Should geospatial sources open with a default projection?

[banesullivan]

The current default projection is None for geospatial sources -- this has a specific meaning (to use image coordinates).

I'm wondering if geospatial sources should be opened with EPSG:3857 by default, as this is intuitive and what most users probably do anyways.

Changing this default will likely have ramifications in downstream packages (I know it will affect RGD and django-large-image at least).

Similarly to #1105, this will improve useability of #1065 but is less critical

[manthey]

Although having a default project would make sense in some contexts, I think this would be surprising in others. From a tile serving endpoint, this makes sense. From an algorithm endpoint, this doesn't (at least, I think many algorithms want to work on a pixel-wise basis and not a projected space basis). Maybe the tile serving endpoints that don't specify a project could default to none for non-geospatial and EPSG:3857 for geospatial, but the pythonic interfaces would stay with none as the default.

[banesullivan]

This makes sense. I need to look into if getTile() takes/supports projection as a keyword argument or could easily support it instead of using self.projection.

Perhaps for geospatial sources (at the class-level), getTile() would have a default projection='EPSG:3857' keyword argument while still opening with projection=None by default

[manthey]

I think we currently open different projections as different sources (unlike with styles), so there isn't a getTile parameter.

[banesullivan]

Hm, then this might be too much effort to handle at this time

[manthey]

Based on some discussion, one approach would be to have a default projection of some keyword like __default__, for geospatial sources this would be EPSG:3857 and for other sources this would be None.

[banesullivan]

I think this makes the most sense. After all, I think it is rare for the rasterio (and even GDAL) sources to be used without a projection.

[banesullivan]

For example, the difference in something as seeminly inconspicuous as getThumbnail() -- having a projection or not is significant:

import large_image
src = large_image.open(path)
src.getThumbnail()[0]

versus with a projection

import large_image
src = large_image.open(path, projection='EPSG:3857')
src.getThumbnail()[0]

No projection	EPSG:3857