[PROJ] package 'geosphere' -- transforming spherical-based geographic coordinates to WGS84

[Even Rouault]

Douglas,

> Can someone show me what I'm doing wrong, or misunderstanding?

Your "+proj=longlat +ellps=sphere +no_defs" string doesn't contain any datum "qualifier", so 
PROJ doesn't attempt to do any change of coordinate. This is a behaviour that has existed 
since PROJ 4.6 if I remember well, and that has been kept during PROJ 6 overhaul.
If you add +towgs84=0,0,0, you will see a change in latitude values.

$ echo "2 49" | cs2cs +proj=longlat +ellps=sphere +to +init=epsg:4326
2dE	49dN 0.000

$ echo "2 49" | src/cs2cs +proj=longlat +ellps=sphere  +towgs84=0,0,0 +to +init=epsg:4326
2dE	49d11'25.117"N 0.000


The details of the transformations can also be shown with PROJ >= 6 with:

$ projinfo -s "+proj=longlat +ellps=sphere +type=crs" -t EPSG:4326 -o PROJ
Candidate operations found: 1
-------------------------------------
Operation No. 1:

unknown id, Ballpark geographic offset from unknown to WGS 84, unknown accuracy, World, 
has ballpark transformation

PROJ string:
+proj=axisswap +order=2,1


vs

$ projinfo -s "+proj=longlat +ellps=sphere +towgs84=0,0,0 +type=crs" -t EPSG:4326 -o PROJ
Candidate operations found: 1
-------------------------------------
Operation No. 1:

unknown id, Transformation from unknown to WGS84, unknown accuracy, unknown domain 
of validity

PROJ string:
+proj=pipeline +step +proj=unitconvert +xy_in=deg +xy_out=rad +step +proj=push +v_3 
+step +proj=cart +ellps=sphere +step +inv +proj=cart +ellps=WGS84 +step +proj=pop +v_3 
+step +proj=unitconvert +xy_in=rad +xy_out=deg +step +proj=axisswap +order=2,1



Even

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