Fwd: [Proj4j] Aitoff projection

[Martin Davis]

fowarded to list


---------- Forwarded message ----------
From: Martin Davis <mtnclimb at gmail.com>
Date: Sun, Jun 6, 2010 at 8:40 PM
Subject: Re: [Proj4j] Aitoff projection
To: Fred Pospeschil <f.w.pospeschil.t.r at charter.net>


Er - not 100% sure til I port it!  I'll have a crack at doing that soon...

On Sun, Jun 6, 2010 at 7:58 PM, Fred Pospeschil
<f.w.pospeschil.t.r at charter.net> wrote:
> So what does the below listed PROJ4 code look like in java?
> From: Martin Davis
> Sent: Sunday, June 06, 2010 6:52 PM
> To: Fred Pospeschil
> Subject: Re: [Proj4j] Aitoff projection
> I'd vote for making the code identical to PROJ4:
>
> if (pj_param(P->params, "tlat_1").i)
>         {
> if ((P->cosphi1 = cos(pj_param(P->params, "rlat_1").f)) == 0.)
> E_ERROR(-22)
>         }
> else /* 50d28' or acos(2/pi) */
> P->cosphi1 = 0.636619772367581343;
>
>
> (I have no idea about the logic behind this code - which is why I'm
> not suggesting changing it!)
>
> M
>
> On Sun, Jun 6, 2010 at 6:40 AM, Fred Pospeschil
> <f.w.pospeschil.t.r at charter.net> wrote:
>> Martin,
>>
>> Jerry's initialization code has the following code:
>>
>>  public void initialize() {
>>   super.initialize();
>>   if (winkel) {
>> //FIXME
>> //   if (pj_param(P->params, "tlat_1").i)
>> //    if ((cosphi1 = Math.cos(pj_param(P->params, "rlat_1").f)) == 0.)
>> //     throw new IllegalArgumentException("-22")
>> //   else /* 50d28' or acos(2/pi) */
>>     cosphi1 = 0.636619772367581343;
>>   }
>>  }
>>
>> Based on my reading of the Proj4 manuals I changed it to read:
>>
>>  public void initialize() {
>>   super.initialize();
>>   if (winkel) {
>> /*
>> Winkel Tripel is the arithmetic mean of the Aitoff and
>> Equidistant Cylindrical projections with the latter’s phi_ts
>> (latitude of true scale) becoming phi_1. If lat_1=phi_1 is
>> not specified, Winkel’s value ofphi _1 = cos-1(2/pi) or
>> 50 27 35. is used. For Bartholomew’s variant, use lat_1=40.
>> Proj4 Manual pg 17 fwp
>>  */
>>     cosphi1 = Math.cos(projectionLatitude);
>>   }
>>  }
>> In addition, I added :
>>
>> projectionLatitude = 0.0;
>>
>> to the constructor.
>>
>> With these changes the code appears to generate graticules/maps which
>> match
>> those in Synders Album.
>>
>> How  do these changes look to you?
>>
>> Fred
>>
>>
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>>