Clarify projection of bounding box columns

[kylebarron]

Clarify projection of bounding box columns

[jorisvandenbossche]

Yes, I think it would be good to add a sentence to explicitly state that the values in the bbox column should be interpreted in the projection of the corresponding geometry column.

(note this is not necessarily the primary geometry column, as the covering bbox info is in the column metadata, so in theory you can have multiple geometry columns in a file each with a different CRS and have a bbox column for each of those)

[rouault]

Do the bbox columns HAVE to be in the same projection as the data?

There should be a strong use case for allowing bbox columns not to be in the same projection as the data, as that would be a source of complexity. I can't think of any other existing geospatial format that has a a spatial index in a SRS that is not the one of the geometries being indexed.

[cholmes]

I agree there should be a strong use case for bbox columns in a different projection.

It does seem like this could be an area where there's experimentation for awhile before we bring it into the spec. Like there's nothing stopping adding an extra consistent-bbox column in WGS84, or even only using that (since the core bbox one is optional). If there's compelling cases for it we could add it.

Not sure if we need to be more explicit in the spec that for now we require the bounding box geometry to be the same as the specified crs?

[cholmes]

So do we want to say something in the spec, just to be clear that current practice is for bbox columns to be in the same projection as the primary geometry column?