point_on_line
Finds a point on a line geometry, a given distance along it from its start or end point. With a 3D line, the height will be interpolated between vertices.
Parameter 1 - the input geometry.
Parameter 2 - distance from the start of the line. A negative value indicates distance from the end of the line.
Returns: a point geometry. Returns null if the distance parameter is out of range or if parameter 1 is not a simple line.