v.support - Creates GRASS support files for
(binary) GRASS vector data.
(GRASS Vector Program)
v.support builds GRASS support files for (binary)
GRASS vector data files. These support files supply
topology (dig_plus) and category
(dig_att) information that are needed by other
(e.g., by v.digit,
The program gives the user the options of:
- building topological information (the
dig_plus file) needed by
the vector data file, and/or
- editing the category label (dig_cats) file
associated with the vector data file.
Program parameters and flags have the following meanings.
- Snap nodes. Valid only with build option.
- Prompt user for threshold value. Valid only with
build option. This flag is designed to be used
only by the
program, and can usually be ignore.
- Reset corners of map region from range of data values.
The user can run this program non-interactively by
specifying parameter values (and optionally, flag settings)
on the command line.
- Name of binary GRASS vector data file for which support
files are to be created or modified. This map layer must
exist in the user's current GRASS mapset.
- Build topology information (dig_plus file),
or edit categories (dig_att file) for
Options: build, edit
- Snapping threshold value to be used when building
topology. Specified value is always saved in file header.
(Note: snapping is done only
with build option and -s flag).
- Name of new vector binary file, where are saved all area edges with topology
problems like free ends or not closed areas.
Alternately, the user can simply type the command
v.support on the command line. In this event, the
program will prompt the user to enter parameter values and
If the build option is chosen, the user may
further specify the -s flag, to snap nodes in the
vector file. If nodes are to be snapped, the user can
either: (1) use the calculated default threshold (based on
the scale of vector data); (2) enter the -p flag, causing
the program to prompt the user for a snapping threshold
value; or (3) enter a specific threshold value on the
The spatial assignment of category values (found in the
dig_att file) is also performed during building of
The edit option allows the user to edit the
category labels to be associated with the category values
attached to the vector data during topology building.
These labels, if created, are then used for raster map
layers derived from their vector counterparts. The labels
are placed in the dig_cats directory.
A dig_plus file must be created for each imported vector map
before it can be used in post-GRASS 3.0 versions of digit
(now referred to as v.digit).
Topological information for GRASS vector files can also be built using
option 4 of the
This program will convert pre-4.0 version GRASS vector files to 4.0 format.
v.support creates support files only for binary
vector files located in the user's current mapset.
Dave Gerdes, U.S.Army Construction Engineering
U.S.Army Construction Engineering
Last changed: $Date: 2002/08/26 08:48:36 $