Research Request - "super" project to deal with inlining / looping routes

[tiffanychu90]

Complete the below when receiving a research request, and continue to add to this issue as you receive additional details and produce deliverables. Be sure to also add the appropriate project-level label to this issue (eg gtfs-rt, DLA).

Research Question

Single sentence description: Handle inlining / loopy edge cases correctly while cutting segments. shapely.project will not give us clean chunks to easily slice up a shape's geometry for these edge cases Add a "super project" function to do it in with more detail (consider prior and subsequent stops while dealing with current stop).

• Epic: Epic - Daskify RT segment speeds #592
• Related to Research Request - Segment-trip speed diagnostics #594 (3) How are routes that inline / loop handled?
• Related to Research Request - aggregate stop-level metrics by segment #663: stop-level metrics incorrectly aggregated because of edge cases.

Detailed description:

• Set up shapes and stops to be comprised of 3 points and draw a vector / arrow from it
  • For a stop of interest, we look to the prior and subsequent stop to get at directionality
  • vectors: vec1.x = (x2-x1) and vec1.y = (y2-y1)...use projected CRS to take difference -- stop vector
  • do the same for vec2 -- shape vector
  • Take dot product: vec1.x*vec2.x + vec1.y*vec2.y
• Dot product
  • +1 / >0: same direction
  • -1 / <0: opposite direction
  • 0 = orthogonal
• retry if it is not positive (0 or negative) after removing these erroneous coords from the shape geom. anticipate we should only retry a couple times.
• loop_utils currently identifies these edge cases, but potentially needs to be expanded because it's looking at a stop being revisited. This might not identify all the possible inlining if it's not revisiting the same stop_id while on the same trip. Expand function to identify our universe of cases.

How will this research be used?

Use this to correctly slice up stop-to-stop segments.

Deliverables:

• Add a script to handle these edge cases for cutting stop segments.
• TODO: check how vehicle positions end up attaching to these correctly cut segments. We might want to tighten the buffer then for these cases.
  • Note: Greg Newmark's paper: spatial accuracy. 50m necessary for freeways, but for local roads, something like 20m can grab most of the points (for the select operators he looked at).

[tiffanychu90]

Help from @ian-r-rose!