of SMCE module in ILWIS software. Decision Tree wizard was used to add factors and constraints; to standardize and assign weights to the constraints and factors for successful execution of the decision processes. Finally, SMCE analysis was carried out to derive the suitability map for the landfill. |
||
| + | :1) Right click on the raster layer in which the sinks have been filled, and select DEM Hydro-processing --> Drainage Network Ordering. |
||
| − | ==References== |
||
| − | *Agus (2011), Modeling Spatial Analysis for Identifying Landslides Areas in Sumedang |
||
| − | http://www.scribd.com/doc/76923076/Analysis-spatial-using-ILWIS |
||
| + | [[File:DrainNetOrder_DropdownMenu.png |500px]] |
||
| − | *Mohammed A. Sharifi and Vasilios Retsios,(2004), Site selection for waste disposal through spatial multiple criteria decision analysis |
||
| − | http://www.itl.waw.pl/czasopisma/JTIT/2004/3/28.pdf |
||
| + | ''Figure 37 - Path to the Drainage Network Ordering operation'' |
||
| − | * Multi Hazard Risk Assessment |
||
| + | |||
| − | http://www.ecapra.org/sites/default/files/documents/Book%20Multi%20Hazard%20Risk%20Assessment_0.pdf |
||
| + | |||
| + | ::* The Drainage Network Ordering window will open. |
||
| + | |||
| + | :2) Input the previously created flow direction map, the extracted drainage network map, and name the output raster map. |
||
| + | |||
| + | [[File:DrainNetOrder_Options.png |300px]] |
||
| + | |||
| + | ''Figure 38 - Drainage Network Ordering Window'' |
||
| + | |||
| + | |||
| + | :3) Input a value for the minimum drainage length (in this case, 1000). Press Show. |
||
| + | |||
| + | ::* Minimum drainage length determines the minimum length a drainage line in the extracted drainage network map that can be assigned an unique ID. |
||
| + | |||
| + | ::* The output drainage network order map will open. |
||
| + | |||
| + | [[File:Drainage Network Ordering output map.png|800px]] |
||
| + | |||
| + | ''Figure 39 - Drainage Network Ordering output map'' |
||
| + | |||
| + | |||
| + | Output consists of both a map and a Table. The table lists all the ''streams'' with ID values, coordinates, lengths, slope of drainage. This can be seen in Figure 40. |
||
| + | |||
| + | [[File:Drainage network Order.png|900px]] |
||
| + | |||
| + | ''Figure 40 - Drainage Network Order output table'' |
||
| + | |||
| + | |||
| + | ===DEM Visualization=== |
||
| + | |||
| + | The '''DEM Visualization''' operation creates a colour composite raster by creating three shadow maps (from the West, North-West, and North directions). These shadow maps are then laid over one another, and the colour composite is created. Used in combination with the filled DEM, the relief of the area of interest can be examined. |
||
| + | |||
| + | More information on the DEM Visualization operation can be found at the [http://spatial-analyst.net/ILWIS/htm/ilwisapp/dem_visualization.htm DEM Visualization] web page. |
||
| + | |||
| + | :1) Click on Operations --> DEM hydro-processing --> DEM Visualization |
||
| + | |||
| + | [[File:DEMVisualization_DropdownMenu.png|800px]] |
||
| + | |||
| + | ''Figure 41 - Path to DEM Visualization operation'' |
||
| + | |||
| + | |||
| + | ::* The DEM Visualization window will open. |
||
| + | |||
| + | :2) Input the filled DEM as the input DEM, and name the output map. Click OK. |
||
| + | |||
| + | [[File:DEMVisualization_Options.png|300px]] |
||
| + | |||
| + | ''Figure 42 - The DEM Visualization window'' |
||
| + | |||
| + | |||
| + | ::* The DEM Visualization raster map will open. |
||
| + | |||
| + | [[File:DEMVisualization_DEM.png|800px]] |
||
| + | |||
| + | ''Figure 43 - The DEM Visualization raster map'' |
||
| + | |||
| + | |||
| + | :3) Click Layers --> Add Layer. |
||
| + | |||
| + | [[File:DEMVisualization_AddLayer.png|800px]] |
||
| + | |||
| + | ''Figure 44 - Path to add a layer on a raster'' |
||
| + | |||
| + | |||
| + | ::* The Add Data Layer window will open. |
||
| + | |||
| + | :4) Select the filled DEM to add it as a layer on your map. Press OK. |
||
| + | |||
| + | [[File:DEMVisualization_LayerOptions.png|500px]] |
||
| + | |||
| + | ''Figure 45 - The Add Data Layer window'' |
||
| + | |||
| + | |||
| + | ::* The filled DEM layer will appear on top of the DEM visualization layer. |
||
| + | |||
| + | :5) Expand the information about the filled DEM layer on the left-side of the screen by pressing the + button beside the layer name. Then expand the Display Tools option. Next, expand the Portrayal option. |
||
| + | |||
| + | [[File:DEMVisualization_Expand2.png|800px]] |
||
| + | |||
| + | ''Figure 46 - The expanded options for the filled DEM layer'' |
||
| + | |||
| + | |||
| + | :6) Double-click on Representation and change the Representation to Green-Brown. Click Apply, then Close. |
||
| + | |||
| + | ::* The Set Representation window will open. |
||
| + | |||
| + | [[File:DEMVisualization_SetRep.png|300px]] |
||
| + | |||
| + | ''Figure 47 - The Set Representation window'' |
||
| + | |||
| + | |||
| + | :7) Double-click on the Transparency options for the filled DEM layer on the left-side of the screen. |
||
| + | |||
| + | [[File:DEMVisualization_Transpar.png|800px]] |
||
| + | |||
| + | ''Figure 48 - Location of the Transparency option on the left toolbar'' |
||
| + | |||
| + | |||
| + | ::* The Transparency window will open. |
||
| + | |||
| + | |||
| + | [[File:DEMVisualization_SetTranspar.png|300px]] |
||
| + | |||
| + | ''Figure 49 - The Transparency window'' |
||
| + | |||
| + | |||
| + | :8) Change the transparency by dragging the pointer to 70, or by typing 70 into the box. Press Apply, then Close. |
||
| + | |||
| + | ::* The final visualized DEM is now ready. This layer now shows clearly the hydrological features of the location of interest. |
||
| + | |||
| + | [[File:DEMVisualization_FinalDEM.png|800px]] |
||
| + | |||
| + | ''Figure 50 - The final visualized DEM raster map'' |
||
| + | |||
| + | ---- |
||
| + | |||
| + | ''' At this point, the Strahler stream order could be added as an addition layer to definitively show the hydrological features according to the analyses completed before. Because this version of ILWIS is unable to complete the Drainage Network Order operation, this is not included in this tutorial. However, step-by-step instructions for adding this layer as well can be found at [http://spatial-analyst.net/ILWIS/htm/ilwisapp/dem_visualization.htm this] web page. ''' |
||
| + | |||
| + | ---- |
||
| + | |||
| + | :9) To save the this visualization of the area of interest, press File --> Save View As. |
||
| + | |||
| + | ::* The Save View As window will open. |
||
| + | |||
| + | :10) Enter a name for your map file, and a title. Click OK. |
||
| + | |||
| + | [[File:DEMVisualization_SaveOptions.png|300px]] |
||
| + | |||
| + | ''Figure 50 - The Save View As window'' |
||
| + | |||
| + | |||
| + | ::* The view will be saved in the working folder for the analysis. |
||
| + | |||
| + | ===Overland Flow Length=== |
||
| + | |||
| + | The '''Overland Flow Length''' operation measures the overland distance towards the 'nearest' drainage location for each pixel based on flow paths available from the '''Flow Direction Map'''. This will create a map showing the distance a flow must travel to reach the outlet of a given watershed. |
||
| + | |||
| + | More information on Overland Flow Length that can be found at the [http://spatial-analyst.net/ILWIS/htm/ilwisapp/overland_flow_length.htm ILWIS Overland Flow Length webpage] |
||
| + | |||
| + | ---- |
||
| + | |||
| + | ''' Please note: In version 3.8.5 of ILWIS, the Drainage Network Order operation did not produce any values in the attribute table. Therefore, the drainage network order was not produced. I have chosen to include the figures below to provide an example of what ''should'' have happened in the event that an update is provided for ILWIS 3 in the future, and this operation is debugged.''' |
||
| + | |||
| + | ---- |
||
| + | |||
| + | :1) Right click on the DEM layer in which the drainage network order has been calculated, and select DEM Hydro-processing --> Overland Flow Length''' |
||
| + | |||
| + | [[File:OverlandFlowLength_DropdownMenu.png]] |
||
| + | |||
| + | ''Figure 51 - Path to the Overland Flow Length operation'' |
||
| + | |||
| + | |||
| + | ::* The Overland Flow Length window will open |
||
| + | |||
| + | [[File:OverlandFlowLength_DropdownMenu.png]] |
||
| + | |||
| + | ''Figure 52 - Overland Flow Length window'' |
||
| + | |||
| + | |||
| + | :2) Input the raster in which flow direction has been calculated as the Flow Direction Map, and name the output raster. Click Show. |
||
| + | |||
| + | [[File:FLow length map ILWIS.png]] |
||
| + | |||
| + | ''Figure 53 - Flow length in metres map for Lake Okanagan region'' |
||
| + | |||
| + | |||
| + | The output map will show the different sub watershed and the flow length for each cell to reach the outlet. |
||
| + | To determine the flow length of a specific cell, use the normal mouse cursor [[File:ILWIS mouse cursor.png]] and click on the area of interest. The flow length value in metres will appear in the table on the bottom left portion of the screen. |
||
| + | |||
| + | [[File:Specific point value flow length.png]] |
||
| + | |||
| + | ''Figure 54 - Flow length for a given point selected with the cursor'' |
||
| + | |||
| + | ===Not Covered in this Tutorial=== |
||
| + | This tutorial covers the most basic hydrological tools for a more simple and basic hydrological analysis using ILWIS. Operations that have not been covered but should be considered when desiring a more in-depth and accurate analysis include: |
||
| + | |||
| + | * Flow Modification |
||
| + | ** [http://spatial-analyst.net/ILWIS/htm/ilwisapp/dem_optimization_functionality.htm DEM Optimization] |
||
| + | ** [http://spatial-analyst.net/ILWIS/htm/ilwisapp/topological_optimization_functionality.htm Topological Optimization] |
||
| + | * [http://spatial-analyst.net/ILWIS/htm/ilwisapp/variable_threshold_computation_functionality.htm Variable Threshold Computation] |
||
| + | *Network and Catchment Extraction |
||
| + | ** [http://spatial-analyst.net/ILWIS/htm/ilwisapp/catchment_extraction_functionality.htm Catchment Extraction] |
||
| + | ** [http://spatial-analyst.net/ILWIS/htm/ilwisapp/catchment_merge_functionality.htm Watershed Merge] |
||
| + | * Compound Parameter Extraction |
||
| + | ** Flow Length to Outlet |
||
| + | ** Flow Path Longitudinal Profile |
||
| + | ** [http://spatial-analyst.net/ILWIS/htm/ilwisapp/compound_parameter_extraction.htm Compound Index Calculation] (includes the Wetness Index, Stream Power Index, and Sediment Transport Index) |
||
| + | * Statistical Parameter Extraction |
||
| + | ** [http://spatial-analyst.net/ILWIS/htm/ilwisapp/horton_statistics_functionality.htm Horton Statistics] |
||
| + | ** [http://spatial-analyst.net/ILWIS/htm/ilwisapp/aggregate_statistics.htm Aggregate Statistics] |
||
| + | ** [http://spatial-analyst.net/ILWIS/htm/ilwisapp/cumulative_hypsometric_curve.htm Cumulative Hypsometric Curve] |
||
| + | ** [http://spatial-analyst.net/ILWIS/htm/ilwisapp/class_coverage_statistics.htm Class Coverage Statistics] |
||
| + | |||
| + | ===Additional Resources=== |
||
| + | |||
| + | For additional assistance, a beginner User Guide for ILWIS can be obtained at the [https://52north.org/software/software-projects/ilwis/ilwis-3/user-guide/ 52 North Website] |
||
| + | |||
| + | Additional information on ILWIS operations can be found in this [http://spatial-analyst.net/ILWIS/htm/ilwis/appendices_ilwis_operations.htm ILWIS Operations Appendices] |
||
| + | |||
| + | ==Conclusion== |
||
| + | |||
| + | This tutorial showed the steps required to run some hydrological analyses using a DEM in ILWIS software. ILWIS software was used to reproject the DEM and run the hydrological analysis on the Lake Okanagan region. This tutorial should allow for basic hydrological analysis using ILWIS and a DEM of the study region. For a more in-depth analysis look into the topics '''not covered in this tutorial'''. |
||
| + | |||
| + | ==References== |
||
| + | ILWIS Software [https://52north.org/software/software-projects/ilwis/ ILWIS Software homepage] |
||
| − | *52 North |
||
| + | Natural Resources Canada [http://maps.canada.ca/czs/index-en.html Geospatial Data Extraction Tool] |
||
| − | http://52north.org/communities/ilwis |
||
Latest revision as of 19:32, 28 October 2019
Contents
- 1 Purpose
- 2 Introduction to ILWIS
- 3 Methods
- 3.1 Software Download and Installation
- 3.2 Data Sourcing
- 3.3 Starting ILWIS
- 3.4 Importing a DEM
- 3.5 Projecting a DEM
- 3.6 Fill Sinks in a DEM
- 3.7 Flow Direction
- 3.8 Flow Accumulation Map
- 3.9 Drainage Network
- 3.10 DEM Visualization
- 3.11 Overland Flow Length
- 3.12 Not Covered in this Tutorial
- 3.13 Additional Resources
- 4 Conclusion
- 5 References
Purpose
ILWIS Logo
This Wiki tutorial has been produced for the purpose of exploring and describing the methods used for hydrological analyses in ILWIS (a FOSS4G program). The objective of this tutorial is to provide users with a better understanding of how the hydrological analyses within ILWIS works, in addition to providing the instructions necessary to reach the desired output for their study region. Additionally, this tutorial will allow for comparison of ILWIS and SAGA GIS, using the same data for analysis as the Exploring Hydrological Analyses using SAGA GIS tutorial from 2013.
This project will focus on hydrological analysis of Okanagan Lake, a popular tourist destination in British Columbia, Canada. The tutorial will cover topics such as filling sinks, flow direction, DEM visualization and drainage network mapping through the use of ILWIS hydrological analysis tools.
Introduction to ILWIS
ILWIS stands for "Integrated Land and Water Information System". It is an open source Geographic Information System software program that was designed to be a user-friendly integrated software that contains both raster and vector processing capabilities, allowing for both analyses on remotely sensed images, vector maps and numerous spatial modeling abilities. ILWIS was developed by the International Institute for Aerospace Survey and Earth Sciences (ITC) in The Netherlands. This tutorial will focus on its ability to use Digital Elevation Models (DEMs) to run hydrological analyses of a study region. More information about this product can be found on the ILWIS Website
Methods
Software Download and Installation
ILWIS 3.8.5 can be downloaded for free from the GitHub page for 52 North. This is the most recent version of ILWIS 3 and was released on September 3, 2015. Since the release of this version, the ITC has released ILWIS 4. It is likely that new versions of ILWIS 3 will eventually stop being released, as the capabilities of ILWIS 4 become greater. More information about ILWIS 4 can be found on the ILWIS 4 website.
Data Sourcing
In order to carry out this exercise, a DEM of the area of interest is needed. For this project an open data DEM was obtained using the Geospatial Data Extraction Tool created by Natural Resources Canada.
Digital Elevation Models for locations outside of Canada can be obtained using the EarthExplorer Tool created by the United States Geological Survey (USGS).
Starting ILWIS
Before starting any analysis, create a working folder and ensure all data needed are in this folder. Keeping all your data in one folder makes analyses easier.
- Ensure that ILWIS 3.8.5 is properly installed on your computer
- Locate ILWIS from the program list and double click on the icon to launch program
- ILWIS main page will open
- Use the ILWIS Navigator Tab to locate your working folder. The Navigator lists all drivers and directories.
Figure 1: Screenshot of ILWIS Interface
Importing a DEM
Before any analysis can be completed, a DEM of the region of interest must be imported into ILWIS.
- 1) Click Operations --> Import/Export --> GDAL (Geospatial Data Abstraction Library)
Figure 2 - Finding the import tool in ILWIS
- An Import window will open
Figure 3 - ILWIS import window
- 2) Click to the DEM you want to import and ensure that the import format is set to Use GDAL.
- 3) Give your Output DEM a name and click OK.
- The new DEM (compatible in ILWIS) will save in your working directory
- 4) To view your DEM double-click on the DEM to open the Foreign Collection window.
Figure 4 - ILWIS foreign collection window
- 5) In the foreign collection window, double-click on the raster layer icon to open the DEM.
- Figure 5 - ILWIS raster icon
- The raster you have imported will open
Figure 6 - Projected DEM of Lake Okanagan in ILWIS software
Projecting a DEM
In this version of ILWIS 3, you are able to change the projection of the DEM without problems. This step is important, especially when working with data from multiple sources as they will often not use the same projection. The following steps explain how to find the current projection of the DEM, create a new projection, and then change the projection of the existing DEM.
(note: For the following hydrological analyses, the coordinate system chosen needs to be in planar coordinates (units of metres), not in polar coordinates (units of degrees))
Determining the Current Coordinate System
- 1) Right click on the raster, and select Properties.
Figure 7 - Path to find properties of a raster
- The Properties of Raster Map window will open. Read the line that says: Coordinate System (see Figure 8 below).
- This tells you which Coordinate System file is currently being used by the raster. In this example, the Coordinate System file called "dem" is being used.
Figure 8 - Properties of Raster Map window with arrow pointing to the current Coordinate System in use
- 2) Close the Properties of Raster Map window.
- 3) Right click on the coordinate system in use by the raster, and select Properties.
- Figure 9 - ILWIS coordinate system icon
Figure 10 - Path to find properties of a coordinate system
- The Properties of Coordinate System LatLon window will open.
- This tells you which coordinate system is current being used by the Coordinate System file and the raster. In this example, the reference coordinate system being used is WGS 1984.
Figure 11 - Properties of Coordinate System LatLon window
Creating a New Coordinate System
- 1) Click File --> Create --> Coordinate System
Figure 12 - Path to find properties of a coordinate system
- The Create Coordinate System window will open.
Figure 13 - Create Coordinate System window
- 2) Input a name for the new coordinate system, and select CoordSystem Projection. Press OK.
- The Coordinate System Projection window will open. Click Projection.
Figure 14 - Coordinate System Projection window
- The Select Projection window will open.
Figure 15 - Select Projection window
- 3) Double-click the projection you would like to use from the list. In this case the Universal Transverse Mercator (UTM) projection was selected.
- The Coordinate System Projection window will open again, this time with more options.
Figure 16 - Updated Coordinate System Projection window
- 4) Click Datum.
- The Select Datum window will open.
Figure 17 - Select Datum window
- 5) Choose the geodetic datum coordinate system from the list, and the Area for the datum if available. In this case, North American 1983 (NAD 83) and the Canada was selected as the area.
- Again, the Coordinate System Projection window will open, this time with more changes.
Figure 18 - Second updated Coordinate System Projection window
- 6) Check the Northern Hemisphere option (if applicable), and enter UTM zone that your area of interest is located in. In this case, Okanagan Lake is located in UTM zone 11.
- If you are unsure of the UTM zone your area of interest is located within, you can go to this website. Here, you are able to enter a location and the UTM zone will be provided on the map.
- 7) Click OK. Now the new coordinate system has been created, and appears in your working folder.
Projecting a DEM into a New Coordinate System
- 1) Right click on the raster in the Foreign Collection folder, and select Properties.
Figure 19 - Path to find properties of a raster
- Again, the Properties of Raster Map window will open.
- 2) Click the yellow GeoReference folder.
Figure 20 - Properties of Raster Map window with arrow pointing to yellow GeoReference folder
- The Create Georeference window will open.
- 3) Click down-arrow for the Coordinate System menu. Select your new coordinate system from this list.
Figure 21 - Create Georeference window with Coordinate System menu open
- 4) Press OK in the Create Georeference window. Then, Press OK in the Properties of Raster Map window.
- Now the raster map has been projected into the new coordinate system.
Fill Sinks in a DEM
Fills should be run on DEMs to remove any local depressions, which can cause inaccuracies in following hydrological analyses.
Within ILWIS there are two Fill Methods:
- Fill Sinks – removes depressions that consist of a single pixel and depressions that consist of multiple pixels. These pixels will then be given the smallest value of adjacent pixels.
- Cut terrain – removes the depressions, does not re-assign values to the pixels but removes them entirely from the DEM
More information on this operation can be found at the ILWIS Fill Sinks web page.
- 1) Right click on the raster layer in which the sinks have been filled, and select DEM Hydro-processing --> Fill Sinks.
Figure 22 - Path to the Fill Sink operation
- The Fill Sinks window will open
Figure 23 - Fill Sinks window
- 2) Choose a method to fill sinks (in this case, fill sinks was selected).
- 3) Name the output raster with sinks filled, and click Show.
- A pop-up window called the Progress Manager will open after any operation is initiated. This window tracks the progress of the operation being using a status bar that shows the status of the operation.
Figure 24 - Progress Manager window
- 4) Once the operation is completed, the Progress Manager window will close. The raster with sinks filled will save in the foreign collection folder and open in a new window.
Figure 25 - Map of Lake Okanagan with sinks filled
Flow Direction
Flow direction depicts a main direction of flow (run-off). The flow direction operation determines into which neighbouring pixel any water from a given pixel would flow. This is determined by a moving 3x3 window for every single pixel, based on its neighbouring pixels height values.
Flow direction can be calculated by two methods:
- Steepest Slope: finds steepest slope of a central pixel to one of its 8 neighbouring pixels
- Lowest height: finds the neighbouring pixel with the smallest height value
More information on the methods can be found at the ILWIS Flow Direction web page.
- 1) Right click on the raster layer in which the sinks have been filled, and select DEM Hydro-processing --> Flow Direction
Figure 26 - Path to the Flow Direction operation
- The Flow Direction window will open
Figure 27 - Flow Direction window
- 2) Choose a flow direction method (in this case, steepest slope was selected)
- 3) Name the output flow direction raster, and click Show
- 4) The flow direction raster will save in the foreign collection folder and open in a new window
Figure 28 - Flow Direction map for Lake Okanagan
Flow Accumulation Map
Flow Accumulation performs a cumulative count of the number of pixels that would flow into any given cell on the way to an outlet. This operation is commonly used to determine potential drainage patterns of terrain.
Flow Accumulation is calculated from the map created in Flow Direction, counting the number of cells that would drain into outlets based on the flow direction.
More information on the method can be found at this ILWIS Flow Accumulation webpage
- 1) Right click on the raster layer in which the flow direction has been calculated, and select DEM Hydro-processing --> Flow Accumulation
Figure 29 - Path to the Flow Accumulation operation
- The Flow Accumulation window will open
Figure 30 - Flow Accumulation window
- 2) Name the output Flow Accumulation raster, and click Show
- 3) The flow accumulation raster will save in the foreign collection folder and open in a new window
Figure 31 - Flow Accumulation map for Lake Okanagan
- The output map will appear to be almost one uniform colour. If you use the zoom-in tool
you can see more defined stream networks.
- The output map will appear to be almost one uniform colour. If you use the zoom-in tool
- Legend values can be seen by expanding the menu on the left of the map in the map window
Figure 32 - Zoomed in view of flow in the Lake Okanagan Flow Accumulation map
Drainage Network
Drainage Network Extraction
The Drainage Network Extraction operation extracts a drainage network map. The map is boolean and will illustrate the drainage as pixels with value True, while all other pixels have value of False. The pixel value is determined by the Flow Accumulation Map and a threshold value. The threshold value in this operation is the minimum value required for a flow to be considered True in a drainage network, all cells with a value lower than the threshold will be classified as False.
More information on the operation can be found at the Drainage Network Extraction webpage
- 1) Right click on the raster layer in which the flow accumulation has been calculated, and select DEM Hydro-processing --> Drainage Network Extraction
Figure 33 - Path to the Drainage Network Extraction operation
- The Drainage Network Extraction window will open
'Figure 34 - Drainage Network Extraction window
- 2) Determine desired threshold value (in this case, 10000 was the threshold)
- 3) Name the output drainage network raster, and click Show
- 4) The drainage network map containing all streams that meet the threshold value will open
Figure 35 - Drainage Network map of Lake Okanagan region
- Again, using the zoom-in tool will allow you to see the drainage network more clearly
Figure 36 - Drainage Network map of Lake Okanagan region zoomed in
Drainage Network Ordering
The Drainage Network Ordering operation finds all drainage lines and nodes in the Drainage Network, and applies a unique ID to each stream.
Drainage Network Ordering requires the input of:
- A Filled DEM;
- A Flow Direction Map; and,
- A Extracted Drainage Network Map.
More information on the operation can be found at the Drainage Network Ordering webpage.
Please note: In version 3.8.5 of ILWIS, the Drainage Network Order operation did not produce any values in the attribute table. Therefore, the drainage network order was not produced. I have chosen to include Figure 39 and 40 to provide an example of what should have happened in the event that an update is provided for ILWIS 3 in the future, and this operation is debugged.
- 1) Right click on the raster layer in which the sinks have been filled, and select DEM Hydro-processing --> Drainage Network Ordering.
Figure 37 - Path to the Drainage Network Ordering operation
- The Drainage Network Ordering window will open.
- 2) Input the previously created flow direction map, the extracted drainage network map, and name the output raster map.
Figure 38 - Drainage Network Ordering Window
- 3) Input a value for the minimum drainage length (in this case, 1000). Press Show.
- Minimum drainage length determines the minimum length a drainage line in the extracted drainage network map that can be assigned an unique ID.
- The output drainage network order map will open.
Figure 39 - Drainage Network Ordering output map
Output consists of both a map and a Table. The table lists all the streams with ID values, coordinates, lengths, slope of drainage. This can be seen in Figure 40.
Figure 40 - Drainage Network Order output table
DEM Visualization
The DEM Visualization operation creates a colour composite raster by creating three shadow maps (from the West, North-West, and North directions). These shadow maps are then laid over one another, and the colour composite is created. Used in combination with the filled DEM, the relief of the area of interest can be examined.
More information on the DEM Visualization operation can be found at the DEM Visualization web page.
- 1) Click on Operations --> DEM hydro-processing --> DEM Visualization
Figure 41 - Path to DEM Visualization operation
- The DEM Visualization window will open.
- 2) Input the filled DEM as the input DEM, and name the output map. Click OK.
Figure 42 - The DEM Visualization window
- The DEM Visualization raster map will open.
Figure 43 - The DEM Visualization raster map
- 3) Click Layers --> Add Layer.
Figure 44 - Path to add a layer on a raster
- The Add Data Layer window will open.
- 4) Select the filled DEM to add it as a layer on your map. Press OK.
Figure 45 - The Add Data Layer window
- The filled DEM layer will appear on top of the DEM visualization layer.
- 5) Expand the information about the filled DEM layer on the left-side of the screen by pressing the + button beside the layer name. Then expand the Display Tools option. Next, expand the Portrayal option.
Figure 46 - The expanded options for the filled DEM layer
- 6) Double-click on Representation and change the Representation to Green-Brown. Click Apply, then Close.
- The Set Representation window will open.
Figure 47 - The Set Representation window
- 7) Double-click on the Transparency options for the filled DEM layer on the left-side of the screen.
Figure 48 - Location of the Transparency option on the left toolbar
- The Transparency window will open.
Figure 49 - The Transparency window
- 8) Change the transparency by dragging the pointer to 70, or by typing 70 into the box. Press Apply, then Close.
- The final visualized DEM is now ready. This layer now shows clearly the hydrological features of the location of interest.
Figure 50 - The final visualized DEM raster map
At this point, the Strahler stream order could be added as an addition layer to definitively show the hydrological features according to the analyses completed before. Because this version of ILWIS is unable to complete the Drainage Network Order operation, this is not included in this tutorial. However, step-by-step instructions for adding this layer as well can be found at this web page.
- 9) To save the this visualization of the area of interest, press File --> Save View As.
- The Save View As window will open.
- 10) Enter a name for your map file, and a title. Click OK.
Figure 50 - The Save View As window
- The view will be saved in the working folder for the analysis.
Overland Flow Length
The Overland Flow Length operation measures the overland distance towards the 'nearest' drainage location for each pixel based on flow paths available from the Flow Direction Map. This will create a map showing the distance a flow must travel to reach the outlet of a given watershed.
More information on Overland Flow Length that can be found at the ILWIS Overland Flow Length webpage
Please note: In version 3.8.5 of ILWIS, the Drainage Network Order operation did not produce any values in the attribute table. Therefore, the drainage network order was not produced. I have chosen to include the figures below to provide an example of what should have happened in the event that an update is provided for ILWIS 3 in the future, and this operation is debugged.
- 1) Right click on the DEM layer in which the drainage network order has been calculated, and select DEM Hydro-processing --> Overland Flow Length
Figure 51 - Path to the Overland Flow Length operation
- The Overland Flow Length window will open
Figure 52 - Overland Flow Length window
- 2) Input the raster in which flow direction has been calculated as the Flow Direction Map, and name the output raster. Click Show.
Figure 53 - Flow length in metres map for Lake Okanagan region
The output map will show the different sub watershed and the flow length for each cell to reach the outlet.
To determine the flow length of a specific cell, use the normal mouse cursor 
and click on the area of interest. The flow length value in metres will appear in the table on the bottom left portion of the screen.
Figure 54 - Flow length for a given point selected with the cursor
Not Covered in this Tutorial
This tutorial covers the most basic hydrological tools for a more simple and basic hydrological analysis using ILWIS. Operations that have not been covered but should be considered when desiring a more in-depth and accurate analysis include:
- Flow Modification
- Variable Threshold Computation
- Network and Catchment Extraction
- Compound Parameter Extraction
- Flow Length to Outlet
- Flow Path Longitudinal Profile
- Compound Index Calculation (includes the Wetness Index, Stream Power Index, and Sediment Transport Index)
- Statistical Parameter Extraction
Additional Resources
For additional assistance, a beginner User Guide for ILWIS can be obtained at the 52 North Website
Additional information on ILWIS operations can be found in this ILWIS Operations Appendices
Conclusion
This tutorial showed the steps required to run some hydrological analyses using a DEM in ILWIS software. ILWIS software was used to reproject the DEM and run the hydrological analysis on the Lake Okanagan region. This tutorial should allow for basic hydrological analysis using ILWIS and a DEM of the study region. For a more in-depth analysis look into the topics not covered in this tutorial.
References
ILWIS Software ILWIS Software homepage
Natural Resources Canada Geospatial Data Extraction Tool
