Re: [GRASS-user] v.dissolve for lines?
On 11/05/2010 09:59 PM, Bryan Keith wrote: On 10/19/2010 11:17 PM, Bryan Keith wrote: Hello, I have a vector line file that has lots of two-vertex lines. Many of these two-vertex lines share endpoints and really just make parts of one longer line. I'd like to dissolve these lines into one line when they have the same end point. It looks like v.dissolve only works for areas. Is there somewhere else I should be looking? Thank you. Did you have a look at v.build.polylines ? Additional note: line vectors have a direction. Two line segments with an equivalent node (end point) will *not* connect if they are in opposite directions. In this case you can try the v.edit tool=flip option (on those segments only) Thank you for the response. I finally got around to looking at this today. I made a simple example and tested with v.build.polylines, and it works great. Thank you. However, it turns out that I have many duplicate lines in my dataset. I created a simple example where there are duplicate lines, and v.build.polylines doesn't work in that case. What do I need to look at to get rid of duplicate lines? v.clean tool=rmdupl Might do it if the lines exactly overlap. Yes, that worked in my case. Thanks so much, Micha! Bryan ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] v.dissolve for lines?
On 10/19/2010 11:17 PM, Bryan Keith wrote: Hello, I have a vector line file that has lots of two-vertex lines. Many of these two-vertex lines share endpoints and really just make parts of one longer line. I'd like to dissolve these lines into one line when they have the same end point. It looks like v.dissolve only works for areas. Is there somewhere else I should be looking? Thank you. Did you have a look at v.build.polylines ? Additional note: line vectors have a direction. Two line segments with an equivalent node (end point) will *not* connect if they are in opposite directions. In this case you can try the v.edit tool=flip option (on those segments only) Thank you for the response. I finally got around to looking at this today. I made a simple example and tested with v.build.polylines, and it works great. Thank you. However, it turns out that I have many duplicate lines in my dataset. I created a simple example where there are duplicate lines, and v.build.polylines doesn't work in that case. What do I need to look at to get rid of duplicate lines? Bryan _ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user This mail was received via Mail-SeCure System. -- Micha Silver Arava Development Co. +972-52-3665918 http://www.surfaces.co.il ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] v.dissolve for lines?
On 11/05/2010 09:59 PM, Bryan Keith wrote: On 10/19/2010 11:17 PM, Bryan Keith wrote: Hello, I have a vector line file that has lots of two-vertex lines. Many of these two-vertex lines share endpoints and really just make parts of one longer line. I'd like to dissolve these lines into one line when they have the same end point. It looks like v.dissolve only works for areas. Is there somewhere else I should be looking? Thank you. Did you have a look at v.build.polylines ? Additional note: line vectors have a direction. Two line segments with an equivalent node (end point) will *not* connect if they are in opposite directions. In this case you can try the v.edit tool=flip option (on those segments only) Thank you for the response. I finally got around to looking at this today. I made a simple example and tested with v.build.polylines, and it works great. Thank you. However, it turns out that I have many duplicate lines in my dataset. I created a simple example where there are duplicate lines, and v.build.polylines doesn't work in that case. What do I need to look at to get rid of duplicate lines? v.clean tool=rmdupl Might do it if the lines exactly overlap. Bryan ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] v.dissolve for lines?
Micha Silver wrote: Bryan Keith wrote: Hello, I have a vector line file that has lots of two-vertex lines. Many of these two-vertex lines share endpoints and really just make parts of one longer line. I'd like to dissolve these lines into one line when they have the same end point. It looks like v.dissolve only works for areas. Is there somewhere else I should be looking? Thank you. Did you have a look at v.build.polylines ? Additional note: line vectors have a direction. Two line segments with an equivalent node (end point) will *not* connect if they are in opposite directions. Each line has two nodes, one at the start and one at the end. If at the end of one line any other line is starting or ending, this other line is added to the first line, reversing the direction if necessary. IOW, two lines with a common node will indeed connect, and the direction of one line may need to be reversed (done automatically). Very simple to test by digitizing a simple test vector. In this case you can try the v.edit tool=flip option (on those segments only) Should not be needed as pre-processing step for v.build.polylines. Markus M ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] v.dissolve for lines?
On 20/10/2010 08:36, Markus Metz wrote: Micha Silver wrote: Bryan Keith wrote: Hello, I have a vector line file that has lots of two-vertex lines. Many of these two-vertex lines share endpoints and really just make parts of one longer line. I'd like to dissolve these lines into one line when they have the same end point. It looks like v.dissolve only works for areas. Is there somewhere else I should be looking? Thank you. Did you have a look at v.build.polylines ? Additional note: line vectors have a direction. Two line segments with an equivalent node (end point) will *not* connect if they are in opposite directions. Each line has two nodes, one at the start and one at the end. If at the end of one line any other line is starting or ending, this other line is added to the first line, reversing the direction if necessary. IOW, two lines with a common node will indeed connect, and the direction of one line may need to be reversed (done automatically). Very simple to test by digitizing a simple test vector. Heh, thanks for the correction! Was this always the case? I seem to remember not be able to merge lines unless they were connected in the same direction. How does the line reversal work? That is, Which of the two line segments is chosen be get reversed? Regards, Micha In this case you can try the v.edit tool=flip option (on those segments only) Should not be needed as pre-processing step for v.build.polylines. Markus M This mail was received via Mail-SeCure System. -- Micha Silver http://www.surfaces.co.il/ Arava Development Co. +972-52-3665918 ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] v.dissolve for lines?
If You have lines with wrong direction or segment order, You can try to run my v.reorder_line_segments tool.[1] It will try to reorder same CAT line segments to be in increasing order. It also reverses line segments to be in order from start to end. It will work only for simple, stright lines and will go nuts on circular featrues etc, still sometimes it's faster than doing manual work. Current version will stop if line contains crossection, still that check can be removed. I introduced it only because module entered an endless loop if multiline looped back to itself. Code is unfinished, as I was not able to figure out how to solve non-trivial cases and thus cleaned my data by hand. It's tested on GRASS 7. It requires ctypes. If You need aditional help, drop a note. Maris. 1. http://www.gisnet.lv/trac/gisnet/browser/gisnettools/v.reorder_line_segments.py 2010/10/20, Micha Silver mi...@arava.co.il: On 20/10/2010 08:36, Markus Metz wrote: Micha Silver wrote: Bryan Keith wrote: Hello, I have a vector line file that has lots of two-vertex lines. Many of these two-vertex lines share endpoints and really just make parts of one longer line. I'd like to dissolve these lines into one line when they have the same end point. It looks like v.dissolve only works for areas. Is there somewhere else I should be looking? Thank you. Did you have a look at v.build.polylines ? Additional note: line vectors have a direction. Two line segments with an equivalent node (end point) will *not* connect if they are in opposite directions. Each line has two nodes, one at the start and one at the end. If at the end of one line any other line is starting or ending, this other line is added to the first line, reversing the direction if necessary. IOW, two lines with a common node will indeed connect, and the direction of one line may need to be reversed (done automatically). Very simple to test by digitizing a simple test vector. Heh, thanks for the correction! Was this always the case? I seem to remember not be able to merge lines unless they were connected in the same direction. How does the line reversal work? That is, Which of the two line segments is chosen be get reversed? Regards, Micha In this case you can try the v.edit tool=flip option (on those segments only) Should not be needed as pre-processing step for v.build.polylines. Markus M This mail was received via Mail-SeCure System. -- Micha Silver http://www.surfaces.co.il/ Arava Development Co. +972-52-3665918 ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] v.dissolve for lines?
Micha Silver wrote: On 20/10/2010 08:36, Markus Metz wrote: Micha Silver wrote: Bryan Keith wrote: Hello, I have a vector line file that has lots of two-vertex lines. Many of these two-vertex lines share endpoints and really just make parts of one longer line. I'd like to dissolve these lines into one line when they have the same end point. It looks like v.dissolve only works for areas. Is there somewhere else I should be looking? Thank you. Did you have a look at v.build.polylines ? Additional note: line vectors have a direction. Two line segments with an equivalent node (end point) will *not* connect if they are in opposite directions. Each line has two nodes, one at the start and one at the end. If at the end of one line any other line is starting or ending, this other line is added to the first line, reversing the direction if necessary. IOW, two lines with a common node will indeed connect, and the direction of one line may need to be reversed (done automatically). Very simple to test by digitizing a simple test vector. Heh, thanks for the correction! Was this always the case? I seem to remember not be able to merge lines unless they were connected in the same direction. How does the line reversal work? That is, Which of the two line segments is chosen be get reversed? v.build.polyline works as follows: it picks a line and from its start node, walks back as long as exactly one other line is connected to this node. Line directions are reversed as required, i.e. it does not matter if the next line is connected to the current node by its start or end node. Once the start line of a polyline is identified, it walks forward and adds all vertices (in reverse order if needed) of connected lines to the start line, i.e. the start line and connecting lines are reversed as needed. That is, if a line is reversed depends on what node is initially picked for building polylines. If the direction of lines is important (it's not for boundaries to build areas), you have to manually change line directions with either v.edit or the wxdigitizer or the tool by Maris. Markus M Regards, Micha In this case you can try the v.edit tool=flip option (on those segments only) Should not be needed as pre-processing step for v.build.polylines. Markus M This mail was received via Mail-SeCure System. -- Micha Silver http://www.surfaces.co.il/ Arava Development Co. +972-52-3665918 ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
[GRASS-user] v.dissolve for lines?
Hello, I have a vector line file that has lots of two-vertex lines. Many of these two-vertex lines share endpoints and really just make parts of one longer line. I'd like to dissolve these lines into one line when they have the same end point. It looks like v.dissolve only works for areas. Is there somewhere else I should be looking? Thank you. Bryan ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] v.dissolve for lines?
On 10/19/2010 11:17 PM, Bryan Keith wrote: Hello, I have a vector line file that has lots of two-vertex lines. Many of these two-vertex lines share endpoints and really just make parts of one longer line. I'd like to dissolve these lines into one line when they have the same end point. It looks like v.dissolve only works for areas. Is there somewhere else I should be looking? Thank you. Did you have a look at v.build.polylines ? Additional note: line vectors have a direction. Two line segments with an equivalent node (end point) will *not* connect if they are in opposite directions. In this case you can try the v.edit tool=flip option (on those segments only) Bryan ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user This mail was received via Mail-SeCure System. -- Micha Silver Arava Development Co. +972-52-3665918 http://www.surfaces.co.il ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
