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

Provided by: grass-doc_7.8.2-1build3_all

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

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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