Gridset

unit-functions gridset

syntax

• gridset(coordinate_unit, size, offset, valuetype)

definition

gridset(coordinate_unit, size, offset, valuetype) configures a grid-domain with a projection to a coordinate system.

The gridset function has the following arguments:

• the baseunit in which the coordinates of the coordinatesystem are expressed;
• the size of the grid cells in both X and Y directions, expressed in the base-unit;
• the offset, the coordinates of the top left coordinate, expressed in the base unit;
• the value-type of the resulting domain-unit (in earlier versions the value type was configured as string, this is not supported anymore).

applies to

• unit baseunit with a Point value type
• parameter or literal size is with a Point value type
• parameter or literal offset is with a Point value type
• valuetype with a Point value type of the group CanBeDomainUnit

conditions

The values-unit of the baseunit, size and offset arguments must match.

be aware

The evaluation of a gridset, like the baseunit is executed when the meta/scheme information is generated in the geodms-gui. If for this evaluation (large) primary files are read, this becomes times consuming. Expanding tree items in the treeview becomes slow. Therefor we advice to use the contents of large primary data file (or complex calculations) as little as possible in configuring gridsets.

If multiple geographic grid domains are needed, use the range function with arguments that might result from primary data and a gridset with arguments not dependent on primary data (see example 2). The variable arguments of the range are not part of the meta/scheme information and do not influence the speed in expanding tree items in the GUI.

example

unit<fpoint> rdc_m := range(fpoint, point(300000f,0f), point(625000f,280000f))
,  label = "rijksdriehoekmeting in meters";

1. unit<spoint> rdc_100 := range(
      gridset(
          rdc_m
         ,point(  -100f,   100f, rdc_m)
         ,point(625000f, 10000f, rdc_m)
         ,spoint
      )
      ,point(   0s,    0s)
      ,point(3250s, 2700s)
   );

2. unit<ipoint> ahn_tiles_gridset :=
      gridset(
               point_rd
              ,point(-0.5[m], 0.5[m], point_rd)
              ,point(0f, 0f, point_rd)
              ,ipoint
      );
   unit<ipoint> ahn_tile_I:=
      range(
            ahn_tiles_gridset
    	   ,point(bbox/y_max, bbox/x_min, point_rd)[ahn_tiles_gridset]
	   ,point(bbox/y_max, bbox/x_min, point_rd)[ahn_tiles_gridset] 
            + point(nr_rows_int32, nr_cols_int32, ahn_tiles_gridset)
      );