Traveling Salesman Problem (TSP)
Introduction
This is a Free and Open Source Software for Geospatial (FOSS4G) inspired tutorial. It focuses on Network Analysis using a Geographic Resources Analysis Support System (GRASS).
About the Tutorial
This tutorials' main aim is to be clear and understandable. I made every effort to use real data even though this presents many problems. However, it is a reality that data is dirty and software is faliable. This tutorial will be very time consuming to complete, however, you will learn alot along the way and this knowledge will easily transfer to future projects.
In this tutorial you will
- Install GRASS
- Download and prepare data
- Start a GRASS database
- Build a network and perform analysis on it
Note If the command line is not working and you don’t wish to take the time to troubleshoot this problem I have been given a great work around from my teacher Scott Mitchell. If you do not have GRASS folders set up refer to step named Getting on our way.
- 1. Launch the OSGeo4W
- 2. Type grass64 –gui and then hit enter on the keyboard. (notice there is a space between 64 and the dash)
- 3. You will see the old GRASS version load, so simply click File from the menu bar and click Quit GIS Manager.
- 4. Now in the command box type g.gui gui=wxpython&
Installation
Install OSGEO Package (30-60mins)
First, you will need to install free geospatial software. I am using GRASS 6.4.2. This can be found through the secure and trusted site of Open Source Geospatial Foundation OSGeo4w is Your Open Source Compass for Windows This package provides a set of open source geospatial software for a Win32 environment. Simply follow the directions from this site: Click Here to go to Download Page The great thing about this pkg is that is contains several versions of GRASS. So if something doesnt work in one version it might work in another.
Launch GRASS(1-1.5 hrs)
Launching GRASS Tutorial This tutorial will give you a simple walk through of GRASS allowing for an increased understanding of the software, though it is not necessary to complete it in full.
The Tutorial
Getting Started: GRASS Database (just minutes)
1. Prior to starting a GRASS session, create a New Folder named Grassdata and a second named nonGrassData. Start GRASS and once the screen opens, browse to the Grassdata folder. Ensure all file and folder names contain NO spaces, that they are short, and do not begin with numbers.
2. Push the button for Georeferenced files, name the newLocation Ottawa and then browse to the nonGrassData folder. Select the Roadways.shp file. Now click define.
3. Click on both Ottawa and then PERMANENT in each of the grey boxes and then push the ENTER GRASS button. Now we are ready to start working in GRASS.
Next:Import data files and prepare them for processing and analysis
Importing .shp
1. You now have three screens open and running under GRASS. A command line black box, a GRASS GIS Layer Manager, and a Map Display pane. In the Layer Manager window click File | Import Vector Data |Common Import Formats.
2. A GUI window will appear to lead you forward. Choose Roadways.shp from the drop down menu and push Run. If you watch the Layer Manager window it will tell you when all is complete. At the bottom of the window you will have to hit the Map Layers tab as you have been watching the command console tab.
3. Now the Roadways.shp file is loaded to the Layer Manager window simply toggle it on to view it in the Map Display window.
Next do the same for the wards.shp file.
Importing .csv
This is not as straight forward as the .shp files. You must first open the Addresses.csv file in OpenOffice Calc for editing.
When OpenOffice asks which format the file is in pick the one that has ASCII. Then toggle on: 'separted by commas' and untoggle anything else like periods or spaces ect. In the preview box at the bottom it should now display a more normal spaced looking file.
Edit all the column headings to simple, short, alphabetical names with no spaces. Delete unnessary columns. Leave the first one, pin number,addressNumber,road names and the x and y coordinate columns. You have six columns now.
The x,y columns need to be formated. You can use the 'Find and Replace' tool. First replace all commas with periods. Then right justify the x and y columns. These are necessary steps.
Save the file as a .csv. OpenOffice might say that there is a problem, just ignore it.
To bring it into GRASS:
- Click File|Import vector data|ASCII points/GRASS ASCII vector import [v.in.ascii]
Under the Required Tab:
- Browse to the file and choose it. Then back in the GUI, name the output file.
Under the Imput Format Tab:
- Change the Field Sparator to a comma ','
Under the Points Tab:
- Number of header lines to skip: 1
- Number of column used for x: 5
- Number of column used for y : 6
- Number column used for category: 1
- Hit Run
Processing in Grass
Type this in the command line box, it will adjust the region parameters.
g.region -p vect=Roadways
Next extract the location you specifically wish to focus on. In this case it will be the Somerset ward.
v.extract input=Wards output=Somerset type=area where=cat=16
Next extract the customers that are within that ward from the larger customer data set.
v.select ainput=Addresses atype=point binput=Somerset type=area output=addSomerset operator=within
Next extract the Roadways
v.overlay ainput=Roadways atype=line binput=Somerset output=SomerRoads operator=and
Network Preperation
Type this in the command line box, it will adjust the region parameters.
g.region -p vect=Somerset
Next clean the data
v.clean input=SomerRoads output=SomerRoadCl type=line tool=break,rmdupl
Extract a Start point
When you right click on the addSomerset layer in the Layer Manager window, select to veiw the Attribute table. Scroll to find the exact address you want to use and note its 'cat#', which will be the one in the first coloum for the row you choose, you will need to input that number later in the GUI. We will use the GUI for the next 2 extrations.
- Click on menue bar: Vector|Feature selection|Query with attributes
- Browse to the addSomerset file and choose it
- Name the output map as: Start
In the next tab: Selection
- types to be extracted: point
- Where conditions of SQL type: cat=40698 OR the start point you choose earlier
- click Run but do not close the window!!!
Next extract all other points minus the one we just extracted.
- All you need to do is simply toggle back to the first tab to change the output name to Customers. And then in the Selection tab, toggle on the Revese Selection option and it will do the rest.
- Hit run and close when done.
Attribute Editing
We know that the homes are not located directly on top of the roads so we must calculate and attach them to the network for processing and analysis. First we will create 3 new columns in the attribute tables and then populate them.
v.db.addcol map=Customers columns='x double precision,y double precision,dist int'
v.db.addcol map=Start columns='x double precision,y double precision,dist int'
v.to.db map=Start type=point option=coor columns=x,y
v.to.db map=Customers type=point option=coor columns=x,y
v.distance from=Start to=SomerRoadCl to_type=line upload=dist column=dist
v.distance from=Customers to=SomerRoadCl to_type=line upload=dist column=dist
Connect Customers to the Network
Once we have the distance from all points to the roads,connect all the addresses to the road-network according to a threshold (distance)
v.net input=SomerRoadCl points=Start output=network_v2 operation=connect thresh=10
v.net input=network_v2 points=Customers output=net operation=connect thresh=50
we can view information about the network
v.category TheNetwork op=report
Network Analysis Examples:Shortest path, no cost
We have a start point, now it is time to choose a destination. Once again choose the 'cat#' of an address point, as you did earlier, using the attribute table from Customers. You will view its attribute table.
v.extract input=Customers output=End type=point where=cat=44592
Data
- Go to The city of Ottawa, Open Data Site
- Download the .csv file Address Points (main) Or click this link. Note: When you unzip this file change its name to customers.csv.
- While at the same site download the Roadways.shp file and the wards2010.shp file too.
Conclusion
Contributions to This Tutorial
About This Tutorial
This tutorial was created for GEOM4008 which is part of the Geomatics program at Carleton University, located in Ottawa, Ontario, Canada.
External Links
Here is a list of links that offer additional support and information;
- Quantum GIS Web site
- Quantum GIS Wiki
- Grass GIS Web site
- Grass GIS Wiki
- Spatial Reference
References
Data
