Database Reference
In-Depth Information
How it works...
WehavebeenusingaspatialselfjoinofalinearPostGISspatiallayertofindinter-
sections generated by the features of that layer.
Forgeneratingthespatialselfjoin,weusedtheST_Intersectsfunction.Thiswaywe
foundallofthepairfeatureshavingatleastoneintersectionintheirrespectivegeo-
metries.
In the same self spatial join context, we found out the intersections using the
ST_Intersection
function.
Theproblemisthatthecomputedintersectionsarenotalwayssinglepoints.Infact,
twointersectinglinescanproducetheoriginforasingle-pointgeometry(
ST_Point
)
if the two lines just intersect once. But, the two intersecting lines can produce the
originforapointcollection(
ST_MultiPoint
)orevenageometriccollection,ifthe
two lines intersect at more points and/or share common parts.
As our target was to compute all of the point intersections (
ST_Point
and
ST_MultiPoint
)usingthe
ST_GeometryType
function,wefilteredoutthevalues
