v.centerline fails with real data

[martinl]

I tried v.centerline to produce center line for highways in CZ imported from OSM, see (1), EPSG:5514 (you can use also 2065 if you have Proj.4 <4.9).

v.centerline input=highway out=highway_c

The result is one small line (red color) located somewhere in the space, see attachment:v-center-line.png​.

(1) ​http://geo102.fsv.cvut.cz/~landa/trac_attachments/highway.pack

[martinl]

result (red)

[mlennert]

v.centerline is meant for bundles of lines that have more of less the same trajectory and for which you want to define one "mean" line. As shown in the examples in the man page this could be two lines representing the riverbanks, or more lines representing the variance of trajectories along a more or less similar direction, such as lines of flight of airplanes above a specific area.

I don't really know what the "centerline" should be in your case ?

I added a few words to the man page to hopefully make this more explicit. If you think the module should do something else, than please go ahead and modify it. I'm leaving the ticket open for now, but at this stage, this is a "wontfix" or even a "worksforme" in my eyes.

[martinl]

Replying to mlennert:

v.centerline is meant for bundles of lines that have more of less the same trajectory and for which you want to define one "mean" line. As shown in the examples in the man page this could be two lines representing the riverbanks, or more lines representing the variance of trajectories along a more or less similar direction, such as lines of flight of airplanes above a specific area.

it seems to me that this also that case, there are two traffic lines for each highway.

I don't really know what the "centerline" should be in your case ?

A line between two traffic lines.

[mlennert]

Replying to martinl:

Replying to mlennert:

v.centerline is meant for bundles of lines that have more of less the same trajectory and for which you want to define one "mean" line. As shown in the examples in the man page this could be two lines representing the riverbanks, or more lines representing the variance of trajectories along a more or less similar direction, such as lines of flight of airplanes above a specific area.

it seems to me that this also that case, there are two traffic lines for each highway.

I don't really know what the "centerline" should be in your case ?

A line between two traffic lines.

After importing and zooming I can see what you mean. In order to get the centerlines of each of the highway pieces, you would have to iterate through them and apply v.centerline to each of them as v.centerline in its current state takes all lines in the map at once.

Moritz