Using Geometry Functions | 39
Using Geometry Functions
Using new enhanced layer functionality, you can apply geometry functions
to selected features on maps drawn from spatial data provider (SDP) data
sources. For example, you can apply a geometry function to a point layer in
a map that shows the locations of cell phone towers. This function could
direct Oracle to apply a buffer of a size equivalent to the range of each tower.
By analyzing the buffered towers on the map, you could see where there are
gaps between towers’ ranges, indicating places where cell phone coverage
may not be available.
Note You can only apply geometry functions to maps drawn from SDP data.
Layers created from OLE database data do not support geometry functions.
New geometry functions apply to all layer types and GIS functions that
Oracle supports. Advanced calculations required for the addition of buffers,
centroid locations, and other geometry functions are performed by Oracle on
the server side where the data resides, and are passed back to the Autodesk
MapGuide client application. You can take advantage of Oracle’s powerful
geometry capabilities and quickly bring the results into your projects.
Note Currently, only Oracle supports geometry functions, and geometry func-
tions must return geometry objects, such as points, polygons, polylines, or some
combination of these objects. Also, the Autodesk MapGuide layer type must
match the geometry type returned by the geometry function used.
To apply the Oracle geometry function
1 Double-click the name of the layer in the list. The Map Layer Properties
dialog box is displayed.
2 To display its contents, click the Data Sources tab.
3 On the Data Sources tab, in the Geometry Function text box, enter the
name of the geometry function you want to apply.
4 Click OK. The Map Layer Dialog box is closed, and the Oracle layer is buff-
ered using Oracle’s geometry function. The results are displayed on the
layer.
Example: Suppose you are applying the buffer geometry function, for which
you would enter
SDO_GEOM.SDO_BUFFER(%GEOMCOL,2,1)
The selected geometry column name for the layer is substituted for the
%GEOMCOL parameter if it is used.
