[PROJ] "eck_greif" projection, "libproject"?

[Even Rouault]

Nyall,

> 
> Does anyone know what the "+proj=eck_greif" mentioned in section 7.2.1
> of http://priede.bf.lu.lv/ftp/pub/TIS/bibliotekas/PROJ.4/libproj4_manual.pdf
> refers to? I can't find any reference to this in master proj code base at
> all. (It's also referenced here:
> https://github.com/Esri/projection-engine-db-doc/blob/master/other/proj4-esr
> i.txt#L154, which is why I'm asking the question)
> 
> The proj4-esri.txt file also states:
> 
> "Names marked with a * are only in the libproject distribution
> Names marked with a @ are only in the PROJ4      distribution"
> (https://github.com/Esri/projection-engine-db-doc/blob/master/other/proj4-es
> ri.txt#L21)
> 
> Does anyone have any clues as to what "libproject distribution" is? I
> can't find anything relevant from my searching, but given the context
> it sounds like some historic proj fork?

This is likely the libproj4, that was forked from PROJ4 in 2002 by Jerry 
Evenden when he disagreed with the project directions :
http://libproj4.maptools.org/

Particularly the lbp4_050319S.tar.gz source archive. Unfortunately I can't 
find any mention of eck_greif into it.

There's also the
https://github.com/jeffbaumes/jeffbaumes-vtk/tree/master/Utilities/vtklibproj4 
sources that Kristian identified in 
https://github.com/OSGeo/PROJ/issues/1851#issuecomment-574878542 but no trace 
of eck_greif into it

The most promising would be to start from
https://www.javatips.net/api/onebusaway-jmapprojlib-master/src/main/java/com/
jhlabs/map/proj/EckertGreifendorffProjection.java

whose header indicates "This file was semi-automatically converted from the 
public-domain USGS PROJ source.
 * 
 * Bernhard Jenny, May 07: split Hammer and Eckert-Greifendorff projections."

So, with that hint, looking in PROJ src/projections/hammer.cpp, the projection 
name is  "Hammer & Eckert-Greifendorff"

And when comparing hammer.cpp with EckertGreifendorffProjection.java, it seems  
Eckert-Greifendorff is actually just "+proj=hammer +W=0.25 +m=1"

End of treasure hunt :-)

(but there must another libproj4 or whatever variant name archive somewhere!)

Even

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