[OSRS-PROJ] Goode projection discrepancy

[Gerald I. Evenden]

The seam between Sinusoidal and Mollweide is where the scales are equal
I suppose the 40:44:11.8 is a little more accurate than the 40:44 that the
original sources from Snyder but who cares.  The typical scale of Goode
is so small that 11.8" ain't goin to make much difference!

The Y correction is because the two projections do not produce the same
y value at 40:44.  Equitorial-Polar aspect varies between
pseudocylindricals.

Beware, there are at least two versions of Goode's interuptions.  Also,
there are
gores that duplicate regions.  Almost impossible to make an automatic
version.
Take a look at one of Goode's atlases.

Interrupted projections are a nightmare to automate!

__________________________________________________
Jerry Evenden and the Low Riders, Katie and  Daisy May
gevenden at capecod.net  http://www.capecod.net/~gevenden
----- Original Message -----
From: Morten Hulden <morten at ngb.se>
To: <osrs-proj at remotesensing.org>
Sent: Wednesday, October 04, 2000 2:52 PM
Subject: [OSRS-PROJ] Goode projection discrepancy


>
> Can anyone explain why PROJ in the Goode projection uses a different
> latitude breakpoint for switching from Sinusoidal to Mollweide projection.
> Other sources (e.g.  http://edcdaac.usgs.gov/1KM/goodesarticle.html ,
> http://edcftp.cr.usgs.gov/pub/software/misc/gihll2ls.c ) have the
> breakpoint at 40 44' 11.8 degrees (0.71098798993 rad).
>
> The PROJ function uses 0.71093078197902358062 (exactly 40 44'
> degrees), but then adds/substracts a correction term (Y_COR) to the
> output.
>
> Is the result the same? My limited math mind suggests it's not, though the
> difference may not be significant on global maps.
>
> I noted this when I was looking at implementing interrupted goode
> homolosine in PROJ. Interrupted or not, the breakpoint should be at 40
> 44' 11.8, no?
>
> Morten Hulden
    ...

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