International Global Navigation Satellite Systems Association
IGNSS Symposium 2018
Colombo Theatres, Kensington Campus, UNSW Australia
7 – 9 February 2018
Combination of GNSS and InSAR for Future
Australian Datums
Thomas Fuhrmann
Geoscience Australia, Canberra, Australia
Phone: +61 2 6249 9187, email: thomas.fuhrmann@ga.gov.au
Matthew Garthwaite
Geoscience Australia, Canberra, Australia
Sarah Lawrie
Geoscience Australia, Canberra, Australia
Nicholas Brown
Geoscience Australia, Canberra, Australia
ABSTRACT
GNSS can provide a temporally dense set of geodetic coordinate
observations in three dimensions at a small number of discrete measurement
points on the ground. Compare this to the Interferometric Synthetic Aperture
Radar (InSAR) technique which gives a spatially dense set of geodetic
observations of ground surface movement in the viewing geometry of the
satellite platform, but with a temporal sampling limited to the orbital revisit
of the satellite. Using both of these methods together can leverage the
advantages of each to derive more accurate, validated surface displacement
estimates with both high temporal and spatial resolution. In this paper, the
properties of both techniques are discussed with a view to combined usage
for future Australian datums. Differential GNSS processing is applied to data
observed at a local geodetic network in the Sydney region as well as time
series InSAR analysis of Radarsat-2 data. Surface displacements resulting
from the two techniques are compared and validated at 21 geodetic
monitoring sites equipped with GNSS and radar corner reflectors (CRs). The
resulting GNSS/InSAR displacement time series agree at the level of 5 to 10
mm. This case study shows that the co-located GNSS/CR sites are well-
suited to compare and combine GNSS and InSAR measurements. An
investigation of potential multipath effects introduced by the CRs attached
directly to GNSS monumentation found that daily site coordinates are
affected at a level below 0.1 mm. The GNSS/CR sites may hence serve as a
local tie for future incorporation of InSAR into national datums.
KEYWORDS: GNSS, GPS, InSAR, Combination, Datums, Surface
Displacements, Geodetic Networks
