[MapProxy] shift when reprojecting WMS

[Greg Troxel]

Travis Kirstine <traviskirstine at gmail.com> writes:

> We have a fully seeded cache in a Google Maps / EPSG:3857 SRS and offer the
> data up through a WMS with various SRS supported,  MapProxy is handling the
> reprojection.  We've noticed that with our latest upgrade to mapproxy v14.0
> with pyproj 3.0.1 / proj 7.2.1 there is an error with some SRS being
> shifted incorrectly, specifically EPSG:2958 / UTM Zone17 CSRS.  How does
> mapproxy handle the image reprojection - is it using pyproj or some other
> library?

What do you think is happening, and why?
What do you think shoudl be happening?

CSRS is presumably NAD83(CSRSv?).

3857 refers to the WGS84 ensemble, which includes WGS84(TRANSIT) which
is approximately equal to NAD83(1986) and presumably then to NAD83(CSRS)
(the unsuffixed version).

So I'd expect no transform.  Arguably, there should be one, as the
imagery probably ought to be in spherical mercator from WGS84(G2139)
which is distinct from NAD83(CSRSvRECENT).
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