I'm trying to use solidworks to create a surface map.

I've started with a 3D DXF/DWG (DXF seemed to import better) which gave me a lot of imported curves on different planes.  These have been converted to sketch curves on known planes and a boundary sketch using splines placed around the four corners (map boundary is rectangular).

So far I've found a boundary surface using these four boundary sketches gives a good outline, but it seems to need countour lines in a completely different orientation to the contour lines I have.  Manually this would take a long time.

I have scan to 3D, but it requires a point cloud or mesh file.  Is there an easy way to convert the contour lines I have to a point cloud so a surface can be more automatically generated?

Is there a better approach?

Also what is the maximum volume solidworks can handle?  I'm currently working with this at a 1/1000 scale (mm instead of m) as it initially tripped beyond the modelling limits due to the altitude in the contour map.  I'm hoping that once I have created the surface I can reduce the altitude and get it under the volume limit when scaled to full size.