I want to show how steep a given stream is, with PostGIS and QGIS.
My thought process for solving this problem of steepness is as follows: 1). Given Raster and Multilinestring data, combine them into a MultilineStringZ column 2). Perform some elementary calculus on the new MultilineStringZ column to find steeper sections. Colorize them in QGIS if possible to examine the results.
Stream Data as MultilineString:
I need a better understanding on how a MultilineString and a raster layer are combined to create a 3D stream, or alternatives to completing the task of encoding "steepness" into line strings.