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February 20, 2017 16:38
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ArcGIS cost distance raster prep
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task: create cost distance raster for each of a series of shapefile for libya using a friction layer derived from open street map road network | |
steps: | |
1. obtain street network from OSM. I got mine from here: http://download.gisgraphy.com/openstreetmap/pbf/LY.tar.bz2 | |
then used osmosis to convert pbf to xml. | |
In arc... | |
2. reclassify road network such that roads have a value of 1 and non-roads have a value of 5. I set pixel size equal to 200m x 200m | |
3. Use Cost distance tool. | |
Input: shapefile and road friction layer. | |
Parameters: I set a max distance of 200,000 because processing for the whole country was too time consuming, and may not have even been useful. | |
4. Then I reclassified each of the resulting cost distance rasters to values of 1 - 20, inversely (such that pixel values would be higher closer to the points/lines) And would add together in a normalized fashion (maybe?) | |
That is 95% on the raster creation. Then Rob put them on an online server and added them together and set slidable parameters. ( I don't know what exactly he did) | |
Optionally: | |
1. I treated population centers differently to provide nuiance and take into consideration the different sized population. | |
As far as I can tell, there is no way to mimic the cost distance spread effect to reflect shapefile table properties. | |
If that isn't clear. I mean. I wanted smaller cities to look like they had a smaller impact. | |
To do this, I divided the population shapefile into small, medium, and large cities. (arbitrary cut offs...) | |
And then ran each with a different cost distance maximum. (100k, 150k, 200k) |
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I created this model in modelbuilder. It looks crazier than I just described, but it is taking into account extents to make sure they are standard, and exporting things uniformly as geotiffs.