The group has been developing and operating a real-time precise GNSS positioning service since 2007, motivated by the use of high-precision GNSS for early warning systems for geohazards. Real-time positioning and navigation is an integral part of today’s society and is used by most people on an everyday basis in smartphones, cars, or sports watches. The main difference of our work are the much higher requirements on the accuracy, integrity, and continuity of the solutions, so that for instance the positioning error should be on the (sub-) centimeter level rather than the meter level as obtained with current mass-market devices.

To this end, we apply a technique called precise-point-positioning (PPP). It is based on precise satellite orbit and clock products as compared to the standard broadcast values which are provided by the system operators, and it makes use of the carrier-phase observations, which are roughly two-orders of magnitude more precise than the conventional code-observations but ambiguous by an unknown number of cycles. The full potential of the carrier-phases can be exploited when fixing these phase ambiguities, known as integerambiguity resolution. Faster convergence times are obtained when providing a user with atmospheric corrections as regional augmentation.

Our positioning service can be used operationally and is employed for geoscientific applications such as earthquake studies. In our research, we focus on multi-GNSS integration, the extension to multiple frequencies, techniques for reliable ambiguity resolution, and the definition, computation and description of the associated PPP corrections.

References

[1] Li X, Ge M, Dai X, Ren X, Fritsche M, Wickert J, Schuh H (2015): Accuracy and reliability of multi-GNSS real-time precise positioning: GPS, GLONASS, BeiDou, and Galileo. Journal of Geodesy, 89(6):607-635. DOI: 10.1007/s00190-015-0802-8

[2] Brack A, Männel B, Schuh H (2021): GLONASS FDMA data for RTK positioning: a five-system analyis. GPS Solutions, 25:9. DOI: 10.1007/s10291-020-01043-5

[3] Brack A, Männel B, Schuh H (2023): Two-epoch centimeter-level PPP-RTK without external atmospheric corrections using best integer-equivariant estimation. GPS Solutions, 27:12. DOI: 10.1007/s10291-022-01341-0

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