Add documentation around adding projection/raster extension to collection for summaries/item assets

[m-mohr]

I'd like to add the projection extension to a collection. Specifically, I've added proj:espg to the summaries and I basically want to get the projection extension entry into stac_extensions.

I've tried ProjectionExtension.ext(collection, add_if_missing=True), but it returns a

pystac.errors.ExtensionTypeError: Projection extension does not apply to type 'Collection'

I don't think this is true. Proj can be used in Collection summaries for sure.

[m-mohr]

Same applies for raster in item asset definitions

[gadomski]

I can't reproduce. I ran this file at pystac v1.6.1, and no errors were raised:

from pystac import Collection, Extent, SpatialExtent, TemporalExtent
from pystac.extensions.projection import ProjectionExtension
from pystac.extensions.raster import RasterExtension

collection = Collection(
    "an-id",
    "a description",
    Extent(
        SpatialExtent([-106.0, 41.0, -105.0, 42.0]),
        TemporalExtent.from_now(),
    ),
)
ProjectionExtension.add_to(collection)
RasterExtension.add_to(collection)
assert (
    "https://stac-extensions.github.io/projection/v1.0.0/schema.json"
    in collection.stac_extensions
)
assert (
    "https://stac-extensions.github.io/raster/v1.1.0/schema.json"
    in collection.stac_extensions
)

Please re-open if I'm misundstanding.

[m-mohr]

I don't have a working Python environment right now, but the code above says ProjectionExtension.ext(collection, add_if_missing=True), not ProjectionExtension.add_to(collection). Did you try the code above or just yours?

[gadomski]

Ah, I misunderstood. Is this more of what you were trying to do?

from pystac import Collection, Extent, SpatialExtent, TemporalExtent
from pystac.extensions.projection import ProjectionExtension

collection = Collection(
    "an-id",
    "a description",
    Extent(
        SpatialExtent([-106.0, 41.0, -105.0, 42.0]),
        TemporalExtent.from_now(),
    ),
)
proj = ProjectionExtension.summaries(collection, add_if_missing=True)
assert (
    "https://stac-extensions.github.io/projection/v1.1.0/schema.json"
    in collection.stac_extensions
)
proj.epsg = [4326]
collection_as_dict = collection.to_dict()
assert collection_as_dict["summaries"]["proj:epsg"] == [4326]

[m-mohr]

Yes, although I used ProjectionExtension.ext(collection, add_if_missing=True) instead of ProjectionExtension.summaries(collection, add_if_missing=True) as I was not aware of the summaries method. I found it now at https://pystac.readthedocs.io/en/stable/api/extensions/projection.html?highlight=.summaries#pystac.extensions.projection.ProjectionExtension.summaries but that's pretty hidden and may need some additional documentation, no?