Larson et al.: Using GNSS Signals to Measure Water Levels in ITRF
traveled by the reflected signal. As shown in Fig. 1, the frequency of the interfer-
ence pattern is linearly related to the vertical height of the GNSS antenna phase
center above the water surface, and thus relative sea level. The area over which
the reflections occur is also directly related to the height of the GNSS antenna
and the elevation angle of the satellite.
Although the initial studies of GNSS-IR took advantage of existing GNSS in-
struments, there is no reason that an inexpensive GNSS instrument (such as the
one in your cell phone) could not be used in an analogous fashion. Several stud-
ies have shown the value of using these cheaper units (Strandberg and Haas 2019,
Williams et al. 2020). Here we will describe the basic principles of GNSS-IR and
summarize its accuracy. We will also share access to open source software that
has been developed to analyze GNSS data for this purpose (Larson 2022).
References
Larson, K.M. (2022): gnssrefl software description, https://github.com/kristinemlarson/
gnssrefl, accessed 04/2022.
Larson, K.M., Ray, R.D., Nievinski, E.G., Freymueller, J. (2013): The Accidental Tide
Gauge, In: IEEE Geosci. Rem. Sens. Lett., Vol. 10(5). 1200-1205. DOI: 10.1109/
LGRS.2012.2236075.
Larson, K.M., Ray, R.D., Williams, S.P. (2017): A ten year comparison of water levels
measured with a geodetic GPS receiver versus a traditional tide gauge. In: J. Atmos.
Ocean Tech., Vol. 34(2). 295-305. DOI: 10.1175/J7TECH-D-16-0101.1.
Strandberg, J., Haas, R. (2019): Can we measure sea level with a tablet computer, GPS
Solut., 23:61. DOI: 10.1109/LGRS.2019.2957545.
Williams S. D. P., Bell, P. S., McCann, D.L., Cooke, R., Sams, C. (2020): Demonstrating the
potential of low-cost GPS units for the remote measurement of tides and water levels
using interferometric reflectometry. In: J. Atmos. Ocean Tech. Vol. 37(10). 1925-1935.
DOI: 10.1175/T TECH-D-20-0063.s1.
Kontakt
Prof. Emerita Kristine Larson
Universität Bonn
Nußallee 17, 53315 Bonn
klarson@uni-bonn.de
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