The well-known binary representation for geometry is designed to represent instances of the geometry types described in the geometry object model and in the OpenGIS Abstract Specification.

These assertions imply the following for rings, polygons, and multipolygons:

• Linear rings—Rings are simple and closed, which means that linear rings may not self intersect.
• Polygons—No two linear rings in the boundary of a polygon may cross each other. The linear rings in the boundary of a polygon may intersect, at most, at a single point but only as a tangent.
• Multipolygons—The interiors of two polygons that are elements of a multipolygon may not intersect. The boundaries of any two polygons that are elements of a multipolygon may touch at only a finite number of points.

An 'unsigned integer' is a 32-bit (4 byte) data type that encodes a nonnegative integer in the range [0, 4294967295].

A 'double' is a 64-bit (8 byte) double-precision data type that encodes a double-precision number using the IEEE 754 double-precision format.

The above definitions are common to both XDR and NDR.

XDR (big endian) encoding of numeric types

The XDR representation of an unsigned integer is big-endian (most significant byte first).

The XDR representation of a double is big-endian (sign bit is first byte).

NDR (little endian) encoding of numeric types

The NDR representation of an unsigned integer is little-endian (least significant byte first).

The NDR representation of a double is little-endian (sign bit is last byte).

Conversion between the NDR and XDR representations of WKB geometry

Conversion between the NDR and XDR data types for unsigned integers and doubles is a simple operation involving reversing the order of bytes within each unsigned integer or double in the byte stream.

The well-known binary representation for geometry is described below. The basic building block is the byte stream for a point that consists of two doubles. The byte streams for other geometries are built using the byte streams for geometries that have already been defined.

// Basic Type definitions // byte : 1 byte // uint32 : 32 bit unsigned integer (4 bytes) // double : double precision number (8 bytes) // Building Blocks : Point, LinearRing Point { double x; double y; }; LinearRing { uint32 numPoints; Point points[numPoints]; } enum wkbGeometryType { wkbPoint = 1, wkbLineString = 2, wkbPolygon = 3, wkbMultiPoint = 4, wkbMultiLineString = 5, wkbMultiPolygon = 6, wkbGeometryCollection = 7 }; <>enum wkbByteOrder { wkbXDR = 0,// Big Endian wkbNDR = 1 // Little Endian }; WKBPoint { byte byteOrder; uint32 wkbType; // 1 Point point; } WKBLineString { byte byteOrder; uint32 wkbType;// 2 uint32 numPoints; Point points[numPoints]; } WKBPolygon { byte byteOrder; uint32 wkbType;// 3 uint32 numRings; LinearRing rings[numRings]; } WKBMultiPoint { byte byteOrder; uint32 wkbType;// 4 uint32 num_wkbPoints; WKBPoint WKBPoints[num_wkbPoints]; } WKBMultiLineString { byte byteOrder; uint32 wkbType;// 5 uint32 num_wkbLineStrings; WKBLineString WKBLineStrings[num_wkbLineStrings]; } wkbMultiPolygon { byte byteOrder; uint32 wkbType;//6 uint32 num_wkbPolygons; WKBPolygon wkbPolygons[num_wkbPolygons]; } WKBGeometry { union {  WKBPoint point;  WKBLineString linestring;  WKBPolygon polygon;  WKBGeometryCollection collection;  WKBMultiPoint mpoint;  WKBMultiLineString mlinestring;  WKBMultiPolygon mpolygon; } }; WKBGeometryCollection { byte byte_order; uint32 wkbType;// 7 uint32 num_wkbGeometries; WKBGeometry wkbGeometries[num_wkbGeometries] }

Well-known binary representation for a geometry object in NDR format (B=1) of type polygon (T=3) with two linears (NR = 2) and each ring having three points (NP = 3).