How flat-Earth and round-Earth representations work
SAP Sybase IQ supports both flat-Earth and round-Earth representations. Flat-Earth reference systems project all or a portion of the surface of the Earth to a flat, two dimensional plane (planar), and use a simple 2D Euclidean geometry. Lines between points are straight (except for circularstrings), and geometries cannot wrap over the edge (cross the dateline).
How interpolation impacts spatial calculations
Interpolation is the process of using known points in a geometry to approximate unknown points. Several spatial methods and predicates use interpolation when the calculations involve circular arcs. Interpolation turns a circular arc into a sequence of straight lines. For example, a circularstring representing a quarter arc might be interpolated as a linestring with 11 control points.
How spatial comparisons work
There are two methods you can use to test whether a geometry is equal to another geometry: ST_Equals, and ST_OrderingEquals. These methods perform the comparison differently, and return a different result.
How spatial relationships work
For best performance, use methods like ST_Within, or ST_Touches to test single, specific relationships between geometries. However, if you have more than one relationship to test, ST_Relate can be a better method, since you can test for several relationships at once. ST_Relate is also good when you want to test for a different interpretation of a predicate.
How spatial dimensions work
As well as having distinct properties of its own, each of the geometry subtypes inherits properties from the ST_Geometry supertype. A geometry subtype has one of the following dimensional values:
Created December 19, 2013. Send feedback on this help topic to Technical Publications:
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