[postgis-users] Which postGIS functions to use?

[gt at fks.be]

I have a "network component" (= part of a waterway) defined by 2
coordinates.
I know how to calculate the length of that component.

However, another component, let's say a quay, overlaps with the
component. I know how far it overlaps (in meters) with the component
from the beginning coordinate and I want to calculate the end coordinate
of the quay (that should be on the network component).

How do I do this?

Thank you