SSR vs. OSR

The “accuracy in real-time“ problem

Global Navigation Satellite Systems (GNSS) like GPS, Galileo and others enable positioning by determining the range between a satellite and an observer.

The apparent range (pseudo range) results from the observed travelling time of a signal transmitted from a satellite to a receiver multiplied by the speed of light. The travelling time is affected by several error sources, including satellite orbit and clock errors, biases of the satellite and receiver hardware as well as ionospheric and tropospheric effects.
These effects lead to inaccuracies in real-time positioning of about 3 to 8 meters when using the satellite signals only.

GNSS augmentation service providers generate GNSS corrections by continuously monitoring the signals received by reference stations. With such GNSS real-time correction services, the inaccuracies are reduced down to centimeter or even millimeter level.

GNSMART enables the consistent and
seamless estimation of GNSS errors (rigorous solution)
and provides both OSR and SSR corrections.

OSR and SSR – two qualities of corrections

  • Observation Space Representation (OSR)

In conventional Real-Time-Kinematic (RTK) services the lump sum of all these errors is observed by a network of reference stations and provided to the rover as range corrections for each supported combination of satellite, frequency and signal. OSR requires the processing of the same signals on each reference station (homogeneous network) and the support of these signals by the user.

  • State Space Representation (SSR)

A network of reference stations is used to decorrelate and estimate the different GNSS error components (states):

  • Satellite Clocks
  • Satellite Orbits
  • Satellite Signal Biases
  • Ionospheric Delay/Advance
  • Tropospheric Delay

With SSR users can compute GNSS corrections valid for their position. Additionally,
statistical accuracy information can be transmitted to support the rover algorithm.

Scalable services – various applications

OSR corrections are exchanged via duplex communication media since the user needs to transmit its approximate position to the service provider to generate the corrections.

SSR based network-RTK enables the use of simplex communication media (satellite and ground based broadcast) using only a single data stream for all users. Thereby, an SSR service can in principle supply an unlimited number of users at the same time, making it ideally suited for future mass market applications as e.g. autonomous cars or drones.

The structure of SSR allows scalable RTK services with respect to accuracy and with respect to various specific applications in numerous GNSS market segments, including:

Agriculture

Aviation

Location Based Services​

Maritime​

Rail

Road​

Mapping and Surveying​

Agriculture

Aviation

Location Based Services​

Maritime​

Rail

Road​

Mapping and Surveying​

Agriculture

Aviation

Location Based Services​

Maritime​

Rail

Road​

Mapping and Surveying​

Geo++ GmbH
Steinriede 8
30827 Garbsen
Germany
+49 5131 4689 0
+49 5131 4689 99
gnsmart@geopp.de

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