Low-Cost GNSS and Real-Time PPP: Assessing the Precision of the u-blox ZED-F9P for Kinematic Monitoring Applications

• Published in: Remote sensing (Basel, Switzerland) Switzerland), 2022-10, Vol.14 (20), p.5100
• Main Authors: Hohensinn, Roland, Stauffer, Raphael, Glaner, Marcus Franz, Herrera Pinzón, Iván Darío, Vuadens, Elie, Rossi, Yara, Clinton, John, Rothacher, Markus
• Format: Article
• Language: English
• Subjects: Accuracy; Ambiguity; Antennas; Arm; Densification; Earthquakes; Equipment costs; Global navigation satellite system; GNSS instrumentation; Ionosphere; Kinematics; Low cost; low-cost GNSS; Monitoring; Open source software; PPP-AR; precision and accuracy; Quality assessment; Real time; real-time kinematic PPP; Receivers & amplifiers; Remote sensing; Robot arms; Satellites; Seismic activity; Seismology; Software; Stability analysis; Static tests; strong-motion seismology; Warning systems; Weight reduction
• ISSN: 2072-4292; 2072-4292
• DOI: 10.3390/rs14205100

With the availability of low-cost, mass-market dual-frequency GNSS (Global Navigation Satellite System) receivers, standalone processing methods such as Precise Point Positioning (PPP) are no longer restricted to geodetic-grade GNSS equipment only. However, with cheaper equipment, data quality is expected to degrade. This same principle also affects low-cost GNSS antennas, which usually suffer from poorer multipath mitigation and higher antenna noise compared to their geodetic-grade counterparts. This work assesses the quality of a particular piece of low-cost GNSS equipment for real-time PPP and high-rate dynamic monitoring applications, such as strong-motion seismology. We assembled the u-blox ZED-F9P chip in a small and light-weight data logger. With observational data from static experiments—which are processed under kinematic conditions—we assess the precision and stability of the displacement estimates. We tested the impact of different multi-band antenna types, including geodetic medium-grade helical-type (JAVAD GrAnt-G3T), as well as a low-cost helical (Ardusimple AS-ANT2B-CAL) and a patch-type (u-blox ANN-MB) antenna. Besides static tests for the assessment of displacement precision, strong-motion dynamic ground movements are simulated with a robot arm. For cross-validation, we collected measurements with a JAVAD SIGMA G3T geodetic-grade receiver. In terms of precision, we cross-compare the results of three different dual-frequency, real-time PPP solutions: (1) an ambiguity-float solution using the Centre National d’Études Spatiales (CNES) open-source software, (2) an ambiguity-float and an AR (ambiguity-resolved) solution using the raPPPid software from TU Vienna, and (3) and a PPP-RTK solution using the u-blox PointPerfect positioning service. We show that, even with low-cost GNSS equipment, it is possible to obtain a precision of one centimeter. We conclude that these devices provide an excellent basis for the densification of existing GNSS monitoring networks, as needed for strong-motion seismology and earthquake-early-warning.