Hi Hamish, Thank you for the suggestions. v.hull is something that i had passed over before, it wont work on this occasion as the dam is boomerang shaped, but i will be sure to use it when i can. Takes a fair deal of processing out.
For those that are interested the final result was as follows: v.category option=add cat=1 step=0 type=area (this filled in my islands - as they weren't islands, just obsticales) v.extract type=area new=1 list=1-99999 v.dissolve Thanks, Ed 2008/5/29 Hamish <[EMAIL PROTECTED]>: > Edward Tomlinson: > > I have a whole bunch of data from an RTK GPS. File exists > > as a MapInfo file. > > Imports into grass fine with area and centroids. > > > > My problem is however, i want to create another vector file > > that contains the mask or the external (an internal island) boundary. > > > > I have been able to create the external boundary fine > > through the following. > > v.category (delete categories) > > v.category (add category as 1 for all) > > v.dissolve (combine all boundaries with common category) > > > > This is great and works fine for the external boundary. > > However there is meant to be an island in there. Somewhere > > along the way (i think after the second call to v.category) > > it fills that island in. > > right. > > > Has anyone got any hints or ideas? > > > > Essentially i am trying to create this vector to generate a > > mask for further interpolation of the point heights. I am > > assuming that i need this island removed (as there is no > > point data for it) otherwise it is going to effect > > the interpolation. > > Use v.overlay for the new and original map, operator=not, etc. > or other combination of operator=and etc until you get what you want. > > another trick is "v.extract list=1-99999999" to only extract features with > a cat number. (then v.overlay) > > v.hull is another module to look at for this instead of v.dissolve. > > > Hamish > > > > > >
_______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
