GRASS GIS manual: v.out.ascii

NAME

v.out.ascii - Exports a vector map to a GRASS ASCII vector representation.

KEYWORDS

vector, export, ascii

SYNOPSIS

v.out.ascii
v.out.ascii help
v.out.ascii [-ocr] input=name layer=string [output=name] [columns=name[,name,...]] [where=sql_query] format=string [fs=character] [dp=integer] [--overwrite] [--verbose] [--quiet]

Flags:

-o: Create old (version 4) ASCII file
-c: Include column names in output (points mode)
-r: Only export points falling within current 3D region (points mode)
--overwrite: Allow output files to overwrite existing files
--verbose: Verbose module output
--quiet: Quiet module output

Parameters:

input=name: Name of input vector map; Data source for direct OGR access
layer=string: Layer number or name; A single vector map can be connected to multiple database tables. This number determines which table to use. Layer name for direct OGR access.; Default: 1
output=name: Path to resulting ASCII file ('-' for standard output) or ASCII vector name if '-o' is defined; Default: -
columns=name[,name,...]: Name of attribute column(s) to be exported (point mode)
where=sql_query: WHERE conditions of SQL statement without 'where' keyword; Example: income < 1000 and inhab >= 10000
format=string: Output format; Options: point,standard,wkt; Default: point
fs=character: Field separator; Field separator (points mode); Default: |
dp=integer: Number of significant digits (floating point only); Options: 0-32; Default: 8

DESCRIPTION

v.out.ascii converts a GRASS vector map in binary format to a GRASS vector map in ASCII format. Using flag -o v.out.ascii output will be in old (version 4) ASCII format.

If the output parameter is not given then the coordinates of any point data within the vector map is sent to stdout.

NOTES

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

If the format parameter is set to standard, a GRASS ASCII vector map will be exported, which may contain a mix of primitives including points, lines, boundaries, centroids, areas, faces, and kernels. The beginning of the output ascii file will contain a header listing any metadata for the input vector map, if such metadata exists. An example of the standard format is given below.

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

ORGANIZATION
DIGIT DATE
DIGIT NAME
MAP NAME
MAP DATE
MAP SCALE
OTHER INFO
ZONE
WEST EDGE
EAST EDGE
SOUTH EDGE
NORTH EDGE
MAP THRESH

The body begins with the row:

VERTI:

followed by records of primitives:

TYPE NUMBER_OF_COORDINATES [NUMBER_OF_CATEGORIES]
 X Y [Z]
....
 X Y [Z]
[ LAYER CATEGORY]
....
[ LAYER CATEGORY]

Everything above in [ ] is optional.

The primitive codes are as follows:

'P': point
'L': line
'B': boundary
'C': centroid
'F': face (3D boundary)
'K': kernel (3D centroid)
'A': area (boundary) - better use 'B'; kept only for backward compatibility

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.

Only features with a category number will be exported. Use v.category to add them if needed.

v.out.ascii does not copy the dig_cats file associated with the binary vector input map to the new output file name. The user must copy the dig_cats file to the new output name if this is desired (e.g. using the UNIX cp command).

It is possible to output the coordinates of vertices in a non-points vector feature by first converting the vector feature to a points map with v.to.points and then exporting with v.out.ascii in points mode.

EXAMPLES

Standard mode

v.out.ascii input=quads format=standard

ORGANIZATION: US Army Const. Eng. Rsch. Lab
DIGIT DATE:   May 1987
DIGIT NAME:   grass
MAP NAME:     Quads
MAP DATE:     May 1987
MAP SCALE:    24000
OTHER INFO:
ZONE:         13
MAP THRESH:   18.288000
VERTI:
B  4
 599587.1820962 4914067.53414294
 589639.15126831 4913922.5687301
 589440.96838162 4927803.62500018
 599375.87959179 4927959.83330436
B  2
 599375.87959179 4927959.83330436
 599587.1820962 4914067.53414294
B  4
 599587.1820962 4914067.53414294
 609541.5508239 4914236.0597482
 609316.10665227 4928116.8490555
 599375.87959179 4927959.83330436
C  1 1
 594125.63    4921115.58
 1     1
C  1 1
 604433.84    4921087.1
 1     2

Point mode

v.out.ascii input=quads format=point

594125.63|4921115.58|1
604433.84|4921087.1|2

v.out.ascii input=archsites format=point where="cat > 5 and cat <= 8" columns=str1

600375|4925235|6|Prairie Site
606635|4920773|7|Jensen Pass
595755|4925300|8|No Name

AUTHORS

Michael Higgins, U.S. Army Construction Engineering Research Laboratory
James Westervelt, U.S. Army Construction Engineering Research Laboratory
Radim Blazek, ITC-Irst, Trento, Italy
Attribute selection added by Martin Landa, CTU in Prague, Czech Republic (2008/12)

Last changed: $Date: 2010-02-16 23:56:50 -0800 (Tue, 16 Feb 2010) $

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