WKB

Well-Known Binary (WKB) is a binary encoding for geometric objects used in geographic information systems (GIS). It serves as the binary counterpart to Well-Known Text (WKT), providing a compact and efficient means to store and transmit geometry data between applications and databases. The format was defined by the Open Geospatial Consortium (OGC) as part of the Simple Features standard.

An instance of WKB begins with a byte that indicates byte order (endianness): 1 for little-endian, 0 for big-endian. This is followed by a four-byte unsigned integer encoding the geometry type (for example, Point, LineString, Polygon, and their multi- and collection variants). The remaining bytes encode the coordinates in a fixed binary representation, typically as 64-bit floating point values. Some implementations extend WKB to include additional dimensions such as Z (height) and M (measure). For purely geometric data, WKB remains compact and efficient; WKT remains human-readable.

Extended variants include EWKB (Extended Well-Known Binary) used by PostGIS, which can carry a spatial reference identifier (SRID) and can flag the presence of Z or M coordinates. There is also EWKT for the textual counterpart, and many libraries provide utilities to parse and generate WKB/EWKB.

Applications and support: WKB is widely adopted in spatial databases, GIS software, and data interchange. Libraries and systems such as GEOS, OGR, Shapely, and PostGIS provide robust support for reading and writing WKB, enabling interoperability across platforms and programming languages. Because it is binary, WKB is typically not human readable and is optimized for machine processing and network transmission.