rescale_measures: Rescale Aggregate id Measure to id Measure
Description
Given a aggregate id (e.g. reachcode) measure and the from and
to measure for a id (e.g. comid flowline), returns the measure along the
id line. This is a utility specific to the NHDPlus data model where
many comid flowlines make up a single reachcode / reach. "Measures"
are typically referenced to reaches. Flowlines have a stated from-measure /
to-measure. In some cases it is useful to rescale the measure such that it
is relative only to the flowline.
from is downstream -- 0 is the outlet
to is upstream -- 100 is the inlet