[GRASS-user] Generating DEM from bare ground LIDAR data: v.surf.idw or v.surf.bspline ?

[Markus Metz]

stephen sefick wrote:
> I have a multitude of DEMs to generate at 1m resolution.  Are there
> any references that compare v.surf.idw and v.surf.bspline?  Any advice
> or experience with either of these two modules would be helpful.
> Which one of these modules creates the most accurate representation of
> the surface.  This will be with NC data- in fact the same 2001 data
> that is included in the new GRASS dataset.  I am working on a project
> in NC if this helps.  Thank you for all of your help, and I will
> provide any information that you may need.  Also, if I use
> v.surf.bspline is the 1.5*point average point spacing still the rule
> of thumb (the point spacing is found with running v.surf.bspline with
> the -e flag?).

The 1.5 * average point spacing is a useful rule of thumb as long as
the points are evenly spaced as e.g. for elev_lid792_bepts in the
North Carolina sample database. If the points are not evenly spaced,
e.g. strips with high density, but the strips are separated by a
distance larger than the average within-strip distance (e.g.
contours), then the spline step values need to be adjusted, no
established rule of thumb here.

We need a wiki page explaining the different interpolation methods...

Markus M

Thank you so much for all of your help.
>
> --
> Stephen Sefick
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