WellKnownTextFlavor Enumeration
Represents the flavor of Well-Known Text used to describe Coordinate Reference Systems.
NuGet/Assembly: Carmenta.Engine.5.16.2.nupkg (in the CECore assembly)
Syntax
public enum WellKnownTextFlavorValues
| Value name | Value | Description |
|---|---|---|
| OgrWellKnownText | 0 | The WKT1 flavor used by the GDAL/OGR library. |
| EsriWellKnownText | 1 | The WKT1 flavor used by ESRI. |
| WellKnownText2_2015 | 2 | The 2015 version of WKT2. |
| WellKnownText2_2019 | 3 | The 2019 version of WKT2. |
Remarks
Well-Known Text, or WKT, is a standard for machine- and human-readable text that can represent both geometries and Coordinate Reference Systems. However, this enumeration of WKT flavors concerns only Coordinate Reference Systems.
The original standard for the WKT representation of Coordinate Reference Systems was published in the Simple Features documents (references 1, 2 and 3), and was later extended (reference 4). However, it turned out that the standard could be interpreted in different ways, and different GIS vendors developed their own flavors (or dialects) of WKT for Coordinate Reference Systems; see Warmerdam (ref. 5) and Schmidt (ref. 6).
In 2015 and 2019, ISO and OGC jointly published revised specifications of WKT (references 7 and 8). These modern versions are informally known as WKT2, or as WKT2:2015 and WKT2:2019 (although the term "WKT2" is not used in the specifications), and the older versions have retroactively been labeled as WKT1. In the GDAL/OGR library, our four flavors have the names WKT1_GDAL, WKT1_ESRI, WKT2_2015 and either WKT2_2018 or WKT2_2019 (the publication was expected in 2018 but was delayed to 2019).
Most of the ambiguities in WKT1 can be resolved when writing WKT2. The ten WKT1 examples listed by Schmidt show how different GIS vendors used different names for projection methods and projection parameters; in WKT2, the names can be complemented by the unambiguous EPSG code numbers for the methods and parameters. But the code numbers are not mandatory in WKT2, so it is still possible to write WKT2 that is valid but has limited interoperability.
References
ISO 19125-1:2004, Geographic information – Simple feature access – Part 1: Common architecture.
OGC Project Document 99-036, OpenGIS Simple Features Specification for SQL, revision 1.1.
OGC Project Document 06-103r4, Simple feature access – Part 1: Common architecture.
OGC Project Document 01-009, OpenGIS Implementation Specification: Coordinate Transformation Services, revision 1.00, January 2001.
F. Warmerdam. OGC WKT Coordinate System Issues, 2007 (revised 2018).
C. Schmidt. The WKT of Babel, 2008.
Roger Lott (ed.), Geographic information – Well-Known Text representation of coordinate reference systems, version 1.0, 2015. Published both as ISO 19162:2015(E) and as OGC 12-063r5.
Roger Lott (ed.), Geographic information – Well-Known Text representation of coordinate reference systems, version 2.0.6, 2019. Published both as ISO 19162:2019 and as OGC 18-010r7.
Platforms
Windows, Linux, Android