How many lines can a MultiLineString intersect at?
The LineString instances can only intersect or touch themselves or other LineString instances at a finite number of points. The following example shows three valid MultiLineString instances and one MultiLineString instance that is not valid.
Do you have to have a MultiLineString instance?
All instances comprising the MultiLineString instance must be valid LineString instances. No two LineString instances comprising the MultiLineString instance may overlap over an interval. The LineString instances can only intersect or touch themselves or other LineString instances at a finite number of points.
How to return the nth point in a LineString?
Return the Nth point in a single linestring or circular linestring in the geometry. Negative values are counted backwards from the end of the LineString, so that -1 is the last point. Returns NULL if there is no linestring in the geometry. Index is 1-based as for OGC specs since version 0.8.0.
What is a MultiLineString object in pgRouting?
A MULTILINESTRING object consists of 1 to m LINESTRINGs. In case of a routing network, it’s not obvious to me why MULTILINESTRINGs would be used. If you plan to use pgRouting’s shortest path function, the geometries are irrelevant anyway since it only needs source and target vertex ids for every edge.
Why is Figure 6 a closed MultiLineString instance?
Figure 6 is a simple, closed MultiLineString instance. It is closed because all its elements are closed. It is simple because none of its elements intersect at the interiors. For a MultiLineString instance to be accepted it must either be empty or comprised of only LineString instances that are accepted.
Which is a nonsimple MultiLineString instance in SQL?
Figure 3 is a nonsimple MultiLineString instance because the interior of one of its LineString elements is intersected. The boundary of this MultiLineString instance is the four endpoints. Figure 4 is a nonsimple, nonclosed MultiLineString instance.