Well-known-text (WKT) specification

This article describes the definition and usage of WKT formatted strings in order to produce consistently georeferenced outputs.

For a detailed description of the WKT format including a list of the various fields, please refer to this documentation.

User interface

CLI
–coordinate_system <path> 
–no_coordinate_system

The "-coordinate_system <path>" parameter lets you specify the path to an ASCII file containing the WKT string, the actual file extension is irrelevant (can be for example .txt, .wkt, .prj). During project generation with SURE, the specified file will be read and stored as "coordinate_system.wkt" within your project directory.

WKT strings given within MatchAT PRJ files will be parsed automatically and set as project coordinate system. You can suppress the automatic input of WKT information from PRJ files by using the "-no_coordinate_system" flag. In case a coordinate system is given within a PRJ file, the use of the "-coordinate_system <path>" parameter will overwrite this coordinate system with the one specified.

GUI

You can specify the coordinate system either during project setup or after project creation within the advanced configuration. Thereto edit the "Coordinate System" field among the Key Parameters and insert the WKT string directly. As opposed to the command line interface, you cannot specify any path to ASCII files containing the WKT string here, instead copy the WKT string itself into the text box.

The specified WKT string will be stored as "coordinate_system.wkt" within you project directory.


Georeferenced outputs

Important

The information given in the WKT string defines the coordinate system your input data is given in (e.g. shape files, project coordinate system) and will also be attached to your output data (e.g. TIFF headers, point cloud headers). Specifying a different coordinate system than the input data is actually given in will not transform your output data into that system.

Mesh outputs: Cesium, lod_dae, lod_obj, slpk

Several mesh output formats that can be generated with SURE require you to specify a WKT coordinate system. These are: Cesium, lod_dae, lod_obj and slpk. The lod_dae and lod_obj additionally require that the "EPSG" field is specified within the "PROJCS" field of the WKT string.

Troubleshooting

Inconsistent coordinate system definition

When using shape file inputs (e.g. area shapes for Area / ROI definition), make sure that the shape files are defined within the same coordinate system that is specified for your project:

  • If two different global systems are defined, an error message will be displayed and the project cannot be processed.
  • If two different systems are defined, where one system is either undefined or defined as "Local System" and the other one is a global system, SURE will display a warning message. However, processing will be continued using the WKT information specified as project coordinate system.

Examples

Full coordinate system definition including EPSG tags
PROJCS["ETRS89 / UTM zone 32N", 
GEOGCS["ETRS89",DATUM["European_Terrestrial_Reference_System_1989",
SPHEROID["GRS 1980",6378137,298.257222101,AUTHORITY["EPSG",
"7019"]],
AUTHORITY["EPSG","6258"]],
PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],
UNIT["degree",0.01745329251994328,
AUTHORITY["EPSG","9122"]], AUTHORITY["EPSG","4258"]],
UNIT["metre",1,AUTHORITY["EPSG","9001"]],
PROJECTION["Transverse_Mercator"],
PARAMETER["latitude_of_origin",0],
PARAMETER["central_meridian",9],
PARAMETER["scale_factor",0.9996],
PARAMETER["false_easting",500000],
PARAMETER["false_northing",0],
AUTHORITY["EPSG","25832"],
AXIS["Easting",EAST],
AXIS["Northing",NORTH]]


Local coordinate system
LOCAL_CS["Local Space Rectangular (LSR)",
UNIT["m",1]]