[PROJ] Sndyer Map Projections Manual in HTML form

[Mircea Neacsu]

Thanks for taking the time to check it out. I see it mostly as a 
preservation work, not as a starting point. That is why my JS 
"implementation" adheres as much as possible to Synder's original 
formulas, without any clever tricks or optimizations. The library of 
Congress preserves Snyder's TI-59 calculator 
<https://blogs.loc.gov/maps/2015/11/saving-early-computer-cartography/> 
and magnetic strips.


Mircea Neacsu
M: 514-591-0329
E:mircea at neacsu.net

On 4/5/2024 10:33 AM, Charles Karney wrote:
> I have mixed feelings about your enterprise.  Undoubtedly, Snyder (1987)
> is an invaluable resource and it was the foundation for Gerald Evenden's
> implementation of PROJ.  However, time marches on, and, while it remains
> a useful reference work, it's probably not the best place to start when
> implementing new code.  A few examples:
>
> * most of the series used by Snyder are in the eccentricity, e.  In
>    nearly every case the corresponding series in the third eccentricity,
>    n, converges faster.  In particular, this is the case for all the
>    conversions between auxiliary latitudes.
>
> * many of his expressions for conformal projection express the integral
>    of sec(phi) as log(tan(pi/4 + phi/2)).  For computational purposes,
>    asinh(tan(phi)) is preferred (more accuracy near the equator and poles
>    and transparently odd).
>
> * he uses a terrible series for the transverse Mercator projection.
>
>    --Charles
>
> On Sat, Mar 30, 2024 at 7:01 PM Mircea Neacsu via PROJ
> <proj at lists.osgeo.org>  wrote:
>> Hello,
>>
>>
>>
>> My work of converting Snyder – Map Projection Manual to HTML is almost finished. Probably the most interesting part are the numerical examples, implemented using JavaScript. All formulas can be recalculated, and one can see all the intermediate steps and the result of those calculations.
>>
>>
>>
>> I would very much like to hear your comments. Given the number of formulas, I’m sure there are many errors that have slipped through, and I will be grateful if you will point those out.
>>
>>
>>
>> Thank you,
>>
>> --
>>
>>
>>
>> Mircea Neacsu
>>
>>
>>
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>
>
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