[mapserver-dev] RFC 126: Port to PROJ 6 API

[Even Rouault]

On lundi 7 octobre 2019 16:17:52 CEST Seth G wrote:
> One last question - will it still be possible to use inline projection
> parameters as in the examples at
> https://mapserver.org/mapfile/projection.html#projections-with-mapserver ?

Yes. This is used extensively in msautotest

> If so would this avoid a call to proj.db?

This will save one call, but not all calls. This will save the call for the 
projectionObj instanciation. But as soon as coordinate transformations are 
involved, the DB will generally be accessed. For example if transforming 
between "+proj=longlat +datum=WGS84" and "+proj=longlat +datum=NAD83", the 
EPSG database contains transformations between both datums

$ projinfo -s  "+proj=longlat +datum=WGS84 +type=crs" -t "+proj=longlat 
+datum=NAD83 +type=crs" --summary
Candidate operations found: 53
unknown id, axis order change (2D) + Inverse of NAD83 to WGS 84 (1) + axis 
order change (2D), 4 m, North America - Canada and USA (CONUS, Alaska 
mainland)
unknown id, axis order change (2D) + Inverse of NAD83 to WGS 84 (3) + axis 
order change (2D), 4 m, USA - Hawaii - main islands
unknown id, axis order change (2D) + Inverse of NAD83 to WGS 84 (18) + axis 
order change (2D), 1 m, USA - Florida
unknown id, axis order change (2D) + Inverse of NAD83 to WGS 84 (2) + axis 
order change (2D), 8 m, USA - Alaska - Aleutian Islands
unknown id, axis order change (2D) + Inverse of NAD83 to WGS 84 (41) + axis 
order change (2D), 1 m, USA - Oregon and Washington
unknown id, axis order change (2D) + Inverse of NAD83 to WGS 84 (42) + axis 
order change (2D), 1 m, USA - Wisconsin
[ ... truncated ... ]


Even
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