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.

       For an introduction to map projections (with PROJ),see the manual page of r.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 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.

EXAMPLE

       Reprojection of a vector map from another location and mapset into the current mapset:
       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: Projection/datum support library.

       Further reading

           •   ASPRS Grids and Datum

           •   Projections Transform List (PROJ)

           •   Coordinate operations by PROJ (projections, conversions, transformations, pipeline
               operator)

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

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

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)

       Accessed: Mon Jun 13 15:10:21 2022

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       © 2003-2022 GRASS Development Team, GRASS GIS 8.2.0 Reference Manual