.TH r.support
.SH NAME
\fIr.support\fR \- Allows the user to create and/or modify raster map layer
support files.
.br
.I (GRASS Raster Program)
.SH SYNOPSIS
.B r.support
.SH DESCRIPTION
The GRASS program \fIr.support\fR
allows the user to create and/or modify raster map layer support files.
It may be run only on raster map layers in the user's current mapset.
.LP
No non-interactive version of this program currently exists;
the user runs the program by typing \fBr.support\fR, and will be
queried for inputs.
.LP
Various GRASS programs depend on one or more of the following
GRASS \fIsupport\fR files:
.IP \fBcellhd\fR 10
The cell header file contains information on a map's projection, zone,
regional boundaries, row and column totals, cell resolution, storage format,
and compression.
It describes where and how this map's raster (cell) data fits in with reference
to other raster map layers' data.
Without it, the raster map layer could not be displayed or analyzed properly.
Using \fIr.support\fR, the user can change the # of columns, # of bytes per cell,
and default geographic region settings.
Generally, users would not change this information.
Cell header files are stored under the \fIcellhd\fR directory under
the user's current mapset.
.IP \fBstats\fR 10
Raster map layer statistics are saved in the form of a histogram and
range of the category values which occur in the map layer.
Statistics files are stored in subdirectories of the
\fIcell_misc\fR directory under the user's current mapset.
.IP \fBcats\fR 10
A category file associates each category value in the raster map layer
with a category description (label).
The user may add or edit the category descriptions,
alter the number of categories, and add or alter the map's title.
Category files associated with raster map layers are stored under the
\fIcats\fR directory in the user's current mapset.
.IP \fBcolr\fR 10
A color file associates each category value in the raster map layer with a color.
Using \fIr.support\fR, the user may assign one of eight color table types
to the raster map layer.
Map color table files are stored under the \fIcolr\fR and \fIcolr2\fR directories
under the user's current mapset.
.IP \fBhist\fR 10
Historical information about the raster map layer is stored in a history file.
The user may add or edit the raster map's title, data type, data source, data
description, and include comments.
(Note that the specification of map data type here is somewhat archaic,
and should always be set to \fIraster\fR.)
Map history files are stored under the \fIhist\fR directory under
the user's current mapset.
.SH NOTES
The \fIr.support\fR program attempts to verify that the information
in the cell header is reasonable.  The data format specified in the header
is verified against the raster map layer itself.  This includes checking
that files which the header indicates are \fIcompressed\fR are really
compressed, and that the number of rows and columns specified
in the header correspond to the actual file size.

The \fIr.support\fR program can also be used to determine the number
of columns and rows of data in a raster map layer,
in the event that no cell header is available.
This is useful, for example, for importing raster map layers created by software
other than GRASS.

If the file is not compressed, the file size should be the product of the
number of rows and columns.
If the file is compressed, this test cannot be performed since the
file size will bear no relation to the product.  The number
of rows can still be verified, but the number of columns cannot.
.LP
To compute or correct the \fIstats\fR, the cell header must be correct,
since the raster map layer is read to determine the stats.
.LP
If a new \fIcats\fR or \fIcolr\fR (or \fIcolr2\fR) file is required, the 
\fIstats\fR must be correct.
.LP
The user is allowed to change the number of categories
specified in the category file.  This should \fBonly\fR be done if the
user knows that the maximum category value in the raster map layer
is different than that which is recorded in the category file.
Changing the category value in the \fIcats\fR file allows the user to add more
category labels, or to remove labels.  It does NOT change the category
values in the raster map layer itself.

The color file is unique among GRASS support files.
While it is necessary to protect a user's original data from being modified
by users working under other mapsets,
these users need to be able to create color tables for maps that are stored
under mapsets other than their own.
Color table files meet both these objectives.
.LP
Color table files get stored in one of two directories, both under the user's
current mapset.  The color files created by a user for raster maps stored under
that user's current mapset get stored in the directory \fI$LOCATION/colr\fR
and cannot be modified or removed by other users.
The color table files that the user modifies/creates
for raster map layers \fInot\fR stored under the user's current mapset
get stored in a \fIsecondary color\fR file under the user's mapset.
This secondary color table is stored under \fI$LOCATION/colr2/<mapset>\fR
where <mapset> is the name of the mapset under which the raster map data
are stored.
In versions of GRASS prior to 3.0, this was also the case for
color tables in the user's own mapset.  Now, however, if a user modifies
a color table associated with a raster map layer in his own current mapset,
these changes will be made to the user's original color file
(i.e., the user's color changes will overwrite whatever previous color table file
existed for this map under the user's \fI$LOCATION/colr\fR directory).
No secondary color files are created for raster map layers stored in the user's
own mapset.
.SH WARNING
In order to modify the \fIcell header\fR,
the raster (cell) map layer under consideration must \fInot\fR be a
.I reclass
file.  This is because the \fIreclass\fR file's header does not
contain positional information,
but rather a reference to another raster map layer.  Thus it shares
a cell header with the referenced raster map layer.
In order to change the cell header, \fIr.support\fR must be run on the
true raster file referenced.
.SH "SEE ALSO"
For more information regarding the location and function of GRASS
support files, consult the 
.B GRASS Programmer's Manual
chapter on "GRASS Database Structure"
.LP
.I d.colors,
.I r.colors,
.I r.reclass
.SH AUTHOR
Michael Shapiro, U.S. Army Construction Engineering Research Laboratory