GRASS GIS Manual: GRASS ASCII vector format specification

## GRASS ASCII vector format specification

A vector map in GRASS native vector format may contain a mix of primitives including points, lines, boundaries, centroids, areas, faces, and kernels. The GRASS ASCII vector format may contain also a header with various metadata (see example 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 coordinates 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 format, the order of coordinates was different:

    Y X

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.MMMMMh`
- `DDD:MM:SSh`
- `DDD:MM:SS.SSSSSh`

## EXAMPLES

    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
    VERTI:
    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

In this case the vector map contains 2 boundaries (first boundary with 6 vertices, second with 4 vertices) without category and 2 centroids with category number 20 and 21 (layer 1).

## SEE ALSO

v.in.ascii, v.out.ascii, v.edit

## SOURCE CODE

Available at: GRASS ASCII vector format specification source code (history)

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© 2003-2016 GRASS Development Team, GRASS GIS 7.2.0 Reference Manual