Hi Ivan, hi folks, On Sun, Nov 04, 2007 at 03:25:17PM +0100, ivan marchesini wrote: > [...] > this to explain the results of v.build... thanks a lot for your detailed explanation.
> but this doesn't explain the reason of the strange overlay... I suspect, v.overlay using operator "AND" is buggy. I found a bug report (ID #5427) describing this behavior, which has still open status. Using operator "NOT", v.overlay will work properly. In my case that solves the issue. > why did you try to do all the intersection line for line... > why didn't you create a single "lines map" that contain all the > latitudes and then perform the overlay? Well, I'm new to GRASS and I did it this way, because don't know to do better this time - I'll work on it ;) My task is the following: I would like to figure out for every single latitude, how much of it is covered by ocean surface and how much is covered by a continent. So, I want a table like this Lat|Ocean length (meters)|total length (meters) [...] 10N|???|39470.171 [...] Total length I calculated using a perl script. To get the "Ocean Length", I export the vector maps with the intersections (using points), afterwards I use another perl script, to calc length of the segments and finally the sum of all segments. That's why I didn't use a single "lines map" - just to keep things clearly arranged. My next excercise will be connection those segments lengths to the GRASS database. Regards, Martin _______________________________________________ grassuser mailing list grassuser@grass.itc.it http://grass.itc.it/mailman/listinfo/grassuser