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Establishing Upstream and Downstream Node Ids for single line segments

Question asked by ta199103 on Apr 24, 2017

I have a drainage network set up over the course of several city blocks. I have two distinct point files and one linear file. The two point files are junctions and inlets. Both junctions and inlets have distinct "node id" attribution respectively. Junctions are arbitrary points along the curb line with elevation data extracted from DEM source. Inlets are legitimate drains that the city has installed with their elevations also derived from the same DEM source. The linear file portrays the flow along the curb for the study area. Each line is snapped on either end to either a junction or inlet. So for instance the network would look like this:

----------x------------x----------I-----------x-----------I (x denotes junction, dashed line denotes the flow path/drainage line, and I denotes Inlet)

I'm trying to get the node id attribution from the point files joined to the linear file in the direction the water flows. All linear work is derived from connecting the dots from highest elevation to lowest elevation along the curb line. I'd like the upstream node id to denote the elevation of the point with the higher elevation attribute and the downstream node id to denote the elevation of the point on the downslope end of the line. Any thoughts? I'm by no means a python expert and have tried a succession of spatial joins but find it's not establishing the upstream/downstream ids based off the elevation data...