Slope Calculation from Contour
Posted 24 July 2006 - 12:40 PM
Posted 24 July 2006 - 01:22 PM
Email: firstname.lastname@example.org / Twitter: @redgeographics
Posted 24 July 2006 - 01:28 PM
Posted 24 July 2006 - 02:19 PM
Posted 24 July 2006 - 04:32 PM
Posted 09 November 2006 - 06:27 PM
GRASS can do this easily. Using the v.surf.rst command you can create a DEM, Slope, and Aspect grids from your contours. The grid will be in GRASS format which isn't too handy, but then you can use r.out.gdal to output to just about any grid format you can think of.
The same is also true in ArcInfo, use the TOPOGRID command to convert the contours to a DEM and then use the SLOPE command to generate the slope grid.
Software Products Department
ESRI, Redlands, California
Posted 11 November 2006 - 08:35 AM
I use Vertical Mapper.
There are also many contour to GRID interpolation methods. To get the a good representative GRID from a set of contours I normally would use the Natural Neighbour with smoothed overshoot method. This approach rounds off hill tops. I would also include spot heights data if available to the coutours before processing.
So I believe the reason there is NO slope value on top of isolated contours is because of the interpolation method used. If the method used does not extrapolate values on hilltops, well your slope analysis is no good.
Hope this helps a bit.
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