[Proj] Projection Dev - How to call other projections fromaprojection?

[Noel Zinn (cc)]

Thanks.  Please clarify what you mean by "implementing"?  You're looking for 
the Proj.4 commands that will pull this off?  Or you're coding this as an 
additional projection in your instance of Proj.4?  Or you are coding this 
projection in some language other than Python independent of Proj.4 and 
thought the members of this forum could offer some guidance.  Pardon me if 
I've missed the obvious.  -Noel

Noel Zinn, Principal, Hydrometronics LLC
+1-832-539-1472 (office), +1-281-221-0051 (cell)
noel.zinn at hydrometronics.com (email)
http://www.hydrometronics.com (website)

-----Original Message----- 
From: Michael Speth
Sent: Sunday, October 09, 2011 6:56 PM
To: PROJ.4 and general Projections Discussions
Subject: Re: [Proj] Projection Dev - How to call other projections 
fromaprojection?

I meant ellipsoid and sphere; I apologize for confusing those terms.

I am trying to implement the HEALPix projection from a python
implementation from one of our team members.  The python version has
methods for projecting onto an ellipsoid as well as a sphere.  The
python version's forward and inverse ellipsoid functions call the
forward and inverse sphere functions.

We will also be implementing a new projection called an rHEALPix which
is documented here:
http://code.scenzgrid.org/index.php/p/scenzgrid-py/source/tree/master/docs/scenzgrid_math.pdf

Thank you for your help!

On 10/10/11 12:43, Noel Zinn (cc) wrote:
> "Spheroid" and "ellipsoid" are synonyms for the same thing in geodesy and
> cartography.  See:
>
> http://en.wikipedia.org/wiki/Spheroid
>
> Do you mean that you have an ellipsoid and a sphere, maybe a conformal
> sphere intermediate between the ellipsoid and the plane?
>
> What "new" projection are you implementing?  Does it have a name or is it
> something you invented?  Is it conformal?
>
> Noel Zinn, Principal, Hydrometronics LLC
> +1-832-539-1472 (office), +1-281-221-0051 (cell)
> noel.zinn at hydrometronics.com (email)
> http://www.hydrometronics.com (website)
>
> -----Original Message-----
> From: Michael Speth
> Sent: Sunday, October 09, 2011 4:06 PM
> To: proj at lists.maptools.org
> Subject: [Proj] Projection Dev - How to call other projections from
> aprojection?
>
> Greetings,
>     I am working on implementing a new projection and stumped on how to
> call a projection from within a projection.
>
> For example, the projection has both a spheroid and ellipsoid.  The
> function for determine the projection of the ellipsoid (both forward and
> inverse) use their respective spheroid projections during calculation.
> Unfortunately, I'm not sure if the ENTRY function can be used because
> for the ellipsoid calculation, but the spheroid function is only an
> intermediate step int the calculation and there exists additional
> computations after the spheroid function is called.
>
> Consider this example:
>
> INVERSE(e_inverse);
>      lp = INVERSE(p_inverse);
>      lp.phi = auth_lat(...);
>      return lp;
>
> Does this make sense?  If so, is there any way of calling the inverse
> function for sphere within the inverse function for ellipsoid?
>
> Thank you for your help
> Michael Speth
> Landcare Research
> Scientific Programmer
>
>
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