Map calculation

Creating an attribute map

Maps of the domain type Class, ID or Group can have an attribute table with additional information on the elements in the map. An attribute table must use the same domain Class, ID or Group as the map(s) to which it refers. The domain provides the relational link between the table and the map. Therefore, the attributes in a column in an attribute table, can be put in a map, a so-called attribute map.

You can also directly create an attribute map of a raster map by typing one of the following statements on the command line of the Main window:

Syntax

OutMap = InMap.InColumn
OutMap = InMap.InTable.InColumn

where:

OutMap	is the name of your output raster map.
InMap	is the name of your input raster map (domain Class map or domain ID map).
InTable	is the name of a table (using same domain as input map).
InColumn	is the name of a column.

Notes:

The first statement only works when an attribute table is linked to the input map or to the domain of the input map (see Raster Map Properties or Domain Properties).
For the second statement, the table does not have to be linked to the map. However the statement only works when the domain that is used by the table is the same as the domain that is used by the map.

Tips:

The Attribute map of raster map operation provides the same functionality as the statements above.
To create attribute maps from polygon, segment or point maps with an attribute table: use the Attribute map of polygon map, Attribute map of segment map or Attribute map of point map operations.
When the definition symbol = is used, a dependent output map is created; when the assignment symbol := is used, the dependency link is immediately broken after the output map has been calculated.

Example

In the following example a Landuse map is used showing the geographical position of five landuse classes. In the attribute table Landuse there is a column Landuse with the description of the landuse classes and a column CommValue with the commercial value per landuse class. A new map LandValue is created showing the commercial value per landuse class.

LandValue = Landuse.CommValue

This formula works in this example because the atrribute table is linked to the domain of the input map. You may also use the expressions:

LandValue = Landuse.Landuse.CommValue

LandValue = MapAttribute(Landuse,CommValue)

Landuse

LandValue

INS	COM	RES
INS	REC	RES
COM	IND	IND

30	40	20
30	10	20
40	50	50

Landuse.tbt

Landuse	CommValue
Institutional	30
Commercial	40
Residential	20
Industrial	50
Recreational	10