On 18/12/15 12:59, Lluís Vicens wrote:
Hi all,
I'm doing some basic exercises based on v.net on GRASS GIS but I'm
getting some unexpected results (according to my knowledge and my
understanding of the v.net manual). When I execute the following command:
v.net input=streets_clean points=libraries output=network
operation=connect threshold=50
I get unsatisfactory results according to the v.net manual: "While the
arcs created with v.net will retain any attribute information associated
with the input vector line/boundary file in data layer 1, nodes created
and stored in data layer 2 will not have any associated attribute
information."
The problem is that the new created lines connecting the points
(libraries) to the existing network (streets_clean) doesn't retain
neither show any kind of attributes.
They do not have any attributes as they are new lines. Cf the
explanation below
There is a new geometry with no
attributes associated. As far as I remember, older GRASS GIS versions
(6.4.x) worked well on this issue.
Older GRASS versions just assumed that these lines should have the same
category (identifier) as the first line touched, and so they were linked
to the same attributes at these lines. Now, v.net creates new categories
for these connecting lines which seems the more correct solution to me.
Any hints?
The easiest solution, and in my eyes this should be the default [1], is
to use the '-s' flag of v.net which snaps the points to the lines. In
cases where points are buildings and lines are roads this makes more
sense as dimensionless points are just an abstract representation of
buildings and you will not build a road from the existing streets
through the entry door of the building towards its center ;-)
Moritz
[1] https://trac.osgeo.org/grass/ticket/2780
My GRASS GIS version on gnu/linux:
/version=7.0.1//
//date=2015//
//revision=00000//
//build_date=2015-08-06//
//build_platform=x86_64-unknown-linux-gnu/
I've already tested a Windows version with the same results
/version=7.0.2
date=2015
revision=66861
build_date=2015-11-19
build_platform=i686-pc-mingw32
/
--
*Lluís Vicens*
Servei de Sistemes d'Informació Geogràfica
-
Universitat de Girona
*SIGTE*
-
Pl. Ferrater Mora 1
17071 Girona
Tel +34 972 418 039 (7025 intern)
[email protected] <mailto:[email protected]>
http://www.sigte.udg.edu
Twitter http://twitter.com/SIGTE_UDG
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