[Proj] Re: Hungarian grid

[Paul Kelly]

Hello Gabor,
(Cc to PROJ list)

On Tue, 1 Jun 2004, [ISO-8859-2] Bertók Gábor wrote:

> Dear Paul,
>
> Maybe you remember our request posted approx. a month ago in
> connection with the addition of the Hungarian national grid
> to the list of available projections in the proj module of
> GRASS.

Yes, thank you for reminding me. There didn't seem to be anything 
obvious for me to do so I put it to one side and then forgot about it with 
the pressures of other work. Sorry. Anyway what the document appeared to 
have was a list of parameters for the Hotine Oblique Mercator, which 
shouldn't be overly complicated to implement in PROJ.4 or GRASS if you 
work through the PROJ documentation (see http://proj.maptools.org/ ).

I have copied the English section from the pdf file you sent me below; 
perhaps someone on the PROJ list will be able to help you with formulating 
the projection in PROJ.4 format but it should not be too difficult. Maybe 
you can provide the full Hungarian PDF file if anyone needs it; it is a 
bit big (170kB) to send on the mailing list.

If you think any modifications to GRASS are necessary (e.g. you have datum 
transformation parameters that can be added), don't hesitate to ask again 
on the GRASS developers' mailing list.

Paul


High accuracy Hotine Oblique Mercator
approximation of the Hungarian EOV
coordinates
G. Molnr G. Timr
Summary
The precise Hungarian Datum 1972 (HD72;geodetic coordinates)---Hungarian
EOV coordinate transformation is a special oblique Mercator projection:
its normal parallel slightly but intentionally differs from the parallel
of the central point of the projection.However,the HD72--EOV
transformation can be approximated with high precision by defining
appropriate values of a standard Hotine Oblique Mercator projection.The
maximum horizontal error of the approaching projection is 0.17
millimeters in Hungary.This enables the definition of the Hungarian EOV
projection in worldwide used GIS software packages,and even for
precision-claiming geodetic applications.The parameters are the
following:
Latitude of the central point:
F 0 =47 08'39.8174";
Longitude of the central point:
. c =19 02'54.8584";
Scale factor:
k_0 =0.99993;
Azimuth of the central line at the central point:
a =90 ;
False Northings:
y_0 =200000.00114 m;
False Eastings:
x_0 =-9370549.28432 m.