Last week, the CTA opened up its Train Tracker API code so outside developers can applications using it.
That's great news. Developers have used the Bus Tracker API to build a number of apps for smartphones and other uses.
But what interested me in the announcement was the explanation of how Train Tracker works.
From the Train Tracker developer site:
How train data gets into our system
Information in the CTA Train Tracker beta comes from data fed to CTA from its rail infrastructure (unlike buses, our current railcar fleet does not have GPS hardware). This data is then processed by software we use to monitor our rail system which also generates the predictions for train arrivals based on recent train travel times from one point to another. (The software is a product called QuicTrak, made by QEI, Inc.)
Prediction data are combined with other data and polished to help present information in the most meaningful way possible.
What the API does
The API makes it easy for developers to get specific, machine-readable information from CTA Train Tracker to incorporate estimated arrivals and location information into innovative apps--mobile, online, or at locations.
Now compare the above explanation with this one given in the press release to announce the launch of Train Tracker in January:
Estimated arrival times are generated through a combination of
scheduling information and data collected by the software that monitors
the signal system to indicate when a portion of track is occupied by a
train. CTA Train Tracker calculates estimated arrival times by first
measuring how long it takes a train to travel a portion of track and
then averaging the times of the last five trains to move across a
portion of track.
The latter makes more sense to me, the layman. You developer geeks get cool geek-speak.