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terrain model

Oct 2, 2010 at 11:23 PM

I'm interested in creating terrain profiles and cross sections, and since GIS typically doesn't use Z coordinate, I would like to know what is the best way to handle terrain's elevation? I assume I could put Z coordinate as one of the attributes for points, but would it work for polylines? I know I can show a profile just using X and Y, but I would like to create the profile from GIS data.

Oct 3, 2010 at 2:42 AM

Coordinates can support X, Y, Z and M values, but you simply have to make sure that your featureset is set up with the correct "CoordinateType" when you are creating a shapefile from scratch.  I don't think there is such a thing as shapefile with a Z but without M, but the shapefile format itself supports either XY, XYM, or XYZM.  This will not necessarilly be visible in the 2D map in any way, but you can at least use it for storing the values so that it would effectively be 3D.  Terrain rasters just have the value of each cell, and that is usually where the elevation would come from for a profile situation, and assigning the elevation to Z lets you depict the profile in the correct location on the map while allowing an alternate plot somewhere show the elevation aspects.

Ted

Oct 3, 2010 at 5:44 AM

Ok, I can see that New Coordinate() accepts those additional values. Not sure how to set up that CoordinateType, I see there's a property "CoordinateType" for featureset, but I don't know how to set it. Are there any practical samples or guidelines how to create, access and utilize Z and M coordinates and/or create terrain models from GIS data?

Oct 3, 2010 at 4:23 PM
Try reading the coordinate type after you create the featureset using coordinates with Z values and see if it shows the correct one.  I know the "SaveAs" operation checks it, but I was fuzzy on how that gets defined.  It may be automatic.

Ted

Oct 4, 2010 at 3:07 AM

I did test featuresets with X, Y, Z and X, Y, Z, M coordinates, CoordinateType shows "Regular" for both sets, no Z or M. But when I checked that test shape file with another application, Z coordinates where there correctly. So it seems to be working ok.