Convert 2D object to 3d using DTM
I have a large area, over 5000 Square mile. I have all 3D elevation points from Lidar, contours, break lines various format, like shp with attributes to CAD in 3D etc. I can easily create an STM with Bentley Descartes, creating 3D models with Contours and draping of thousand of raster images from billions of points all that in just a few minutes. Right now, I can drape my 2D object on 3D STM to create new 3d objects that way. Works great but sometime need to do a bit more and was looking at Global mapper to do some other manipulation before exporting to 3D. I tried doing the same, with small sections for testing in Global Mapper. All I manage to do is to create 3d lines but all at fixed values like all at elevation of 9 metres??? when the test site is above 500 metres... I tried export with many different format, options... but no luck... Don't know what I am doing wrong!
So 1st need to know if possible and what is the preferred export file format and procedures
2nd need to know if that procedures can be done on such large data sets.