[OSRS-PROJ] Radius parameters

[Black, Jerry]

Hi,

I hope this is not too off-topic... I'm using the proj4 library in my own
application (on a win95 pc), and while it appears to work relatively well,
I'm limited by my lack of understanding.

In particular, I don't understand the significance of the Radius Parameters
as described in Evenden's reports. While the effect of choosing a given
radius parameter is documented (e.g. R_A), what I'm lacking the rational for
choosing one of these parameters (or not), when choosing a given projection.


Is the choice merely up to the user (and therefore likely selected on some
particular minimization of distortion), or are there well-known common
practices (e.g. for a MERC projection of the Cdn east coast always use R_A).

Thanks in advance,

Jerry Black	(902) 426-2950
Invertebrate Fisheries Division /  Marine Fish Division
Bedford Institute of Oceanography
P.O. Box 1006,  1 Challenger Drive
Dartmouth, NS   Canada    B2Y 4A2		
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