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: Friday Apr 04 01:21:13 2025

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