Dual frequency receiver
In geodesy, two-frequency receivers are special receivers for GNSS satellite systems (GPS, GLONASS , Galileo) which can analyze the radio signals arriving from the navigation satellites on both coded frequencies (L1 and L2). The measuring principle is - beyond the normal pseudoranging (only L1) - the phase measurement of the carrier waves.
Because the refraction in the ionosphere is somewhat dependent on the frequency, its influence can be estimated from the difference between the two distance measurements (see also quasi-difference ). It is usually a few meters, but can sometimes reach 50 meters due to unusual solar activity .
The first two-frequency receivers (around 1990) weighed around 10 kg, were difficult to operate and cost as much as a small car. Today's devices are much lighter - the antenna is placed on the tripod instead of the reflector, the control unit can be attached next to it (see web links). Most devices can also work in RTK ( real time kinematic ) mode and achieve an accuracy of 1 to 2 cm. GPS modules that can receive both channels (L1 and L2) now cost less than € 100.
In 2018, a chipset from Broadcom BCM47755 came on the market that supports two frequencies (L1 + L5) and can also be used in cell phones. In Xiaomi MI8 this chipset is used.
See also: Precise Point Positioning and RTK (Real Time Kinematic) measurement
Literature and web links
- Günter Seeber : Satellite Geodesy. Basics, methods and Applications . de Gruyter-Verlag, Berlin et al. 1989, ISBN 3-11-010082-7 , (English edition: Satellite geodesy. Foundations, Methods, and Applications . 2nd completely revised and extended edition. Walter de Gruyter, New York NY 2003, ISBN 3-11-017549-5 ).
- Heribert Kahmen : Applied Geodesy. Surveying . 20th completely revised edition. de Gruyter, Berlin et al. 2006, ISBN 3-11-018464-8 , ( de Gruyter textbook ), Section 16: Land surveying .
- Geodetic GNSS receivers, GeoDIS ( Memento from February 26, 2011 in the Internet Archive )
- Single- and dual-frequency receivers from Leica, GX 1210-1220-1230 series ( Memento from April 20, 2004 in the Internet Archive )
- Sources of error in GPS (with image for ionospheric correction)
Individual evidence
- ↑ Xiaomi Mi 8 review | GPS GALILEO accuracy | Dual frequency smartphone. August 6, 2018, accessed December 7, 2019 (German).