How to understand MTA's real-time gtfs data feeds

Question

So far I've filled out the MTA online registration form for a Developer's API Key. Then in my android project, I implemented the gtfs realtime bindings dependecy from one of Google's github repositories,

compile group: 'com.google.transit', name: 'gtfs-realtime-bindings', version: '0.0.4'

Using their Java class, I tried this following code to print out all the gtfs data from the link given by MTA,

try {
    String urlString = "http://datamine.mta.info/mta_esi.php?key=insertmykeyhere";
    URL url = new URL(urlString.toString());
    GtfsRealtime.FeedMessage feed = GtfsRealtime.FeedMessage.parseFrom(url.openStream());
    for (GtfsRealtime.FeedEntity entity : feed.getEntityList()) {
        if (entity.hasTripUpdate()) {
            Log.d("stuff", entity.getTripUpdate().toString());
        } 
    }

} catch (IOException e) {
            e.printStackTrace();
}

However, I'm now having trouble interpreting the data printed out. I understand that there are static data feeds from http://web.mta.info/developers/developer-data-terms.html, which I used to interpret some of the data. Here is one of the trip updates printed out,

stuff: trip {
    trip_id: "036000_GS.N01R"
    start_date: "20170218"
    route_id: "GS"
    1001: "\n\0200S 0600  GCS/TSS\020\001\030\001"
}     
stop_time_update {
    departure {
        time: 1487415600
    }
    stop_id: "901N"
    1001: "\n\0011\022\0011"
}
stop_time_update {
    arrival {
        time: 1487415690
    }
    stop_id: "902N"
    1001: "\n\0011"
}

I understand some parts such as trip_id, start_date, and stop_id. But parts such as trip_id, time, and 1001 I'm still unsure about it and the text files from the static feed don't do the best job of explaining them.

Answer 1

The MTA Subway GTFS-RT feeds are a little different than most others.

Typically, GTFS-RT refers directly back to a static GTFS' via trip_id/stop_id/etc. Since in NYC there is usually a deviation from normal service ("2 Train via the 5 Line"), the RT feed retains the option to create new trips that do not exist in the static feed.

To answer your immediate questions, you need to add the realtime extensions. That should solve the empty 1001: field.

To do so, either compile the proto file, or just import the onebusaway-gtfs-realtime-api library, which has the extensions pre-compiled in:

    ExtensionRegistry registry = ExtensionRegistry.newInstance();
    registry.add(GtfsRealtimeNYCT.nyctFeedHeader);
    registry.add(GtfsRealtimeNYCT.nyctStopTimeUpdate);
    registry.add(GtfsRealtimeNYCT.nyctTripDescriptor);

   GtfsRealtime.FeedMessage feed = GtfsRealtime.FeedMessage.parseFrom(url.openStream(), registry);

This gives a result like:

trip {
  trip_id: "B20170217WKD_132800B..S"
  start_date: "2017-02-17 22:08:00"
  route_id: "B"
  [transit_realtime.nyct_trip_descriptor] {
    train_id: "1B 2208 145/BBC"
    is_assigned: true
    direction: SOUTH
  }
}
stop_time_update {
  arrival {
    time: 1487390920
  }
  departure {
    time: 1487390920
  }
  stop_id: "D39"
  schedule_relationship: SCHEDULED
  [transit_realtime.nyct_stop_time_update] {
    scheduled_track: "A3"
    actual_track: "A3"
  }
}
stop_time_update {
  arrival {
    time: 1487391130
  }
  departure {
    time: 1487391130
  }
  stop_id: "D40"
  schedule_relationship: SCHEDULED
  [transit_realtime.nyct_stop_time_update] {
    scheduled_track: "A3"
    actual_track: "A3"
  }
}