[PROJ] PROJ grid files CDN

[Clifford J Mugnier]

Speaking of grids ... NGS has officially released GEOID18 this week for CONUS.


Clifford J. Mugnier, c.p., c.m.s.

Chief of Geodesy

LSU Center for GeoInformatics (ERAD 266)

Dept. of Civil Engineering (P.F. Taylor 3531)

LOUISIANA STATE UNIVERSITY

Baton Rouge, LA  70803

Academic: (225) 578-8536

Research: (225) 578-4578

Cell:             (225) 328-8975

honorary lifetime member, lsps

fellow emeritus, asprs

member, apsg

________________________________
From: PROJ <proj-bounces at lists.osgeo.org> on behalf of Even Rouault <even.rouault at spatialys.com>
Sent: Friday, September 13, 2019 4:24 PM
To: proj at lists.osgeo.org <proj at lists.osgeo.org>
Subject: Re: [PROJ] PROJ grid files CDN

> I think I'll be in roughly the same situation as QGIS developers. Have you
> and Howard considered grids-on-demand as a PROJ API that developers could
> use in QGIS or Rasterio or gdalwarp? Or as a service like DNS? Something
> about having it built into the library feels not right to me.

I have imagined that the network layer could be an interface, with a default
libcurl implementation, that applications/libraries could subsitute with their
own.
As some grids can be pretty big and we don't necessarily want to download them
in their entirety, that could be something like
DownloadRange(url, start_offset, length)
One use case where this solution is kind of compulsory is if you have to do
coordinate reprojection in a context like AWS Lambda with a very small
footprint for the application.

> I'm trying to
> think of a precedent for this and am drawing a blank.

On your phone, you have the Maps app, but this is just the app: the map
content is stored remotely, and you have to connect if the area of interest is
not in the cache.

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