table of contents
v.import(1grass) | GRASS GIS User's Manual | v.import(1grass) |
NAME¶
v.import - Imports vector data into a GRASS vector map using OGR library and reprojects on the fly.
KEYWORDS¶
vector, import, projection
SYNOPSIS¶
v.import
v.import --help
v.import [-flo] input=string
[layer=string[,string,...]] [output=name]
[extent=string] [encoding=string]
[snap=float] [epsg=integer]
[datum_trans=integer] [--overwrite] [--help]
[--verbose] [--quiet] [--ui]
Flags:¶
- -f
-
List supported OGR formats and exit - -l
-
List available OGR layers in data source and exit - -o
-
Override projection check (use current project’s CRS)
Assume that the dataset has the same coordinate reference system (CRS) as the current project - --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:¶
- input=string [required]
-
Name of OGR datasource to be imported - layer=string[,string,...]
-
OGR layer name. If not given, all available layers are imported - output=name
-
Name for output vector map (default: input) - extent=string
-
Output vector map extent
Options: input, region
Default: input
input: extent of input map
region: extent of current region - encoding=string
-
Encoding value for attribute data - snap=float
-
Snapping threshold for boundaries (map units)
A suitable threshold is estimated during import
Default: -1 - epsg=integer
-
EPSG projection code
Options: 1-1000000 - datum_trans=integer
-
Index number of datum transform parameters
-1 to list available datum transform parameters
Options: -1-100
DESCRIPTION¶
v.import imports vector data from files and database connections supported by the OGR library into the current project (previously called location) and mapset. If the coordinate reference system (CRS) of the input does not match the CRS of the project, the input is reprojected into the current project. In case that the CRS of the input map does match the CRS of the project, the input is imported directly.
Supported Vector Formats¶
v.import uses the OGR library which supports various vector data formats including ESRI Shapefile, Mapinfo File, UK .NTF, SDTS, TIGER, IHO S-57 (ENC), DGN, GML, GPX, AVCBin, REC, Memory, OGDI, and PostgreSQL, depending on the local OGR installation. For details see the OGR web site. The OGR (Simple Features Library) is part of the GDAL library, hence GDAL needs to be installed to use v.import.
The list of actually supported formats can be printed by -f flag.
NOTES¶
v.import checks the CRS metadata of the dataset to be
imported against that of the current project. If not identical a related
error message is shown.
To override this CRS check (i.e. to use current project’s CRS) by
assuming that the dataset has the same CRS as the current project the
-o flag can be used. This is also useful when geodata to be imported
do not contain any CRS metadata at all. The user must be sure that the CRS
is identical in order to avoid introducing data errors.
Topology cleaning¶
When importing polygons, non-topological polygons are converted to topological areas. If the input polygons contain errors (unexpected overlapping areas, small gaps between polygons, or warnings about being unable to calculate centroids), the import might need to be repeated using a snap value as suggested in the output messages. The default value of snap=-1 means that no snapping will be done.
The snap threshold defines the maximal distance from one to another vertex in map units (for latitude-longitude projects in degrees). If there is no other vertex within snap distance, no snapping will be done. Note that a too large value can severely damage area topology, beyond repair.
Post-processing: Snapped boundaries may need to be cleaned with v.clean, using its tools break,rmdupl,rmsa. For details, refer to the v.clean manual page.
EXAMPLE¶
# import SHAPE file at full extent and reproject to current project CRS v.import input=research_area.shp output=research_area extent=input
SEE ALSO¶
v.clean, v.in.lines, v.in.ogr, v.proj
AUTHORS¶
Markus Metz
Improvements: Martin Landa, Anna Petrasova
SOURCE CODE¶
Available at: v.import source code (history)
Accessed: Saturday Jul 27 17:09:13 2024
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GRASS 8.4.0 |