intuit stop ID for vehicles that dont report them

[hamima-halim]

fairly regularly (5000ish times maybe), we will get gps pings from vehicles that reporting their route information, but not their upcoming stop. here's a map of ~2000 such pings over the course of a day https://www.google.com/maps/d/u/0/edit?mid=1ttstvWGxhXTY62ZOA7YYQr-o3Srnbj8&usp=sharing

we currently ignore these pings, which does give us decent headway calculations but can produce holes in our records. as far as i can tell, theres 3 types of stop id outages we tend to see

1. short stretch outages, which occur for less than a minute and tend to happen at the beginning/end of the stop. these are short enough that we could probably ignore them and have reasonable calculations, even if they happen in the middle of a trip.
2. medium stretch outages, which occur for maybe 2-10 minutes at a time. we see these a lot on the 39 (potentially caused by a glitchy AVL) and they can cause us to lose information for a couple of stops.
3. long stretch outages, which might be because the AVL for a vehicle wasn't turned on but GPS was still reporting info.

if a vehicle has been dark for more than ~a minute, we should start trying to interpolate its progress along its shape if possible. there will probably be some complexity wrt

• small route diversions
• figuring out the inbound/outbound direction of the trip, if that's null (we might be able to grab this from gtfs? or just use previous ping info)
• how to store shape information in-memory for quick enough calculations without ballooning memory usage (maybe just cache the more problematic route shapes)
• monitoring the duration of a vehicle's outage in order to kick off this calculation
• determining whether an event is an arrival or a departure (or neither.) i havent seen any STOPPED_AT events in these outages, and its unclear if the vehicles actually making any stops and not reporting it.