I try to understand the
ST_LocateAlong/ST_LocateBetween PostGIS function. The documentation tells me this:
geometry ST_LocateAlong(geometry ageom_with_measure, float8 a_measure, float8 offset);
Return a derived geometry collection value with elements that match the specified measure. Polygonal elements are not supported.
If an offset is provided, the resultant will be offset to the left or right of the input line by the specified number of units. A positive offset will be to the left, and a negative one to the right.
I understand that a point will be returned if feed in a LineM and a measure. But what is the use of an offset? Will the output point be shifted?
Similar to the offset in
ST_LocateBetween - Will the output line substring be shifted? The documentation of
ST_LocateBetween does not touch the parameter offset.
I know that I would just have to try it but I am still missing these skills, nevertheless I do need the information.