[Proj] Problems with EOV for Hungary (1972 Egyseges OrszagosVetuleti)
OvV_HN
ovv at hetnet.nl
Tue Sep 22 08:19:35 EST 2009
----- 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
Oscar van Vlijmen
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