Date Austria

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Plaque on the Habsburgwarte on Hermannskogel

The Datum Austria reference system forms the geodetic basis of a map representation of the earth's surface optimized for Austria (see also geodetic date ). In Austria it is also referred to as the usage system , country coordinate system , MGI (this is the official abbreviation), MGI ( Ferro ) or AT_MGI . The OGP EPSG Code (i.e. the code of the European Petroleum Survey Group Geodesy ) for the date Austria is 4805.

The reference system is based on the triangulation of the Military Geographic Institute  (MGI), which laid the foundations of the modern surveying network for the entire territory of Austria-Hungary around 1900 .

Requirements

The MGI reference system mainly includes the following specifications:

use

The date Austria is based on e.g. As the Austrian Federal signaling network  (BMN) and the ÖAMTC - road maps at a scale of 1: 150,000 ( Ed Hölzel. , Vienna). Further information on the history of the Austrian map reference systems can also be found in "Photogrammetric Engineering & Remote Sensing", March 2004.

history

With the independence of the individual nation states after the First World War , the MGI date was retained in Austria despite its peripheral location , in order not to have to change the coordinates of all survey points and millions of border points . The neighboring states to the east, however, went over to other fundamental points that were more central to their national territory .

Conversions

To coordinates that are z. For example, if you refer to the global WGS84 or European ETRS89 datum, to convert to coordinates in Datum Austria (and vice versa), a coordinate transformation is required.

Helmert transformation

The Helmert transformation is usually used for a distortion- free transformation between different reference systems . The following table lists the seven parameters of a Helmert transformation from the WGS84 or ETRS89 to the date Austria:

Starting system Target system c x (meters) c y (meters) c z (meters) s ( ppm ) r x ( arcsecond or new second ) r y ( arcsecond or new second ) r z ( arc second or new second )
WGS84 Date Austria −577.326 −90.129 −463.919 −2.4232 5.1366 "and
15.8537 cc, respectively 		1.4742 "or
4.5500 cc 		5.2970 "and
16.3489 cc, respectively

With the Helmert transformation of WGS84 GPS data it should be noted that the parameters for distortion (s) and rotation (c x , c y , c z ) from the measurements of the Federal Office for Metrology and Surveying  (BEV) are included in the of the AGREF ( Austrian Geodetic Reference Frame ) project are not or only to a limited extent suitable for uncorrected GPS receivers and software.

When using the Helmert transformation with the parameters of the BEV, an accuracy of an average of 1.5 m across Austria can be expected. A Helmert transformation cannot simply be reduced to a pure x, y, z shift.

Molodensky transformation

Alternatively, the three-parameter Molodenski transformation or a simple x, y, z shift can also be used.

In common GPS receivers , the following values ​​are used for the Molodenski transformation of the WGS84 to the date Austria. The value ΔA relates to the difference in axial lengths from the WGS84 to the Bessel 1841 ellipsoid and the value ΔF to the difference in flattening :

Starting system Target system Brand / product designation c x (m) c y (m) c z (m) ΔA (m) ΔF (x10 4 )
WGS84 Date Austria Garmin Austria NS 596 87 473 738 0.1003748
Magellan , others User 577.3 90.1 493.9 739.845 0.10037483

Program cs2cs

The program cs2cs, which is part of the PROJ.4 library, is suitable for converting coordinates that refer to the date Austria into other coordinate and reference systems and vice versa.

The EPSG codes for Austria are:

As an example, the conversion of Gauß-Krüger coordinates based on the date Austria from a cadastral plan in eastern Austria ( Irenental ) into geographical longitude and latitude based on WGS84: 

       cs2cs +init=epsg:31256 +to +init=epsg:4326

In EPSG: 31256 the Helmert parameters are defined, which are given in the above table in the GPS line. You can also specify the parameters yourself. Depending on the number of parameters (3 or 7), the program decides which transformation (Molodenski or Helmert) is to be used. The command line is then: 

       cs2cs +proj=tmerc +ellps=bessel +lon_0=16.33333333333333 +x_0=0 +y_0=-5000000 \
                         +towgs84=577.326,90.129,463.919,5.137,1.474,5.297,2.4232 +units=m \
             +to +proj=longlat +ellps=WGS84 +datum=WGS84

See also

Web links