[GRASS-dev] selecting lines boundary-wise

GRASS GRASS developer
1

Hi list,

I'm trying to export the boundaries of a vector file, but would like
to avoid duplication of common boundaries. It's easy to know which
boundaries limit a given area, but how can I extract only one
boundary. For example, area 1 has boundaries 6,7,9 while for area 2
these are 8,9. Is there a way to extract the lines of boundary 8 only
for area 2 in order to avoid duplicating it? A comination of
Vect_get_area_boundaries(&Map,area,List) with something else?

Thanks,
Jaime

2

Jaime Carrera wrote:

I'm trying to export the boundaries of a vector file, but would like
to avoid duplication of common boundaries. It's easy to know which
boundaries limit a given area, but how can I extract only one
boundary. For example, area 1 has boundaries 6,7,9 while for area 2
these are 8,9. Is there a way to extract the lines of boundary 8 only
for area 2 in order to avoid duplicating it? A comination of
Vect_get_area_boundaries(&Map,area,List) with something else?

A combination of v.dissolve + v.overlay?

note that grass only keeps a single boundary line between two areas, it
doesn't duplicate them, 1 for each area. see 'v.clean tool=rmdupl'
(well it can handle input data like that but complains that the data is
topologically unclean)

Hamish

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