v.proj(1grass) GRASS GIS User's Manual v.proj(1grass)
NAME
v.proj - Re-projects a vector map from one location to the current lo-
cation.
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 corre-
sponding 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 an-
other 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 neces-
sary, 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 repro-
jecting. Without vertex densification, depending on the source and tar-
get 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 topologi-
cal 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 In-
terim 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, trans-
formations, pipeline operator)
• MapRef - The Collection of Map Projections and Reference Sys-
tems for Europe
• Information and Service System for European Coordinate Refer-
ence 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: unknown
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GRASS 7.8.7 v.proj(1grass)
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