I've done a lot of testing of "distanceToDestination" (D2D) and "offCourseDistance" (OCD) Activity Info metrics. My goal is to track progress along a route and estimate finish time based on analytics of ride performance. It works great.
I'm also testing a way to detect OFF COURSE to alert the rider and to inform my analytics. A few observations and a solution that seems to be as good as we can get.
1. Garmin has "Off Course" logic built in and throws up a message. But we don't have access to that, unfortunately. Another (intentional?) gap in access to features from CIQ, like GRADE and others. Ugh.
2. Even when precisely on top of the loaded route, CIQ's "off course" (OCD) distance can be 1000 meters or more, when the map view shows me on top of the route. So that alone isn't a reliable indicator. This isn't a GPS issue, my "dot" is tracking on the route. It is OCD being confused when another sector of the route is close by possibly. But D2D is doing the right thing so it also knows I'm on the correct part of the route. Weird.
3. Distance to Destination (D2D) seems to work well while you are actually on the route, decrementing at the same rate as Distance Traveled (DT) is incrementing. If you are on the route but going in the wrong direction, D2D increases at the rate of Distance Traveled. GREAT. However, if you are off course, then D2D seems to still change if you are heading in the general direction of the destination, like it now acts as a "as the crow flies" distance. So you can't trust D2D not changing if you are off route either.
So, my current logic is to flag you as Off Course if EITHER (*or*) of these conditions are true. Since Garmin doesn't want to give is their internal Off Course flag.
- D2D is fixed or increasing (this is a reliable indication by itself - if while you are moving, it isn't changing or you are moving away from the destination)
- OCD > X *and* (change in DT - change in D2D) > Y (if the change in D2D is nearly identical to the change in DT then you are most likely on route, then ignore the possibly bad OCD metric)
