NAME

       v.proj  - Re-projects a vector map from one location to the current location.

KEYWORDS

       vector, projection, transformation, import

SYNOPSIS

       v.proj
       v.proj --help
       v.proj  [-lzwb] location=name  [mapset=name]   [input=name]   [dbase=path]   [smax=float]   [output=name]
       [pipeline=string]   [--overwrite]  [--help]  [--verbose]  [--quiet]  [--ui]

   Flags:
       -l
           List vector maps in input mapset and exit

       -z
           Assume z coordinate is ellipsoidal height and transform if possible
           3D vector maps only

       -w
           Disable wrapping to -180,180 for latlon output
           Latlon output only, default is -180,180

       -b
           Do not build vector topology
           Recommended for massive point projection

       --overwrite
           Allow output files to overwrite existing files

       --help
           Print usage summary

       --verbose
           Verbose module output

       --quiet
           Quiet module output

       --ui
           Force launching GUI dialog

   Parameters:
       location=name [required]
           Location containing input vector map
           Location name (not location path)

       mapset=name
           Mapset containing input vector map
           Default: name of current mapset

       input=name
           Name of input vector map to re-project

       dbase=path
           Path to GRASS database of input location
           Default: path to the current GRASS GIS database

       smax=float
           Maximum segment length in meters in output vector map
           Increases accuracy of reprojected shapes, disable with smax=0
           Default: 10000

       output=name
           Name for output vector map (default: input)

       pipeline=string
           PROJ pipeline for coordinate transformation

DESCRIPTION

       v.proj allows a user to convert a vector map in a specified mapset of  a  specified  location  (different
       from current) with projection of input location to the vector map in a current mapset of current location
       with projection of current location (both projections are defined by corresponding PROJ_INFO files).  The
       projection information is taken from the current PROJ_INFO files, as set and viewed with g.proj.

NOTES

       If output is not specified it is set to be the same as input map name.
       If mapset is not specified, its name is assumed to be the same as the current mapset’s name.
       If dbase is not specified it is assumed to be the current database. The user only has to specify dbase if
       the source location is stored in another separate GRASS database.
       If smax is set to 0 the automated vertex densification is disabled (not recommended).

       v.proj supports general datum transformations, making use of the PROJ.4  co-ordinate  system  translation
       library.

       When projecting into a latlon location, east coordinates are wrapped by the proj4 library to fit into the
       range -180,180. This is in most cases appropriate, but can cause errors  the  input  vector  crosses  the
       datum line at 180E/W. In this case wrapping of east coordinates to -180,180 needs to be disabled with the
       -w flag.

       When reprojecting massive point clouds for which topology is not necessary, the user can set the -b  flag
       to suppress the building of topology of the output map.

       In  order  to preserve spatial detail, v.proj performs automated vertex densification (as an alternative,
       v.split could be used before reprojecting. Without vertex densification,  depending  on  the  source  and
       target CRS (Coordinate Reference System), geometries can be substantially deformed (straight lines become
       curves, squares become trapezoids,  etc).  The  densification  of  linear  features  can  help  to  avoid
       topological errors.

EXAMPLES

       v.proj in=mymap location=latlong mapset=user1

REFERENCES

       1      Evenden,  G.I.   (1990)  Cartographic  projection  procedures  for the UNIX environment - a user’s
              manual.  USGS Open-File Report 90-284 (OF90-284.pdf)  See  also  there:  Interim  Report  and  2nd
              Interim Report on Release 4, Evenden 1994).

       2      Richards,  John  A.  (1993),  Remote  Sensing Digital Image Analysis, Springer-Verlag, Berlin, 2nd
              edition.

       PROJ 4: Projection/datum support library.

       Further reading

           •   ASPRS Grids and Datum

           •   Projections Transform List (PROJ.4)

           •   MapRef - The Collection of Map Projections and Reference Systems for Europe

           •   Information and Service System for European Coordinate Reference Systems - CRS

           •   Cartographical Map Projections by Carlos A. Furuti

SEE ALSO

        g.proj, m.proj, r.proj, i.rectify, r.stats, v.sample, v.split, v.surf.idw, v.surf.rst

AUTHORS

       Irina Kosinovsky, US ARMY CERL
       M.L. Holko, USDA, SCS, NHQ-CGIS
       R.L. Glenn, USDA, SCS, NHQ-CGIS

SOURCE CODE

       Available at: v.proj source code (history)

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       © 2003-2019 GRASS Development Team, GRASS GIS 7.8.2 Reference Manual