## DESCRIPTION

v.build builds support files for GRASS vector maps. These support files supply topology and category information including spatial index that are needed by other GRASS modules.

GRASS is generating these support files automatically, only in rare cases the user has to (re)build them.

Refer to vector data processing in GRASS GIS for more information on GRASS vector data model.

## NOTES

v.build creates support files only for vector maps located in the user's current mapset. It's not possible to rebuild support files (option=build) for vector maps from other mapsets.

In case of errors, the user can optionally generate an error vector map containing the erroneous vectors for later inspection.

If error vector map is specified, v.build checks:

- isolated bondaries (which are not forming any areas),
- centroids outside of area,
- duplicated centroids.

Extensive checks for topological errors (flag -e) also includes:

- lines or boundaries of zero length,
- intersecting boundaries, ie. overlapping areas,
- areas without centroids that are not isles.

## EXAMPLES

### Build topology

Note that option=build recreates also spatial and category indices, not only topology. For linked OGR layers (see v.external) also feature index is created.

    v.build map=urbanarea option=build

Note that the vector map urbanarea must be located in the current mapset.

### Dump topology or indices

Dump options print topology, spatial, category or feature index to standard output. Such information can be printed also for vector maps from other mapsets. A description of the vector topology is available in the GRASS GIS 8 Programmer's Manual, section "Vector library topology management".

    v.build map=urbanarea option=dump

## SEE ALSO

v.build.all, v.build.polylines, v.edit, v.split

See also wxGUI vector digitizer.

## AUTHORS

Dave Gerdes, U.S.Army Construction Engineering Research Laboratory,
Michael Higgins, U.S.Army Construction Engineering Research Laboratory,
Radim Blazek, ITC-irst, Trento, Italy