01-30-2017 07:20 PM
I'm using the Terrain Prep Tool > Surface... > Generate Contours to generate contours in shapefile format from point cloud data (.las). I want to generate contours at 0.5m intervals but although the contour geometries are interpolated and generated OK, the height attribute values are being rounded to a whole number i.e. I am ending up with two adjacent contours with the same height value when one should be x and the other x.5.
I'm guessing there is a simple solution but I haven't been able to find it yet!!!
Solved! Go to Solution.
02-09-2017 06:25 PM
I observed the same.
I observe same:
- The height attribute written to the shape file is rounded to the nearest wholenumber
- The actual contour geometry has the correct z value against it.
Using GeoMedia – sorry I’m not familiar enough with Imagine to know if you can do the same there and I happen to know you have GeoMedia - you could update the height attribute with the z of the actual contour geometry (or delete the height attribute and simply use the z of the geometry).
(you would have to output to a read-write warehouse first)
For my quick play I used functional attribute Z(ENDPOINT(Input.Geometry)) to get the z value of the actual geometry.
Once written to a read-write database simply use Vector> Update (Attributes) to bulk update the Height field using above formula.
- Can probably use an ERDAS Imagine spatial model to correct the height attribute instead of GeoMedia (have not explored)
- GeoMedia (Grid) can generate Contours (but Imagine better at dealing with large LAS files involved)
- ER Mapper has a contouring option that I have not explored
(ER Mapper is an optional install when you install Imagine Professional)
02-10-2017 01:34 AM - edited 02-10-2017 02:09 AM
Contouring in Imagine is pretty ancient. It actually is Raster Contouring that is later converted to Vector. I guess the limitation you see is based on Raster Contour tool data type limitations - raster attributes are allowed only on Integer or so. The old world workaround for this issue was multiply all original heigths with 10 which leaded to Decimeter height definition and accuracy. If you do that and contour by intervall 5 you end up getting 0.5m contour resolution. Decimal storage used to be quite common 15 years ago in DEM deliveries just because of this issue to store data in smaller files using integers.
The Imagine Countouring tool itself is pretty cabable and works well it is just formats and units that are bit out of dated that force workarounds.
04-06-2017 06:33 AM
Thanks Stephen - this is just what we want. There is no need to submit issue by someone to formal way if issue is already addressed in forum. You can do bug report internally from information given here. Great - thanks and now waiting for fix
Fix should be simple - just allow non integer values for contours and thats it