Hello,
I am using ArcGIS 10.1 and I am trying to use the contour tool in order to get isochrones on a time cost raster.
The raster has been estimated in the raster calculator by summing the path distance outcomes (the first one using as vertical values the Tobler's function "AWAY", so from the one point to the others; the second using the Tobler' function "TOWARDS", so from all the points to the source). The resulting raster has been converted from hours to minutes by multiplying for 60 in the raster calculator. Since I would know how many time it takes to reach a specific land portion or other points, I generated the contour lines at the intervals of 30 (minuntes, in this case) in order to get a visual insight about that.
The problem is that the contour lines consider as reachable in the same minute range also point placed at several kilometres away from the source point. To make clear, in the attached image, the blue contour line considers as reachable in 90 minutes the cell raster placed at 40 km from the source point (blue point).
How is it possible? I presume that it occurred some problem in the contour/surface raster estimation.
Has someone some clue or suggestion?
Thank you in advance.
