The final preference was that the house should be within a 15 minutes walking distance to the train and bus stations. We could calculate the time taken to reach a point from another one on a road network using network analysis. However, that method would not respect an important factor in walking--elevation. This is a kind of nontrivial analysis done on a DEM. Although neither QGIS, nor PostGIS offer a solution for this type of analysis, GRASS GIS has just the tool for us. This tool creates a cost surface, which represents walking time in seconds from one or more input points. For this, GRASS needs a DEM and an additional friction map. With the friction map, we can fine-tune the analysis, giving weights to some of ...
Calculating walking times
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