Geodetic reference point
GPS receivers enable us to determine our exact position on the Earth's surface, for example as a navigation aid, for positioning photos and videos, for locating cell phones, or for geocaching.
The city of Mainz offers a precisely defined geodetic reference point for checking your GPS device.
Set your GPS device to the WGS84 reference system and compare your measurements with the coordinates of the geodetic reference point.
The reference point is located on the Rathausbrücke (between the town hall and the bridge tower) and has the following coordinates:
Geographical coordinates:
Longitude: 08° 16' 31.918''
Latitude: 50° 00' 01.989''
UTM coordinates:
East value (E): Zone 32 U 448080.38
North value (N): 5538943.58
Normal height:
91.78 m above sea level
Geographical coordinates
Geographical coordinates describe a location on the Earth's surface using two angles in degrees and minutes. One degree has 60 minutes, one minute has 60 seconds. The lines of longitude converge at the poles, so one minute of longitude in the north corresponds to a shorter distance than in the south. One minute of longitude corresponds to approximately 1190 m in Mainz, one minute of latitude to approximately 1834 m.
Official coordinate reference system ETRS89
The ETRS89 (European Terrestrial Reference System 1989) refers to the stable European continental plate. This means that ETRS89 coordinates remain permanently the same. This reference system is suitable for precise satellite surveying in the cm range.
System WGS84
Most GPS receivers refer to the globally defined reference system WGS84 (World Geodetic System 1984). The coordinates change by a few centimeters each year due to global continental drift.
For navigation applications with handheld GPS devices, WGS84 and ETRS89 can be considered identical.
Further information on the topic "Reference systems"
What is the procedure for checking?
- Locate the reference point.
- Set the coordinate output of your GNSS/GPS receiver to the specified reference system.
- Place your receiver on the reference point or hold the receiver steady above the point.
- Determine the location coordinates using your device (recommendation: measure for several minutes).
- Compare your measured values with the coordinates of the reference point.
Deviations in the geographic coordinates:
Longitude difference: 0.01" corresponds to approx. 0.20 m.
Latitude difference: 0.01" corresponds to approx. 0.30 m. It
is easier with UTM coordinates, as this is a metric system.
The accuracy depends on the number of available satellites and their position. It is therefore recommended to carry out the check at different times of the day.
UTM coordinates
The UTM (Universal Transverse Mercator) system is a global rectangular coordinate system divided into right and high values.
The right value (E = "East") 32U 448080.38 E
32 stands for the central meridian 9°. Zone U lies between 48° and 56° north latitude and thus covers most of Germany. The value 448080.38 is the distance from the central meridian in meters, plus 500,000 m to avoid
negative values west of the central meridian.
The high value (N="North") is the distance of the point from the equator along the central meridian in meters.
Many thanks to Afry (opens in a new tab), who determined the precise coordinates and exact altitude using geodetic measurements.