[PROJ] Pitching the proj project to Google's Geo team

[Martin Desruisseaux]

Le 20/08/2022 à 23:40, Cameron Shorter via PROJ a écrit :

> I now have a job at Google (outside of Geospatial), and have been 
> asked to present to Google's Geo team about misaligned maps due to 
> tectonic plate movements, and what to do about that.
>
I did not answered directly to the first question yet, but are you aware 
of OGC GGXF effort?

    https://github.com/opengeospatial/CRS-Gridded-Geodetic-data-eXchange-Format/

This is a proposed OGC standard format for encoding the information 
needed for performing coordinate transformations due to tectonic plate 
movements, among other geodetic operations. It is currently based on 
netCDF, but we try to split the standard in a "carrier neutral" core and 
an annex which applies the core to netCDF-4 carrier. That way, it keeps 
the door open for adding other carriers (e.g. ZARR or GeoTIFF) if needed.

A little bit of history: ESRI and IOGP (the maintainer of EPSG database) 
started to look at this issue maybe 5~10 years ago. ESRI already made a 
first proposal based on netCDF at that time (so contrarily to what have 
been said on this mailing list, this effort did not started because of 
PROJ doing something similar 2 years ago). However that work had little 
progress until 2 years ago for human resource reason: CRS activity in 
the last years at OGC has progressed a lot thanks to a man who 
accomplished a tremendous amount of standardization work: Roger Lott 
from IOGP. But Roger has been busy with the first version of ISO 19162 
(WKT 2) before 2015, then with revision of ISO 19111 precisely for 
taking in account plate movements (that ISO 19111 revision introduced 
dynamic CRS and "Point Motion" operation), then with revision of ISO 
19162 for leveraging above-cited new capabilities, and revision of EPSG 
database schema (version 10.x changed significantly compared to 9.x) for 
same reason. Roger became available for new work only 2 years ago.

The GGXF working group includes members from IOGP, ESRI, AIG 
(International Association of Geodesy), various mapping agencies and 
Chris Crook who helped to design the GeoTIFF format used by PROJ for 
gridded datum shifts. So not only we are well aware of the work PROJ 
initiated, but one of the key designers of that work is one of the most 
active GGXF contributors.

The group has produced two documents. One document about deformation 
model (largely Chris's work) has been completed and will be submitted at 
OGC for approval I think in October. The other document is about the 
GGXF format itself, which after 2 years of work is close to completion. 
The feasibility of GGXF is tested by a prototype written in Python by Chris.

So to address the tectonic movements issue, I think that OGC standards 
are putting pieces in place, thanks to Roger's and Chris's work. I 
presume that when GGXF will be an approved standard, it will be used in 
EPSG database as operation parameters whose value is a path to a GGXF 
file. But there is a delay of many years between standard approval and 
their actual implementation in open source software. For example in 
Apache SIS, we have not yet implemented the new features introduced in 
ISO 19111:2019 (point motion operations, etc.) and the corresponding 
updates in ISO 19162:2019 and EPSG database version 10.x. In PROJ as 
well, I'm not sure if "Point Motion operation" is already implemented.

So I believe that OGC standards are in good progress for addressing the 
issue raised by Cameron, but implementations lag a few years behind 
(which is normal).

     Martin

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