[GRASS-dev] change in vector area format?

[Markus Metz]

Michael Barton wrote:
> Maybe I just missed the announcement. But I was surprised to find that 
> areas no longer displayed as areas in GRASS 7, but only as boundaries. 
> After trying multiple vector area files and considerable futzing with 
> various settings I got an error that said that the topology was bad. 
> When I rebuilt topology I could again display areas.
>
> Does this rebuilding of vector areas under GRASS 7 have any negative 
> repercussions for displaying the same files in GRASS 6?
Up to now, grass7 vectors are fully compatible with grass6 vectors: 
grass6 can work with grass7 vectors. Not the other way around, because 
in grass7, the spatial index is again file-based, not built on the fly. 
Consequently, grass7 can open a grass6 vector only on level 1 (no topo) 
and areas are not available until topo has been rebuilt.

This change was submitted to trunk on July 13 2009 as r38385, see also 
[1]. The announcement is here [2].

We could change grass7 behaviour to built sidx on the fly if it is not 
available, but that defeats the purpose of the file-based spatial index. 
Just run v.what on a larger vector map once in grass6 and once in grass7 
after rebuilding topo, elev_lid792_bepts in nc_spm_08 is a good example. 
Your suggestions about additional functionality in v.what would also 
heavily profit from it (is on my todo list...).

Markus M

[1] https://trac.osgeo.org/grass/wiki/Grass7/VectorLib
[2] http://lists.osgeo.org/pipermail/grass-dev/2009-July/045098.html