Suggestion: add a LineStringField attribute to the Shape class for geo queries

tulsawebdevs / django-multi-gtfs

Django app to import and export General Transit Feed Specification (GTFS)

http://tulsawebdevs.org/

Apache License 2.0

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Suggestion: add a LineStringField attribute to the Shape class for geo queries #18

Closed araichev closed 10 years ago

araichev commented 10 years ago

I'm a newbie to GeoDjango, so please correct me if i'm misunderstanding something.

Would it be a good idea to add a LineStringField attribute to the Shape class in shape.py that encodes the geometry of the shape so that then one could make geometric queries such as "Get me all the trips in bounding box blah"?

araichev commented 10 years ago

For geometric queries, it would also be handy for stop objects to have a 'geometry' attribute (or some name like that) that's a PointField object, trip objects to have a geometry attribute that's a LineStringField object, and route objects to have a geometry attribute that's a MultiLineStringField object, the union of its trip line strings. What do you think?

jwhitlock commented 10 years ago

Working on this feature. Stops and ShapePoints already have a point field. After the changes:

a Shape will have a geometry LineStringField that is the sequence of ShapePoints,
a Trip will have a geometry LineStringField which is the same as the Shape, or is the sequence of Stops through StopTimes,
a Route will have a geometry MultiLineStringField which is the collection of Trip lines

The geometry fields are populated at the end of a GTFS import, and updating the point of a Stop or a ShapePoint will cause a cascading update of related Shapes, Trips, and Routes. We'll see if that is useful and performant.

jwhitlock commented 10 years ago

Cached geometries are included in v0.3.1