Cost Path Analysis of Mars using SAGA - Revision history

Pgoszt: /* Uploading Data into SAGA */

2018-12-20T22:12:01Z

Uploading Data into SAGA

2018-10-08T23:23:56Z

Advanced Cost Path Analysis Theory

2018-10-08T22:57:18Z

Reclassify

2018-10-08T22:55:28Z

Reclassify

2018-10-08T22:34:37Z

Advanced Cost Path Analysis Theory

2018-10-08T21:40:18Z

Advanced Cost Path Analysis Theory

2018-10-08T21:31:35Z

Uploading Data into Saga

2018-10-08T17:15:44Z

SAGA

2018-10-08T16:24:16Z

Background and Data

2018-10-08T15:30:28Z

Background and Data

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 Once the file is downloaded, open the SAGA software. Start with an empty startup project.
-To import the DTM, got to “File >> Grid >> Load” and navigate to where you stored the DTM. Click Open. The file might take a little while to load.
+To import the DTM, go to “File >> Grid >> Load” and navigate to where you stored the DTM. Click Open. The file might take a little while to load.
 Next, double click the file you just imported. A map should appear, and look like the image below.

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 - How to combine all datasets into one cost surface
 These two factors are the most subjective and will vary the most between different applications and scenarios. In addition to being the most subjective elements, they are the most critical elements and can dramatically alter the outcomes of the analysis. As such, the methods used to represent data within the analysis are vital.
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 - Linear-weighted combination
 Additive combination is simply adding all cost data layers into one, which is to be used as the base of the analysis. This method is the simplest and works well if all cost layers have similar influence or if the data are classed such that they represent measurable units rather than arbitrary ones.

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 [[Image:slope_reclassed_values.PNG|700px]]
 When happy with the values, click Okay on the Lookup Table window, then Okay on the tool. Below is a photo of the reclassified slope layer.
-[[Image:slope_map_reclassed.PNG]]
+[[Image:slope_map_reclassed.PNG|395px]]
 The values selected for reclassification were arbitrarily determined and will be sufficient for this process. However, determining appropriate cost values, as will be discussed later, is one of the most difficult elements of cost path analysis.

@@ Line 121: / Line 121: @@
 When happy with the values, click Okay on the Lookup Table window, then Okay on the tool. Below is a photo of the reclassified slope layer.
+[[Image:slope_map_reclassed.PNG]]
 The values selected for reclassification were arbitrarily determined and will be sufficient for this process. However, determining appropriate cost values, as will be discussed later, is one of the most difficult elements of cost path analysis.

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 Once costs have been assigned to each data layer, the next challenge is figuring out which method to use to combine them into one cost surface.
-The method used for combining data sets into a final cost surface is partially dependent on how costs were assigned to each data layer. Similarly to assigning costs, there are two main ways to combine
+The method used for combining data sets into a final cost surface is partially dependent on how costs were assigned to each data layer. Similarly to assigning costs, there are two main ways to combine data:
 - Additive combination

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 When incorporating multiple datasets into the analysis, like the ones mentioned above, new factors need to be considered. The most notable factors are:
-- how to assign costs/standardize all datasets
+- How to assign costs/standardize all datasets
-- how to combine all datasets into one cost surface
+- How to combine all datasets into one cost surface

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 =='''Basic Cost Path Analysis'''==
-==='''Uploading Data into Saga'''===
+==='''Uploading Data into SAGA'''===
 The first step of the process is to download the DTM. The DTM of NE Syrtis comes in a TIFF (.tif) file format, which is a common file type for raster data in geospatial analysis.

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 SAGA is an open source program for GIS that has a lot of capability in geoscientific analysis and has been designed for effective implementation of spatial algorithms. It features an extensive suite of tools covering raster data (called Grid data within SAGA) and operations, imagery processing, vector processing as well as some ecological and geomorphological simulations, to name a few.
-More information can be found at their [http://www.saga-gis.org/en/index.html homepage], and the latest version of the software can be [https://sourceforge.net/projects/saga-gis/ downloaded from SourceForge.]
+More information can be found at their [http://www.saga-gis.org/en/index.html homepage], and the latest version of the software can be [https://sourceforge.net/projects/saga-gis/ downloaded from SourceForge.] This tutorial uses SAGA v6.4.0.
 To see more CUOSG tutorials that have used SAGA GIS, [https://gracilis.carleton.ca/CUOSGwiki/index.php?title=Special%3ASearch&search=SAGA&go=Go click here]

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 A crucial element to note in this analysis is the type of coordinate system required.
 Any cost path analysis requires a projected coordinate system, which measures distance in units of distance (such as meters or feet), rather than a geographic coordinate system which uses angular units (degrees or radians). In this way, the analysis represents a cost associated with a consistent distance/area rather than angles, which vary in size as distance to the poles vary.
-Since we are using data from another planet, special attention must be given to the coordinate system. Fortunately, the DTM used in this example defaults comes projected in an appropriate coordinate system and is ready for our analysis.
+Since we are using data from another planet, special attention must be given to the coordinate system. Fortunately, the DTM used in this example comes projected in an appropriate coordinate system and is ready for our analysis.
 =Methods=