Hi,

I am currently attempting to test the feasibility of a navigation solution that can calculate the best route to a destination based on fuel economy variables. It is my intention to calculate an impedance value based on said variables. One of the variables I have selected is slope as a vehicle travelling uphill will use more fuel then one travelling downhill.

I have downloaded and imported into ArcMap 10.1 the Ordnance Survey ITN. However, I cannot seem to work out a way of getting slope direction from a raster underneath the roads and storing it in such a way that can be used for an impedance calculation.

I have a moderate amount of experience with ArcMap and some programming experience but I could really use the help of an expert!

Thank you,

Liam.

I am currently attempting to test the feasibility of a navigation solution that can calculate the best route to a destination based on fuel economy variables. It is my intention to calculate an impedance value based on said variables. One of the variables I have selected is slope as a vehicle travelling uphill will use more fuel then one travelling downhill.

I have downloaded and imported into ArcMap 10.1 the Ordnance Survey ITN. However, I cannot seem to work out a way of getting slope direction from a raster underneath the roads and storing it in such a way that can be used for an impedance calculation.

I have a moderate amount of experience with ArcMap and some programming experience but I could really use the help of an expert!

Thank you,

Liam.

Since you have elevation data, you can use the Interpolate Shape tool (http://resources.arcgis.com/en/help/main/10.1/index.html#//00q90000006m000000) to add z-elevation to the roads feature class in your network. You could then calculate an average or maximum slope for each line feature and use this, as well as the 3D length, to calculate a new new cost attribute in your network dataset. I'm not sure what advice to give you about how to construct your cost attribute. Consider that each road segment may have some uphill and some downhill parts, some steep parts and some not-so-steep parts. The average slope of the road feature might be zero even if it contains both a steep uphill part and a steep downhill part.

Additionally, please note that you will likely encounter problems anywhere in your road network where you have bridges or tunnels, since your elevation data probably only accounts for the elevation at ground level. If your data already had Z-levels for handling bridges and tunnels, you might be able to find a way to fudge the connectivity to make these work. You might have to manually fix each one.