Started 1999, ongoing
Summary
A new technique, devised at De Montfort University, uses satellite-borne radar
altimeters to determine terrain heights and soil-surface moisture on land.
This collaborative program between Curtin and De Montfort Universities
is using these independent satellite altimeter data to correct errors in Australian
digital elevation models, to quantify the effects of these errors on the determination
of the Australian gravity field, and to generate calibrated time-series of soil-surface
moisture over the Australian continent. The results give accuracy estimates to
the increasing number of users of digital elevation models, an improved determination
of the Australian geoid, and create a totally new data set for the environmental
sciences.
Results
Satellite altimeter-derived heights from ERS-1 have been compared with heights defined
by six digital elevation models (DEM) over Ausstralia. These comparisons show that
there are systematic differences
between the altimeter-derived heights and the DEM defined heights. The agreements
with the Australian DEM (which uses more reliable data than the other two models)
are sightly better. Asssuming the altimeter data and Australian DEM are accurate,
this indicates that the global DEMs should not be relied upon too
greatly in this part of the world.
Figure 1. Differences between altimeter-derived
heights and JGP95E DEM heights in northern Queensland
In Figure 1, there are may areas with geographically correlated differences. It
is thought that this is due to the JGP95E DEM being derived from gravity observation
elevations. These elevations do not accurately sample the topographic shape. Typically
the JGP95E DEM heights are underestimated in high-land regions and over-estimated
in low-land regions. This is due to the logisitics of collecting gravity data with
helecopters. Also in Figure 1, there is a north-south line aparent in the
differences. This is due to the JGP95E model mbeign construicted from Australian
data in the west and NIMA data in the east.
References
Hilton, R.D., W.E. Featherstone, P.A.M. Berry, C.P.D Johnston and J.F. Kirby (2002) Comparison of
Digital Elevation Models (DEMs) over Australia and external validation using ERS-1 satellite radar
altimetry, Australian Journal of Earth Sciences (submitted).
PDF preprint
Berry, P A M, Thornton, S R and Featherstone, W E (1998) Accuracy
assessment of altimeter-derived orthometric heights using regional
digital elevation models, paper presented to European Geophysical
Society General Meeting, Vienna, Austria, April.
Berry, P A M, Thornton, S R and Featherstone, W E (1998) Validation
of altimeter-derived orthometric heights over Australia, paper
presented to British Group of Altimeter Specialists Conference,
Liverpool, England, April.
Berry P A M, Sanders R F, Leenmans C, Bron E (1998) Generating orthometric
heights from the ERS-1 altimeter geodetic mission dataset: results from an expert
systems approach, in: Forsberg R, Feissl M, Deitrich R (eds) Geodesy on the
Move, Springer, Berlin, Germany, 113-118.
Berry P A M, Bron E, Sanders R F, Leenmans C (1998) Use of ERS-1 land
altimetry to validate the GLOBE global digital elevation model, in: Forsberg R,
Feissl M, Deitrich R (eds) Geodesy on the Move, Springer, Berlin, Germany,
119-124.
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