How to configure a coordinate system

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Geographic Coordinate systems are configured with a set of related units.

The following example shows how to configure the Dutch coordinate system (Rijksdriehoekmeting) :

unit<float32> m := baseunit('m', float32);
unit<fpoint>   point_rd_base:
:  DialogData = "ngr_layer" 
,  Format        = "EPSG:28992";
unit<fpoint> point_rd := range(point_rd_base, point(300000[m],0[m]), point(625000[m],280000[m]));

Three units are configured:

  1. m: a baseunit for items with as metric: meter. The coordinate in the (Rijksdriehoekmeting) are expressed in meters.
  2. point_rd_base: the coordinate sytem base unit. The format property for this unit refers to EPSG:28992, the EPSG code for the Rijksdriehoekmeting. This format property is only in use for descriptive purposes. The DialogData property for this unit refers to the background layer, in the case a WMS layer.
  3. point_rd: the coordinate system unit is configured with an expression, defining the range of allowed values. The first argument of this range function refers to the coordinate system base unit, relating the set of allowed values to the coordinate system used, in this case Rijksdriehoekmeting.

If coordinate systems are configured in this way, Vector data with point_rd as values unit for it's feature attributes and Grid data relating to point_rd can be combined in the same map view. The GeoDMS supports functions for coordinate conversions, especially from and to coordinates in the (Rijksdriehoekmeting). See operator group Point for these functions.

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