NAME

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

KEYWORDS

       vector, projection, transformation, import

SYNOPSIS

       v.proj
       v.proj --help
       v.proj  [-lzwb]  project=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:
       project=name [required]
           Project (location) containing input vector map
           Project name (not path to project)

       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 project
           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 project (different from
       current) with coordinate reference system (CRS) of source project to the vector map in a  current  mapset
       of  current  project with CRS of current project (both CRSs are defined in their corresponding projects).
       The CRS information can be viewed and managed with g.proj.

       For an introduction to map CRSs (and the PROJ library), 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 project 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 project, 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 project (and mapset) into the current mapset:
       v.proj in=mymap project=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: Friday Apr 04 01:20:22 2025

       Main index | Vector index | Topics index | Keywords index | Graphical index | Full index

       © 2003-2025 GRASS Development Team, GRASS GIS 8.4.1 Reference Manual

GRASS 8.4.1                                                                                       v.proj(1grass)