been scouring online for a while, I might not be using the right phrases etc but let me run through what I'm chasing and I'll see if anyone has any links for me to read up on.

I'm a surveyor, I did 2 units of real basic GIS back at uni (2D linework, some buffers etc, super basic) using arcgis so QGIS isn't totally foreign but it certainly has been a while since I've done anything with it.

I also fly uav's at work and produce georeferenced orthometric images, DEMs, point clouds etc.

I'm looking at trying to reduce the amount of physical field pickup for a feature survey plan by flying the property, tracing over the point-cloud and exporting the linework out as a DXF so I can edit it in my CAD software (12D model, not a huge following for it's drafting ability, very good for survey work though)

I've been able to do the following;

-Create a custom CRS for the map projection that we use for the bulk of our survey work and what Photoscan also uses

-Import the georeferenced orthometric photo as a raster layer

-Import the georeferenced DEM as a raster layer and set transparency to 50% so I can see my "base map" underneath

-Create and draw lines by Shapefile Layer (even if I don't fully get the fields list at this stage)

-Export the Shapefile as a DXF, with correct CRS (I know it's right as when I view it on my CAD software it sits exactly as it should, 2D anyway) with Geometry type with several types (LineString/Polygon/GeometryCollection) with "Include z-dimension" ticked

I can import it in fine, 2D sits fine, but there is no height attached. I am, probably naively, thinking that since I'm tracing over the DEM then there should be z-values attached but obviously there isn't.

Is there something I'm missing out on? Any tips or tutes out there? Thanks