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I need to make an accessibility map showing the walking distance based on the terrain and availability of road networks, could anyone point me in the right direction where i could learn to do so. Basically i need to create something like this:

Map Legend

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    How does that work? What are the the axes (X and Y)? How does it deal with uphill vs downhill? – BradHards Feb 15 '14 at 8:49
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In ArcGIS, you could start with the path distance tools if you have the spatial analyst extension. The idea is to create a cost raster that reflect the difficulty to go accross a pixel (a good start is to use the time it would take you). For instance, you walk 2 times faster on a trail than out of trail. With path distance, you can also add additional horizontal and vertical factors. This is very useful in hilly terrains because moving up is not the same as moving down.

With QGIS, you can use r.walk (from GRASS). It is about the same. However, those algorithms need some tuning. And I can't tell which one is the best. This paper was also not sure about it.

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In QGIS, there is also (in addition to r.walk which @radouxju has mentioned) the Walking time plugin which you can download (Plugins > Manage and Install Plugins...). This uses the Tobler's hiking function which estimates the travel time based on data from your line layer in relation with the elevation values of the raster layer:

Walking time plugin

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    What a fascinating tool. I had no idea it was there. I'm going to have to look into the algorithm a little more closely. – WhiteboxDev Oct 14 '14 at 14:32
  • @WhiteboxDev, I find it fun to see plugins which are quite specialised. I just have to remember to disable half of them (I've downloaded more than 60) as QGIS tends to grind to a halt when it starts up! – Joseph Oct 14 '14 at 14:44

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