[OSRS-PROJ] Horrors of --- Krovak projection

[Ron Russell]

Gerald I. Evenden wrote:
> 
> This is just a short note on the status of the Krovak projection.
> 
> The forward projection appears to be working in its native
> math-based mode.  Tests for conformality with the -V option
> show it is OK.  Math-correct x-y are in the -x -y quadrant
> for Czech geographic coordinates.
> 
> Currently the execution script looks like:
> 
> <S-JTSK> +proj=kocc +ellps=bessel +czech
>      +lon_0=24d50 +lat_0=49d30
>      +lat_t=59d42'42.69689 +lat_1=78d30 +k_0=.9999
> 
> To generate Czech grid system values the flag option +czech
> must be used to shift math-x to Y and math-y to X, changing
> the sign to positive in Czech area.  That is plus y west of
> Helsinki and plus x south of Helsinki.
> 
> Another factor to resolve is the longitude used by the Czechs.
> Test values of FORTRAN and C code examples us Greenwich PM
> data but one example obviously must use another meridian---
> perhaps the Ferro one.  The above script is set for
> Greenwich.
> 
> Lastly, the inverse has to be added but once we have a
> good forward, this should not take as much time.
> 
> If anyone is interested in the math I would be glad to
> email a pdf file---about 26k in .gz or 50+k in uncompressed
> form.  As far as I know, this is now the defining math
> for the Krovak in English.  Please ask for a copy, review
> it and let me know of any deficiencies.
> 
> For hassles in using the Krovak in Grass, I suggest they
> use the native math form with false eastings and northings
> to get positive first quadrant values and not mess with the
> code.
> 
> Lastly, I tried to make the basic projection modifiable for
> general applications.  Some simplifications in the cod were
> made so that future mods may be required for true generality.
> If I had included the total math there would have been a few
> more + options to worry about.
> 
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Gerald,

Can I please have a copy of the pdf file. The zipped version
is fine.

Ron
-- 


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Ron Russell
Senior Software Engineer, Laser-Scan Ltd
+44(0)1223 420414

http://www.laser-scan.com

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