Estimating Position from Millisecond Samples of GPS Signals (the “FastFix” Algorithm)

A new approach to GPS positioning is described in which the post-processing of ultra-short sequences of captured GPS signal data can produce an estimate of receiver location. The algorithm, called ‘FastFix’, needs only 2–4 ms of stored L1-band data sampled at ∼16 MHz. The algorithm uses a least-squa...

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Bibliographic Details
Published in:Sensors (Basel, Switzerland) Switzerland), 2020-11, Vol.20 (22), p.6480
Main Author: Molteno, Timothy C. A.
Format: Article
Language:English
Subjects:
Accuracy
Algorithms
Code Division Multiple Access
codephase
Global positioning systems
GNSS
GPS
Letter
Lightweight
navigation
Noise
Patch antennas
Position measurement
Post-production processing
Power management
Propagation
Satellites
Signal processing
wildlife tracking
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Summary:A new approach to GPS positioning is described in which the post-processing of ultra-short sequences of captured GPS signal data can produce an estimate of receiver location. The algorithm, called ‘FastFix’, needs only 2–4 ms of stored L1-band data sampled at ∼16 MHz. The algorithm uses a least-squares optimization to estimate receiver position and GPS time from measurements of the relative codephase, and Doppler-shift of GNSS satellite signals. A practical application of this algorithm is demonstrated in a small, lightweight, low-power tracking tag that periodically wakes-up, records and stores 4 ms of GPS L1-band signal and returns to a low-power state—reducing power requirements by a factor of ∼10,000 compared to typical GPS devices. Stationary device testing shows a median error of 27.7 m with a small patch antenna. Results from deployment of this tag on adult Royal Albatross show excellent performance, demonstrating lightweight, solar-powered, long-term tracking of these remarkable birds. This work was performed on the GPS system; however, the algorithm is applicable to other GNSS systems.
ISSN:1424-8220
1424-8220
DOI:10.3390/s20226480