I am using QGIS 2.6. This question is in two related parts:

I'm trying to create a raster of travel time from one point to another point travelling via the road system. Each raster pixel will roughly represent the amount of time taken to get to a given point.

Could I do this as a function of the travel-time from a number of different points? (I suppose I could using the raster calculator once I have the previous rasters.) I.e. I could estimate the total time per week if one travels to location A 5 times a week, location B 3 times a week and location C 1 time a week.

Additionally, can one incorporate a time for a given distance to the road for points that are off-road (i.e. walking distance)? I.e. an amount per metre of ground to cover the distance to the road (taking the shortest distance possible.

  • can you clarify your question a bit. What is your input data? Do you want the shortest path from locations (points) to destonation (points/polygons) via roads? (lines) or do you want all possible shortest path from each cell on a raster to each other cells, while movement is restricted to a road-classified cells only? – dof1985 Nov 21 '14 at 12:59
  • As dof1985 said, we need more information. Your initial question sounds like a simple Euclidean distance map, but then you start mentioning time. – Chris W Nov 21 '14 at 20:40
  • Hopefully that helps. I see why it was confusing; very badly written sorry. – AER Nov 21 '14 at 21:32
  • Considering a single raster, you can only look at each cell being time from a single point. With multiple points, the time value for any given cell will be from the nearest point. And there's two ways to look at the time value of the raster - time required to cross that cell (cost raster), or time needed to get to that cell from some origin (a solution/distance raster). It sounds like you're trying to blend the two and use them at the same time. Plus you're looking at distances between two points using a road (path of cells) vs off a road (time increases per cell away from the road). – Chris W Nov 22 '14 at 21:10

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