The problem is maybe cause by the superposition of several points. So the
number of points you have is really important and you surelly can decrease
this number using your program or and ascii file. It's simple to do that
with MAPINFO, a GIS.

Regards

Michael Verreault, ing., M.Sc.A.
Hydrogéologue
Resp. Hydrogéologie et Environnement
Les Laboratoires SL inc.
1309, blv. St-Paul
Chicoutimi (QC) G7J 3Y2
Tel: 418-698-6827
Fax: 418-543-6812