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Selecting with the Web API

Creating Geometry Objects From Features

selection filters spatial spatial filtersSpatial Filters
With spatial filters,
you can do comparisons using geometric properties. For example,
you can select all features that are inside an area on the map,
or that intersect an area.
There are two ways
of using spatial filters:
- Create a separate spatial filter to apply
to the feature source, using the MgFeatureQueryOptions::SetSpatialFilter() method.
- Include spatial properties in a basic filter
created with the MgFeatureQueryOptions::SetFilter() method.
The MgFeatureQueryOptions::SetSpatialFilter() method
requires an MgGeometry object to define
the geometry and a spatial operation to compare the feature property
and the geometry. The spatial operations are defined in class MgFeatureSpatialOperations.
To include spatial
properties in a basic filter, define the geometry using WKT format.
Use the GEOMFROMTEXT() function
in the basic filter, along with one of the following spatial operations:
- CONTAINS
- COVEREDBY
- CROSSES
- DISJOINT
- EQUALS
- INTERSECTS
- OVERLAPS
- TOUCHES
- WITHIN
- INSIDE
NoteNot
all spatial operations can be used on all features. It depends on
the capabilities of the FDO provider that supplies the data. This
restriction applies to separate spatial filters and spatial properties
that are used in a basic filter.