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I'm building a consolidated map of all transit systems in my area in QGIS. I have a GTFS dataset of bus lines, and it includes shapes for every trip on every route in the system (as it should), but that's far more detail than I need, and very slow to render.

I'd like to filter the data to map only the longest possible trip on each route in each direction (inbound/outbound). What's the best way to do this? Line number, route direction, and shape length are all separate columns. I'd prefer to keep the underlying dataset intact if possible.

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You could

  1. use Group Stats plugin to calculate the max length per bus route.
  2. Save the result as CSV
  3. Join the CSV back to the line layer
  4. Select those features/lines where length = max length
  5. Export those to a new dataset
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  • Apparently the dataset has already the shape length already so that step can be avoided
    – Antonio Locandro
    Commented Jun 7, 2014 at 20:37
  • @AntonioLocandro There is no step in my instructions to calculate the length. Using group stats, one can calculate the max value of all lines belonging to a bus route.
    – underdark
    Commented Jun 7, 2014 at 20:38
  • This worked for me. Once I filtered, however, I discovered several routes take multiple paths, so I just selected the missing variants manually and merged them into the reduced set. Thank you!
    – Victoria
    Commented Jun 10, 2014 at 20:49

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