[Octave-patch-tracker] [patch #9958] [octave forge](mapping) gcxgc

[Philip Nienhuis]

Update of patch #9958 (project octave):

                Category:                    None => Forge : new function   
                  Status:                    None => Need Info              
             Assigned to:                    None => philipnienhuis         

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Follow-up Comment #1:

Thanks for this contribution. Same guy as patch #9492, patch #9634, ... ?

Function looks good, just minor style issues, but many BIST tests, good!

I checked with Matlab, and I want you to review the used formulas. With your
function:

>> [a, b] = gcxgc (20, -5, 45, 30, 5, 15)
a =
  -28.062   28.062
b =
     0   180


while Matlab gives:

a =
   28.0620  -28.0620
b =
    4.4121 -175.5879


AFAICS the culprit is something in L.119 and up where a comment suggests
"Causes ambiguity" and an if statement screws up the otherwise correct
answer.

Also, I see no checks for identical great circle inputs (should return NaNs,
cf. the on-line Matlab help text). As far as my own spherical trig proficiency
goes (warning: rusty because long time ago!) this could be a simple comparison
of the poles of the great circles. Perhaps / probably the answer is already in
one of the intermediate results in your function.

Thanks

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