/ Filters / Chapter 35. Using spatial properties of features in filters / Numbers of feature intersections and inclusions

Relations and their variants

The considered group of properties is used to evaluate the number of argument features intersecting the tested feature or including it, therefore comparison relations and relations of diapasons/intervals are applicable for them (see chapter 26 “Searching records in a table”, table 26-2 and table 26-3). For comparison relations it is also required to specify one numerical operand with which feature number will be compared, and for relations of diapasons/intervals two operands are required (diapason limits). However in this case, in contrast to the property groups considered above, the only admissible relation variant is Count. It means that a specified comparison relation or relation of diapasons/intervals is applied to the number of argument features which are in the specified relative placement with the tested feature.

Thus, there is a possibility to build, for instance, such simple conditions of feature filtration:

the water-pipe intersects territory of at least two parcels;

there are more than 5 buildings in the block.

Another relation applicable to the relative placement properties is the special relation B (in place of “Boolean”) which allows determine the very fact of intersection or non-intersection of the tested feature with argument features but does not find out the concrete number of these intersection or inclusions.

The possible variants of the B relation are shown in the table 35-3. This relation does not require numerical operands.

Table 35-3. Variants of B relation for relative placement properties

The relation is introduced for more convenient and clear expression of some frequently used conditions. In principle, it can be replaced by comparison of the appropriate property with zero. For instance, the condition “There is an inclusion into any of argument feature” is equivalent to the condition “The number of inclusions is greater than 0” and the condition “There are intersections with each of argument features” is equivalent to “The number of argument features non-intersecting with the tested one equals 0”.