WKT and WKB (OGC Simple Features)

OGC Simple Feature Access (ISO 19125) serialization for Geometry<T> — one geometry model, three encodings: OGC Well-Known Text, Well-Known Binary, and SQL Server's WKT dialect.

Supported capabilities

Capability	Supported
OGC WKT read	Yes — WktReader.Parse
OGC WKT write	Yes — geometry.AsWkt()
WKB read	Yes — Geometry<T>.FromWkb / WkbReader.Parse
WKB write	Yes — geometry.AsWkb()
SQL Server WKT read	Yes — SqlServerWktReader.Parse
SQL Server WKT write	Yes — geometry.AsSqlServerWkt()
Z / M / ZM dimensions	Yes (WKT dimension suffixes)

A polygon's rings carry two different meanings: an interior ring is a hole in the same polygon, while a second exterior ring is a separate part of a MultiPolygon.

Usage

WKT — Well-Known Text

WktReader parses OGC-compliant WKT, including the Z / M / ZM dimension suffixes; AsWkt() writes it back.

using IRI.Maptor.Core.Spatial.IO.OgcSFA;

var geometry = WktReader.Parse("POINT Z (1 2 3)", srid: 4326);

string wkt = geometry.AsWkt();   // "POINT Z (1 2 3)"

WKB — Well-Known Binary

The compact binary twin: one byte-order flag, a uint32 geometry type, then raw double coordinates.

byte[] wkb = geometry.AsWkb();               // POINT: 21 bytes = order(1) + type(4) + x(8) + y(8)

var restored = Geometry<Point>.FromWkb(wkb, srid: 4326);

Byte-level layout of every geometry type: WKB_Binary_Structure.md.

The SQL Server dialect

SQL Server writes WKT without dimension suffixes — the dimension is inferred from the coordinate count (POINT (1 2 3) instead of OGC's POINT Z (1 2 3)). SqlServerWktReader / AsSqlServerWkt() speak that dialect, so converting is a read in one and a write in the other:

var g = SqlServerWktReader.Parse("POINT (1 2 3)");

string ogc = g.AsWkt();            // "POINT Z (1 2 3)"
string sql = g.AsSqlServerWkt();   // "POINT (1 2 3)"

Full comparison (dimension detection, MULTIPOINT nesting, when to use which): WKT_SqlServer_Differences.md.

The OGC object model

The interchange types the WKB layer is built around — OgcPoint, OgcLineString, OgcPolygon, the Multi* classes and the WkbGeometryType enum — live in the IRI.Maptor.Core.Ogc.SFA namespace of the IRI.Maptor.Core.Ogc project.

---

Back to IRI.Maptor.Core.Spatial