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J. Wickert, N. Jakowski: GNSS Based Sounding of the Atmosphere/Ionosphere 127
corresponding Rayleigh wave has passed the region
(JAKOWSKI et al., 2006).
GPS altimetry and reflectometry/scatterometry
In analogy and parallel to the atmospheric refraction
another error source for the most geodetic applications,
multi-path effects, can be effectively used as measurement
signal for GPS based altimetry and scatterometry/reflectometry.
Initial results at GFZ on the basis of ground based
measurements indicate an accuracy of ~2 cm for the
monitoring of lake surface height variations (HELM et al.,
2006a,b; 2005). GNSS reflection measurements (ground
and also space based, see, e.g., BEYERLE et al., 2002) are
currently regarded as potential data source for various
applications in geoscience and atmospheric research.
Detailed data analysis can reveal information on ice surface
properties (roughness), ice coverage of oceans, sea surface
heights, significant wave height and wind speed/direction
above sea surfaces. The reflected signals also contain
information on the propagated atmosphere/ionosphere (e.g.
integrated electron content along the ray paths).
Summary and Outlook
GNSS based atmosphere/ionosphere sounding can be
regarded as an established remote sensing technique. It will
further benefit from increasing densities of global and
regional ground networks and an increasing number of LEO
satellites. Further progress with respect to spatial and
temporal coverage of the GNSS measurements can be
reached by the future use of the signals from GALILEO
and GLONASS. The continuation of the current scientific
investigations will increase the spectrum and the capability
of GNSS based atmospheric/ionospheric remote sensing.
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