r.surf.contour time

[Justin Hickey]

Hello Stefano

I don't know if this will help you or not but the following comes from
the man page for r.surf.contour. It notes the conditions that are
required for r.surf.contour to run well.

===================================================================

r.surf.contour works well under the following circumstances: 1) the
contour lines extend to the the edge of the current region, 2) the
program is run at the same resolution as that of the input map, 3) there
are no disjointed contour lines, and 4) no spot elevation data BETWEEN
contour lines exist. Spot elevations at the tops of hills and the
bottoms of depressions, on the other hand, improve the output greatly.
Violating these constraints will cause non-intuitive anomalies to appear
in the output map. Run r.slope.aspect on r.surf.contour results to
locate potential anomalies. 

The running of r.surf.contour is very sensitive to the resolution of
rasterized vector map. If multiple contour lines go through the same
raster, slight anomalies may occur. The speed of r.surf.contour is
dependent on how far "apart" the contour lines are from each other (as
measured in rasters). Since a flood fill algorithm is used, the
program's running time will grow exponentially with the distance between
contour lines. 

===================================================================

This will only help if your data does not conform to one or more of
these conditions.

I hope this at least gave you some ideas.

-- 
Sincerely,

Jazzman (a.k.a. Justin Hickey)  e-mail: jhickey at hpcc.nectec.or.th
High Performance Computing Center
National Electronics and Computer Technology Center (NECTEC)
Bangkok, Thailand
==================================================================
People who think they know everything are very irritating to those
of us who do.  ---Anonymous

Jazz and Trek Rule!!!
==================================================================