Bus Plotter IV: Extrapolate From Stop Predictions |
September 26th, 2010 |
| mbta, mbtaplot, programming, python, tech, transport |
I've made the plotter now take advantage of the "predictions"
command offered by the webservice that tells you how many minutes it
will be before a specific bus arrives at a given stop. Instead of
doing linear extrapolation from the previous two reported positions
it uses the previous position and an upcoming stop. I first tried
using the next stop to do predictions, but because the webservice
only provides data at the minute level, this was much too inaccurate
and I switched to using a threshold of two minutes out. There might
be multiple stops two minutes out, so we break ties by taking the
closest one to the last known bus location.
See it in action: mbtaplot