WKT - Well-Known Text
- OGC Standard - See Section 7.
- Wikipedia
Well-known text (WKT) for geometry is a text markup language for representing vector geometry objects. It is specified in the OGC Simple Feature Access standard (ISO/IEC 13249-3:2016).
- WKT should not be confused with WKT CRS which describes spatial reference systems.
- WKT has a binary equivalent, well-known binary WKB, which is a more compact, but non human-readable form.
Examples
| Geometry Type | WKT Example | Description |
|---|---|---|
| Point | POINT(30 10) | A single point with x coordinate 30 and y coordinate 10 |
| LineString | LINESTRING(30 10, 10 30, 40 40) | A line connecting three points with x and y coordinates |
| Polygon | POLYGON((30 10, 40 40, 20 40, 10 20, 30 10)) | A polygon with five vertices and an interior ring |
| MultiPoint | MULTIPOINT((10 40), (40 30), (20 20), (30 10)) | Four points with x and y coordinates |
| MultiLineString | MULTILINESTRING((10 10, 20 20, 10 40), (40 40, 30 30, 40 20, 30 10)) | Ttwo line strings, each connecting multiple points |
| MultiPolygon | MULTIPOLYGON(((30 20, 45 40, 10 40, 30 20)),((15 5, 40 10, 10 20, 5 10, 15 5))) | Two polygons |
| GeometryCollection | GEOMETRYCOLLECTION(POINT(10 40), LINESTRING(30 10, 10 30, 40 40) | A collection of geometries |
| Point ZM | POINT ZM (1 2 3 4) | A point with x, y, z, and m values of 1, 2, 3, and 4 |
| Point M | POINT M (1 2 3) | A point with x, y, and m values of 1, 2, and 3 |
Variants
| Format | Support | Description |
|---|---|---|
| EWKT | ❌ | WKT that starts with a spatial reference id (SRID) |
Alternatives
| Format | Notes |
|---|---|
| WKT | (This format) Arguably the easiest for humans to read. |
| WKB | Binary, more compact |
| GeoJSON Geometry | JSON based, human-readable, slightly more verbose, easier to parse |
| GML Geometry | XML based, human-readable, even more verbose, more complex to parse |
Ecosystem Support
- PostGIS and some other databases offer functions to return geometries in WKT format: WKT, ST_AsEWKT.
Geometries
WKT can represent a range of distinct geometric objects.
Note that some implementations, including loaders.gl, only handle the core GeoJSON geometry equivalents (points, line strings, polygons and to a varying degrees geometry collections of the same).
| Geometry |
|---|
Point, MultiPoint |
LineString, MultiLineString |
Polygon, MultiPolygon |
GeometryCollection |
Triangle |
PolyhedralSurface |
TIN (Triangulated irregular network) |