Hello all,
I'm trying to patch some vector maps in GRASS 5.3, but there are problems. the
maps are contours and spot heights in shape format. when I import then,
everything is OK, the contours have the right z-value, and so the points (in
vector format). the problem is when I try to patch them, and the final result
comes with completely different z-values. all labels are changed.
any ideas?
thanks in advance
Carlos
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Carlos Henrique Grohmann - Guano
Geologist M.Sc - PhD Student at IGc-USP - Brazil
Linux User #89721 - guano at usp dot br -
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Hello
On Wed, 22 Sep 2004, Carlos Henrique Grohmann wrote:
Hello all,
I'm trying to patch some vector maps in GRASS 5.3, but there are problems. the
maps are contours and spot heights in shape format. when I import then,
everything is OK, the contours have the right z-value, and so the points (in
vector format). the problem is when I try to patch them, and the final result
comes with completely different z-values. all labels are changed.
any ideas?
v.patch is a simple algorithm and assumes the attribute numbers correspond to the same category labels (I presume you have the z co-ordinates as category labels) in all the input maps. If they don't then the output will be mixed up.
If your z values are all integers greater than 0 then you can make the attribute number be the actual z value and don't have any category labels. You should be able to achieve this with careful use of the command-line parameters to v.in.shape I think.
If you have 0, negative or decimal values I suppose you could multiply them by something and add a bit on to make them positive integers, or make sure all your attribute numbers occupy different ranges in all the inputs maps or something (no idea how to do that). I've run into this problem lots of times and it is very awkward. I think I worked around it just by giving every line in each map a different attribute number. That is very inefficient though.
Paul