NAME

       v.patch  - Create a new vector map layer by combining other vector map layers.

KEYWORDS

       vector, geometry

SYNOPSIS

       v.patch
       v.patch help
       v.patch  [-ae] input=name[,name,...] output=name  [bbox=name]   [--overwrite]  [--verbose]
       [--quiet]

   Flags:
       -a
           Append files to existing file (overwriting existing files must be activated)

       -e
           Copy also attribute table
           Only the table of layer 1 is currently supported

       --overwrite
           Allow output files to overwrite existing files

       --verbose
           Verbose module output

       --quiet
           Quiet module output

   Parameters:
       input=name[,name,...]
           Name of input vector map(s)

       output=name
           Name for output vector map

       bbox=name
           Name for output vector map where bounding boxes of input vector maps are written to

DESCRIPTION

       v.patch allows the user to combine any number  of  vector  maps  together  to  create  one
       composite vector map. If the table structures are identical, attributes are transferred to
       the new table.

NOTES

       Any vectors that are duplicated among the maps being patched together (e.g., border lines)
       will  have  to  be  edited  or  removed  after  v.patch  is  run. Such editing can be done
       automatically using v.clean.

       Lines may need to be snapped with v.clean tool=snap,break,rmdupl.

       Boundaries may need to be cleaned with v.clean tool=break,rmdupl,rmsa repeatedly until the
       rmsa  tool  (Remove  small  angles  at nodes) no longer modifies any boundaries. If vector
       topology is still not  clean,  boundaries  may  also  need  to  be  snapped  with  v.clean
       tool=snap,break,rmdupl.

       When  using the -a flag, the user has to make sure that the features in the different maps
       added to the output map  do  not  have  overlapping  category  numbers,  unless  identical
       category  numbers reflect identical attributes, otherwise the attributes of the added maps
       are lost. To avoid this, the user can use v.category option=sum to change category  values
       of some of the maps before patching.

EXAMPLES

       Patch together two maps with mixed feature types:
          v.patch input=geology,streams out=geol_streams

       Append one map to another:
          g.copy vect=roads,transport
          v.patch -a input=railroads output=transport --overwrite

SEE ALSO

       v.clean, v.build, v.select, v.overlay

AUTHORS

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

       Last changed: $Date: 2011-11-08 03:29:50 -0800 (Tue, 08 Nov 2011) $

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