DESCRIPTION converts a vector map in ASCII format to a vector map in binary format. The module may import two formats:

The v.out.ascii GRASS module performs the function of in reverse; i.e., it converts vector maps in binary format to ASCII format. These two companion programs are useful both for importing and exporting vector maps between GRASS and other software, and for transferring data between machines.


The input is read from the file specified by the input option or from standard input.

The field separator may be a character, the word 'tab' (or '\t') for tab, 'space' (or ' ') for a blank, or 'comma' (or ',') for a comma.

An attribute table is only created if it is needed, i.e. when at least one attribute column is present in the input file besides geometry columns. The attribute column will be auto-scanned for type, but may be explicitly declared along with the geometry columns using the columns parameter.

Latitude/Longitude data may be given in a number of ways. Decimal degrees must be positive or negative instead of using a hemisphere letter. Mixed coordinates must use a hemisphere letter. Whole minutes and seconds must always contain two digits (example: use 167:03:04.567; and not 167:3:4.567).

Acceptable formats:
key: D=Degrees; M=Minutes; S=Seconds; h=Hemisphere (N,S,E,W)

  • (+/-)DDD.DDDDD
  • DDDh
  • DDD:MMh
  • DDD:MM:SSh

    Use the -z flag to convert ASCII data into a 3D vector map.

    In special cases of data import, such as the import of large LIDAR datasets (millions of data points), it may be necessary to disable topology support (creating a GRASS vector level 1 vector map) due to memory constraints. This is done with the -b flag. As only very few vector modules support points data processing at vector level 1, usually topology is required (vector level 2). Therefore it is recommened that the user first try to import the data without creating a database (the -t flag) or within a subregion (the -r flag) before resorting the to disabling of topology.

    A GRASS ASCII vector map (in standard format mode) may contain a mix of primitives including points, lines, boundaries, centroids, areas, faces, and kernels. The GRASS ASCII vector format may contain a header with various metadata (see example below). The header is not required if the -n flag is used.

    The header is similar as the head file of vector binary format but contains bounding box also. Key words are:


    The body begins with the row:

    followed by records of primitives:
     X Y [Z]
     X Y [Z]
    Everything above in [ ] is optional.

    The primitive codes are as follows:

    The coordinates are listed following the initial line containing the primitive code, the total number of vectors in the series, and (optionally) the number of categories (1 for a single layer, higher for multiple layers). Below that 1 or several lines follow to indicate the layer number and the category number (ID).
    The order of coordinates is
      X Y [Z]
    In pre-GRASS 6 versions of the ASCII file, the order of coordinates is:
    Y X
    If old version is requested, the output files from v.out.ascii is placed in the $LOCATION/$MAPSET/dig_ascii/ and $LOCATION/$MAPSET/dig_att directory.

    Import of files without category ID column

    If the input file does not contain a vector ID column, there is the possibility to auto-generate these IDs (categories). To automatically add an additional column named 'cat', the cat parameter must be set to the virtual column number 0 (cat=0). This is the default action if the cat parameter is not set.

    Importing from a spreadsheet

    Data may be imported from many spreadsheet programs by saving the spreadsheet as a comma separated variable (.csv) text file, and then using the fs=',' option with in points mode. If the input file contains any header lines, such as column headings, the skip parameter should be used. These skipped header lines will be written to the map's history file for later reference (read with -h). The skip option only works in points mode.

    Any line starting with the hash character ('#') will be treated as a comment and skipped completely if located in the main data file. If located in the header, as defined by the skip parameter, it will be treated as a header line and written to the history file.

    Import of sexagesimal degree (degree, minutes, seconds, DMS)

    The import of DMS formatted degrees is supported (in this case no sign but N/S, E/W characters are used to indicate the hemispheres). While the positions are internally translated into decimal degrees during the import, the original DMS values are maintained in the attribute table. This requires both the latitude and the longitude columns to be defined as varchars(), not as numbers. A warning will be issued which can be ignored.

    Importing only selected columns

    Although doesn't have an option to specify which columns should be imported, you can use a shell filter to achieve the same effect, e.g.:
    # Print out the column number for each field, supposing the file has a header
    head -1 input_file | tr '<the_field_separator_character>' '\n' | cat -n
    # From the listing, select the columns you want and feed them to
    # do not use the input= option
    cut -d<the_field_separator_character> -f<comma-separated_list_of_columns> input_file | <your_options>


    Example 1a) - standard format mode

    Sample ASCII polygon vector map for 'standard' format mode. The two areas will be assigned categories 20 and 21. The example can be tested in the Spearfish sample dataset:

    echo "ORGANIZATION: GRASS Development Team
    DIGIT DATE:   1/9/2005
    DIGIT NAME:   -
    MAP NAME:     test
    MAP DATE:     2005
    MAP SCALE:    10000
    OTHER INFO:   Test polygons
    ZONE:  0
    MAP THRESH:   0.500000
    B  6
     5958812.48844435 3400828.84221011
     5958957.29887089 3400877.11235229
     5959021.65906046 3400930.7458436
     5959048.47580612 3400973.65263665
     5959069.92920264 3401032.64947709
     5958812.48844435 3400828.84221011
    C  1 1
     5958952.42189184 3400918.23126419
     1 20
    B  4
     5959010.9323622 3401338.36037757
     5959096.7459483 3401370.54047235
     5959091.38259917 3401450.99070932
     5959010.9323622 3401338.36037757
    C  1 1
     5959063.08352122 3401386.98533277
     1 21" | format=standard output=test_polygons

    Example 1b) - standard format mode

    Sample ASCII 3D line vector map for 'standard' format mode with simplified input (note the space field separator). Note the -z flag indicating 3D vector input, and the -n flag indicating no vector header should be expected from the input file. The example can be tested in the Spearfish sample dataset:
    echo "L 5 1
    591336 4927369 1224
    594317 4925341 1292
    599356 4925162 1469
    602396 4926653 1235
    607524 4925431 1216
    1 321 " | -zn out=line3d format=standard
    This can be used to create a vector line of a GPS track: the GPS points have to be stored into a file with a preceding 'L' and the number of points (per line).

    Example 2 - point format mode

    Generate a 2D points vector map 'coords.txt' as ASCII file:

    Import into GRASS: input=coords.txt output=mymap
    As the cat option is set to 0 by default, an extra column 'cat' containing the IDs will be auto-generated.

    Example 3 - point format mode

    Generate a 2D points vector map 'points.dat' as ASCII file:
    4|1663427|5105234|mysi dira
    5|1663709|5102614|mineralni pramen

    Import into GRASS:

    cat points.dat | out=mypoints x=2 y=3 cat=1 \
        columns='cat int, x double precision, y double precision, label varchar(20)'

    The module is reading from standard input, using the default '|' (pipe) delimiter.

    Example 4 - point format mode

    Generating a 3D points vector map from DBMS (idcol must be an integer column):
    echo "select east,north,elev,idcol from mytable" | -c | -z out=mymap
    The module is reading from standard input, using the default '|' (pipe) delimiter.
    The import works for 2D maps as well (no elev column and no '-z' flag).

    Example 5 - point format mode

    Generate a 3D points vector map 'points3d.dat' with attributes as ASCII file:
    590400.5|4922820.8|143.2|mysi dira|mouse hole
    593549.3|4925500.7|442.6|mineralni pramen|mineral spring
    600375.7|4925235.6|342.2|kozi stezka|goat path

    Import into GRASS:

    #As the 'cat' option is set to 0 by default, an extra column 'cat'
    #containing the IDs will be auto-generated (no need to define that):
    cat points3d.dat | -z z=3 cat=0 out=mypoints3D \
        columns='x double precision, y double precision, z double precision, \
        label_cz varchar(20), label_en varchar(20)' -c mypoints3D mypoints3D

    Example 6 - point format mode

    Generate points file by clicking onto the map:
    #For LatLong locations:
    d.where -d -l | awk '{printf "%f|%f|point\n", $1, $2}' | out=points \
        columns='x double precision, y double precision, label varchar(20)'
    #For other projections:
    d.where | awk '{printf "%f|%f|point\n", $1, $2}' | out=points \
        columns='x double precision, y double precision, label varchar(20)'
    The 'point' string (or some similar entry) is required to generate a database table. When simply piping the coordinates (and optionally height) without additional column(s) into, only the vector map geometry will be generated.

    Example 7 - point format mode

    Convert ground control points from i.points into vector points:
    cat $MAPSET/group/$GROUP/POINTS | out=$GROUP_gcp fs=space skip=3 \
        col='x double precision, y double precision, x_target double precision, \
        y_target double precision, ok int'


    SQL command notes for creating databases


    db.execute,,,,, v.centroids, v.clean, v.db.connect,, v.out.ascii,


    Michael Higgins, U.S.Army Construction Engineering Research Laboratory
    James Westervelt, U.S.Army Construction Engineering Research Laboratory
    Radim Blazek, ITC-Irst, Trento, Italy

    Last changed: $Date$