[GRASS-user] multiple

[Stefan Blumentrath]

Hi Frank,

Yes, you are right. To get the intersection point you patch the line maps (v.patch), use v.clean on the patched maps and sve the intersection points (errors option in v.clean). Then you add categories to the generated points with v.category...
That just for correction of my earlier suggestion. Your approach with v.profile seems way more appropriate.

If all your lines have the same cat value, you could create new, induvial cat values with v.category, before you run v.profile (I have not looked at your dataset yet...)?

Cheers
Stefan

From: Frank David <frank.david at geophom.fr>
Sent: onsdag 27. april 2022 19:23
To: Stefan Blumentrath <Stefan.Blumentrath at nina.no>; GRASS user list <grass-user at lists.osgeo.org>
Subject: Re: [GRASS-user] multiple


Hi Stephan,

I'm not very used to v.overlay, but it seems to be used with area and not with lines crossing lines, isn't it ?

Frank

Le 27/04/2022 à 09:14, Stefan Blumentrath a écrit :

Hi Frank,



My general approach would be like this:

v.overay to intersect transects and lines

v.to.points use=start to get transect start points

v.distance to get distance from transect start point to point where lines cross



With v.distance you need to try whether it is sufficient to compute distance to the nearest point only or if you need to compute distance to all intersection points within the distance equal to the length of the transect...

If the latter is the case you would need to filter out lines with distances that are not along a transect.



Hope that helps.

v.distance can produce lines, so you could check visually if the approach works as expected.



Just a suggestion.



Cheers

Stefan



-----Original Message-----

From: grass-user <grass-user-bounces at lists.osgeo.org><mailto:grass-user-bounces at lists.osgeo.org> On Behalf Of Frank David

Sent: tirsdag 26. april 2022 20:01

To: GRASS user list <grass-user at lists.osgeo.org><mailto:grass-user at lists.osgeo.org>

Subject: [GRASS-user] multiple



Hello,



I need to identify vector lines (like roads, rivers) crossed by a transect and get distance from the beginning of the transect. For the moment I'm using v.profile but it returns only the first item. Is there any way to get all crossed lines ?



Thank for your help,



Frank



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