Although I previously said that matching the current angle of travel to the a nearby road with a similar angle of travel in order to match the current location to road worked just fine, that’s actually incorrect. What happens when the vehicle turns a corner is that the angle of travel does not match either of the roads it’s currently on. For example, if approaching an intersection which looks like a “T” and runs North/South and East/West, then while turning the vehicle is traveling somewhere between North/South and East/West. So the angle of travel doesn’t match either of the possible roads to which one would hope to match the location.
Match GPS Location to Road Data (Attempt 2)
Perhaps one thing that went horribly wrong with the previous attempt was putting more weight (importance) on the current angle of travel instead of the distance to a road segment. Assuming the GPS data isn’t off by too much, then the distance to the nearby road segments should be the most important. i.e. initially there should be a choice between 3 or less road segments based on distance.
Ideally, a path of travel would be saved and matched to nearby road segments, so that if the vehicle travels North then turns West, we could match to road segments which travel North and then West. Unfortunately I don’t have any ideas on how to implement this. It seems difficult because the GPS data gives you a lot more points to work with than the map data, to the point where the GPS data seems continuous compared to the discrete map data.
So next I will snap the GPS’ location to the nearest road segment and test the results. From there I will try to come up with a way to solve issue mentioned in an earlier post where the “snapped-to” road’s angle of travel does not match the current angle of travel at all. Currently I have two ideas: 1) Don’t allow the road to change until the angle more closely matches the new road and 2) detect when near an intersection and (similar to #1) allow the road to change when the angle of movement matches the new road more than the current road. For 1 and 2, if the road looks like a “T” then 45 degrees would be the threshold for changing the road that’s currently “snapped-to.”
Two Weeks Ago
Two weeks ago I worked out various bugs in the methods which remove non-visible lines and do rotations and transformations. The fact that using a “Graphics2D” instance applies things later instead of immediately and the fact that PerspectiveTransform’s can’t be done using a Graphics2D instance caused me to have to rewrite much of the code so that all of the rotations, transformations, etc. could be applied in the correct order.
Last week I augmented the simulation to not only include a GPS location with map data, but to also include the image captured when the GPS data was captured. So now I can test the various algorithms without driving around. From this I noticed that the “snap-to” algorithm works about 10% of the time and needs to improved.