[GRASS-dev] upload cat values from lines to points

GRASS GRASS developer
1

Hi devs,

One can use v.what.vect to upload cat values (or attribute values from attribute table) of a polygon vector layer (query map) to attribute table of a point vector layer.

How can I do the same, but using as map to query a line vector layer instead of polygon layer?

Cheers,

Paulo

2

Le 23 novembre 2016 17:31:17 GMT+01:00, Paulo van Breugel <p.vanbreugel@gmail.com> a écrit :

Hi devs,

One can use v.what.vect to upload cat values (or attribute values from
attribute table) of a polygon vector layer (query map) to attribute
table of a point vector layer.

How can I do the same, but using as map to query a line vector layer
instead of polygon layer?

Unless you create your points from the lines, the probability that your points are precisely on your lines is extremely low (even when you create them from the lines I'm not sure precision issues won't play you tricks).

I would create small buffers around the lines with attribute transfer to the buffers (-t flag of v.buffer).

Moritz

Cheers,

Paulo

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3

Moritz Lennert wrote

Le 23 novembre 2016 17:31:17 GMT+01:00, Paulo van Breugel &lt;

p.vanbreugel@

&gt; a écrit :

Hi devs,

One can use v.what.vect to upload cat values (or attribute values from
attribute table) of a polygon vector layer (query map) to attribute
table of a point vector layer.

How can I do the same, but using as map to query a line vector layer
instead of polygon layer?

Unless you create your points from the lines, the probability that your
points are precisely on your lines is extremely low (even when you create
them from the lines I'm not sure precision issues won't play you tricks).

I would create small buffers around the lines with attribute transfer to
the buffers (-t flag of v.buffer).

v.distance with a very low dmax?

-----
best regards
Helmut
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4

On 23-11-16 17:58, Helmut Kudrnovsky wrote:

Moritz Lennert wrote

Le 23 novembre 2016 17:31:17 GMT+01:00, Paulo van Breugel &lt;
p.vanbreugel@
&gt; a écrit :

Hi devs,

One can use v.what.vect to upload cat values (or attribute values from
attribute table) of a polygon vector layer (query map) to attribute
table of a point vector layer.

How can I do the same, but using as map to query a line vector layer
instead of polygon layer?

Unless you create your points from the lines, the probability that your
points are precisely on your lines is extremely low (even when you create
them from the lines I'm not sure precision issues won't play you tricks).

I would create small buffers around the lines with attribute transfer to
the buffers (-t flag of v.buffer).

These are points created with v.transects (using type=point and dleft and dright = 0) , so they should be exactly on the line. Probably v.distance is easier, will see what is faster.

v.distance with a very low dmax?

This sounds like the easiest solution, I'll try it out. Btw, Helmut, I'm looking into v.fixed.segmentpoints for multiple lines, but wanted to explore the alternative of using v.transects to create the points and then upload the line values to the points might be an alternative solution.

-----
best regards
Helmut
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