Satellite positioning service of the German national survey
The satellite positioning service of the German land survey ( SAPOS ) is a satellite reference service . As a joint project of the Working Group of Surveying Administrations of the Federal Republic of Germany (AdV), it provides correction data with which a more precise position determination is possible in Germany using satellites .
The basis of this service is a network of permanently operated GNSS - reference stations (formerly known as "permanent stations" hereinafter). With over 270 stations, all of Germany is covered. SAPOS provides correction data for positioning and navigation with the satellites of the Global Positioning System (GPS) and GLONASS .
The SAPOS reference stations are operated by the federal states and can be used uniformly nationwide. They replace the necessary second receiver for differential GNSS measurements, so that the user only needs a single one. The data from the reference stations are fed to the user and enable the position accuracy to be increased by 10 to 100 times.
The SAPOS reference stations complement the land- marketed fixed points of the national survey and form the basis for numerous measurements in the ETRS89 reference system . With the help of transformations , the computational transition from this reference system to classic national reference systems can be realized.
For equipped and authorized users, SAPOS offers three different levels of accuracy for use in real time or for subsequent calculations. SAPOS comprises three service areas with different properties and levels of accuracy:
|abbreviation||Surname||Procedure||Positional accuracy||Height accuracy|
|EPS||Real-time positioning service||RTK||0.3 to 0.8 m||0.5 to 1.5 m|
|HEPS||Real-time, high-precision positioning service||RTK||1 to 2 cm||2 to 3 cm|
|GPPS||Post-processing geodetic positioning service||Post processing||under 1 cm||1 to 2 cm|
The transmission of correction data in the standardized correction data format RTCM 2.3 for the EPS service takes place with the NTRIP protocol, previously via radio. HEPS works with the correction data format RTCM 2.3 or 3.0. The transmission takes place with Ntrip or GSM . The GPPS data is made available in RINEX format; the responsible bodies have set up special download areas for this.
Reference station networks with a structure similar to that of the SAPOS network have been installed in almost all European countries as well as in Japan and the USA in recent years. SAPOS was seen as a technical role model.
As part of public-private partnerships, SAPOS provides the commercial correction data services ascos (since 2002) and VRSNow from Trimble (2006–2008), as well as Smartnet from Leica (since 2011), data from its reference stations for further processing in accordance with the contracts.
Due to the possibility of medium and long-term evaluation of the data recorded by the highly accurate stations, there is also scientific interest in the position data of the reference stations, e.g. B. to determine recent crust movements or earthquake research. Other analyzes focus on the water vapor content of the earth's atmosphere (meteorology) or the number of free charges ( TEC ) in the ionosphere .
- ^ AdV working group of the German surveying administrations: Services at a glance. Accessed October 9, 2019 (German).