How to use custom TMS/projection with 'Mosaic from COG urls' example

[Shane98c]

Thanks for such a powerful tool!

I've got the example from here working: https://developmentseed.org/titiler/examples/code/mosaic_from_urls/

It seems fast and great!

My next requirement is to get this working for polar projections. I've been able to add a custom tms to the route like so:

EPSG3031 = TileMatrixSet.custom(
    (-948.75, -543592.47, 5817.41, -3333128.95),
    CRS.from_epsg(3031),
    identifier="EPSG3031",
)

tms = tms.register([EPSG3031])

...

mosaic = MosaicTiler(reader=MultiFilesBackend, path_dependency=DatasetPathParams, supported_tms=tms, default_tms="EPSG3031")

It shows up under /docs and appears to be generally working. However, the output is not changed, and tiles are still returned in web mercator when I hit the endpoint with a request like this:
http://127.0.0.1:8000/tiles/EPSG3031/7/44/93@4x?url=https://pgc-opendata-dems.s3.us-west-2.amazonaws.com/rema/strips/s2s041/2m/s64w056/SETSM_s2s041_WV01_20180922_102001007A2EAF00_102001007D190200_2m_lsf_seg1_dem_10m_shade_masked.tif
(I would expect this request to fail since the zxy are defined for the location in web mercator tms, instead it just returns the tile)

I think this all has to do with using this: from cogeo_mosaic.backends.base import BaseBackend which I've seen in a couple code comments only supports web mercator.

Is there an example someone could point me to which sets up a backend that can mosaic multiple cogs (provided via list in url) like the example above but also supports projection to custom tms (and accepting tile requests in that custom tms as well)

I feel like I might be missing something fundamental in my mental model here. I really appreciate any help!

[vincentsarago]

👋 Hi @Shane98c

😬 This turns out to be pretty complex. The Mosaic Factory use BaseBackend as a reference class. Because in BaseBackend the TMS is set with init=False (meaning that user shouldn't pass the tms as input parameter) the MosaicTilerFactory's tiles endpoint do not use TMS as a reader input

titiler/src/titiler/mosaic/titiler/mosaic/factory.py

Lines 278 to 283 in 418bb93

	with self.reader(
	src_path,
	reader=self.dataset_reader,
	reader_options={**reader_params},
	**backend_params,
	) as src_dst:

This is one of the reason we had to re-write most of the factory for titiler-pgstac https://github.com/stac-utils/titiler-pgstac/blob/master/titiler/pgstac/factory.py#L251-L255

Sadly there is no quick fix (apart re-writing the MosaicTilerFactory tile and tilejson code on your end.

FYI, I wanted to refactor the multiple file example to switch from mosaic to regular BaseReader but didn't find the time to finish. I'll 👋 you if I do

[Shane98c]

Thanks @vincentsarago! Am I correct in understanding that titiler-pgstac has the desired mosaic & projection functionality working already? We're exploring building a dynamic STAC server with pgstac so playing with titiler-pgstac is on my list!

[vincentsarago]

titiler-pgstac has the desired mosaic & projection functionality

Yes it does

@Shane98c feel free to checkout https://github.com/developmentseed/eoAPI for a full pgstac + stac + tiler solution

[vincentsarago]

FYI here is a simple mosaic reader you can use with a simple TilerFactory https://gist.github.com/vincentsarago/d2175fb73c62467b116640c1359fc0bd

Not tested and do not implement all methods

[Shane98c]

Thanks so much @vincentsarago! I'll give it a try!