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18.3.2. Well-Known Binary (WKB) Format

The Well-Known Binary (WKB) representation for geometric values is defined by the OpenGIS specification. It is also defined in the ISO SQL/MM Part 3: Spatial standard.

WKB is used to exchange geometry data as binary streams represented by BLOB values containing geometric WKB information.

WKB uses one-byte unsigned integers, four-byte unsigned integers, and eight-byte double-precision numbers (IEEE 754 format). A byte is eight bits.

For example, a WKB value that corresponds to POINT(1 1) consists of this sequence of 21 bytes (each represented here by two hex digits):


The sequence may be broken down into these components:

Byte order : 01
WKB type   : 01000000
X          : 000000000000F03F
Y          : 000000000000F03F

Component representation is as follows:

  • The byte order may be either 0 or 1 to indicate little-endian or big-endian storage. The little-endian and big-endian byte orders are also known as Network Data Representation (NDR) and External Data Representation (XDR), respectively.

  • The WKB type is a code that indicates the geometry type. Values from 1 through 7 indicate Point, LineString, Polygon, MultiPoint, MultiLineString, MultiPolygon, and GeometryCollection.

  • A Point value has X and Y coordinates, each represented as a double-precision value.

WKB values for more complex geometry values are represented by more complex data structures, as detailed in the OpenGIS specification.

  Published under the terms of the GNU General Public License Design by Interspire