[Proj] Problems with EOV for Hungary (1972 Egyseges OrszagosVetuleti)

[Roger Oberholtzer]

On Tue, 2009-09-22 at 15:19 +0200, OvV_HN wrote:
> ----- Original Message ----- 
> From: "Roger Oberholtzer" <roger at opq.se>
> To: <proj at lists.maptools.org>
> Sent: Tuesday, September 22, 2009 11:02 AM
> Subject: [Proj] Problems with EOV for Hungary (1972 Egyseges 
> OrszagosVetuleti)
> 
> 
> >I am trying to use proj (C API) to project WGS84 lat/longs in EOV for
> > Hungary (1972 Egyseges Orszagos Vetuleti). I am trying to match some
> > user data. The are using ArcGis with the following definition:
> >
> >        PROJCS["HD_1972_Egyseges_Orszagos_Vetuleti",
> >        GEOGCS["GCS_Hungarian_1972",
> >        DATUM["D_Hungarian_1972",
> >        SPHEROID["GRS_1967",6378160,298.247167427]],
> >        PRIMEM["Greenwich",0],
> >        UNIT["Degree",0.0174532925199432955]],
> >        PROJECTION["Hotine_Oblique_Mercator_Azimuth_Center"],
> >        PARAMETER["False_Easting",650000],
> >        PARAMETER["False_Northing",200000],
> >        PARAMETER["Scale_Factor",0.99993],
> >        PARAMETER["Azimuth",90],
> >        PARAMETER["Longitude_Of_Center",19.048571778],
> >        PARAMETER["Latitude_Of_Center",47.14439372222],
> >        UNIT["Meter",1]]
> >
> > I have set this up as:
> >
> >   from = pj_init_plus(
> >                "+proj=latlong "
> >                "+ellps=WGS84");
> >
> >   to = pj_init_plus(
> >                "+proj=somerc "
> >                "+lat_0=47.14439372222222 "
> >                "+lon_0=19.04857177777778 "
> >                "+k=0.99993 "
> >                "+x_0=650000 "
> >                "+y_0=200000 "
> >                "+ellps=GRS67 "
> >                "+units=m "
> >                "+no_defs");
> >
> >     pj_transform(to, from, 1, 0, &le, &ln, &la);
> >
> > When I run some test data, I am always 80 some meters away. For example:
> >
> >   Ref:    Latitude:   47.7656110000 Longitude:   18.9532900000
> >   Ref:    Easting:       642942.000 Northing:       269097.700
> >   Calc:   Easting:       642857.473 Northing:       269067.872
> 
> 
> By the way, a Hotine_Oblique_Mercator_Azimuth_Center is not the same as 
> somerc, the Swiss oblique Mercator projection. But, somerc is a better 
> approximation for EOV than a Hotine omerc.
> 
> Anyhow, with the datum transformation parameters from Mikael Rittri and a 
> coordinate frame rotation, I got with:
> Ref:    Latitude:   47.7656110000 Longitude:   18.9532900000
> a latitude, longitude of 47.765881, 18.954420
> and with an accurate implementation of the EOV projection an (original axes) 
> x, y of:
> 269097.773, 642942.210
> which is, let's say, spot on.
> The approximation with somerc should give (its) x, y of:
> 642942.210, 269097.775

This looks promising. So, I have now tried:

   from = pj_init_plus(
       "+proj=latlong "
       "+ellps=WGS84");

   to = pj_init_plus(
       "+proj=somerc "
       "+lat_0=47.14439372222222 "
       "+lon_0=19.04857177777778 "
       "+k=0.99993 "
       "+x_0=650000 "
       "+y_0=200000 "
       "+ellps=GRS67 "
       "+units=m "
       "+towgs84=52.684,-71.194,-13.975,-0.312,-0.1063,-0.3729,1.0191 "
       "+no_defs");

     pj_transform(to, from, 1, 0, &le, &ln, &la);

And I see no difference at all. I use +towgs84 elsewhere, so I know it
works like this. But, as I said, I see no difference.

-- 
Roger Oberholtzer

OPQ Systems / Ramböll RST

Ramböll Sverige AB
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