Base Grid

A grid defines a two-dimensional structure in which each cell has a value. But for some operators-and-functions many cells might be irrelevant. Think for example of a Allocation function that does not allocate sea cells.

If the number of irrelevant cells is substantial, it is more efficient to apply operators and functions on a subset of the grid cells. This subset only contains the cells that are relevant. A Base Grid attribute is configured as the relation for the grid domain unit towards the one-dimensional subset domain (usually a uint32 domain-unit). This basegrid is used to convert the results at the subset domain back to the original grid domain. This is necessary for the visualisation in a Map View.

example

attribute<bool> IsAllocatable (GridDomain) := LandUseType == luEndogenous

unit<uint32> FreeLandCells := select_with_org_rel(IsAllocatable)
{
   attribute<FreeLandCells> permutation                  := rnd_permutation(0, rnd_FreeLandCells);
   attribute<GridDomain>    org_rel2     (FreeLandCells) := org_rel[permutation];
   attribute<FreeLandCells> BaseGrid     (GridDomain)    := invert(org_rel2);
}

attribute<dollar_ha>                     Residential  (FreeLandCells) 
   := SuitabilityMap/Residential[FreeLandCells/nr_OrgEntity2];
attribute<Classifications/LU/Endogenous> landuse_grid (GridDomain)    
   := landuse[Compact/FreeLandCells/BaseGrid];

• The IsAllocatable attribute is a boolean attribute defining the condition for the selection of allocatable cells.
• The FreeLandCells unit is the domain unit of the allocatable cells. A random permutation is used in this domain to process all grid cells in a random order. This is usefull if the suitability maps are not distinctive enough, resulting in multiple cells with the same suitability. The random order prevents in this situation an allocation mainly derived from the grid cell coordinate.
• The BaseGrid attribute defines the relation from the GridDomain domain unit towards the FreeLandCells domain.
• The Residential attribute presents an example of how to relate an attribute (in this case the suitability map for Residential) from the GridDomain towards the FreeLandCells domain.
• The landuse_grid attribute presents an example of how to to relate the results of the allocation at the FreeLandCells domain backwards to the GridDomain.