On Wed, Mar 5, 2014 at 12:08 PM, Moritz Lennert <[email protected]> wrote: > Hello, > > Recent discussions here with colleagues about GRASS' vector format and the > teaching of vector handling in GIS have brought up a question about the fact > that GRASS (contrary to some other well-known vector formats) allows a mix > of geometry types (points, lines, polygons) in the same map, something which > some GIS'ers consider quite unorthodox.
Nothing to add to Ben's reply from a user perspective. >From a conceptual perspective, it depends on the definition of "vector map". Considering the number of vector formats (76 supported by OGR), any definition must be independent of a specific vector format. In OGR, a vector is defined as a data source which contains any number of layers which in turn contain vector geometry objects. A vector geometry object in turn can be a collection of vector geometry objects of possibly different types. This property of a geometry object and geometry collection conforms to the OGC simple feature specification, a software and vector format independent (!) standard. That means that even a single geometry object in a single layer in a single data source can contain multiple feature types. In my experience, a common task (probably the most common task) is to convert GIS data of any format to the format of your choice. Thus I would be surprised if regular GIS users are not familiar with the diversity you find out there in the wild. Markus M > > In order to enrich the reflection on that, I would like to ask GRASS users > for use cases where this mix has been useful. Do you use such mixed geometry > maps ? Which specific use cases do you use them for ? > > In order not to flood the mailing list, you can also send me your response > by private mail. I'll report back to the mailing list with the results. > > Moritz > _______________________________________________ > grass-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/grass-user _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
