This study investigates the quality (in terms of elevation accuracy and systematic errors) of three recent publicly available elevation model datasets over Australia: (i) the 9 arc second national GEODATA DEM-9S ver3 from Geoscience Australia and the Australian National University; (ii) the 3 arc second SRTM ver4.1 from CGIAR-CSI; and (iii) the 1 arc second ASTER-GDEM ver1 from NASA/METI. The main features of these datasets are reported from a geodetic point of view. Comparison at about 1 billion locations identifies artefacts (e.g. residual cloud patterns and stripe effects) in ASTER. For DEM-9S, the comparisons against the space-collected SRTM and ASTER models demonstrate that signal omission (due to the ∼270 m spacing) may cause errors of the order of 100–200 m in some rugged areas of Australia. Based on a set of geodetic ground control points over Western Australia, the vertical accuracy of DEM-9S is ∼9 m, SRTM ∼6 m and ASTER ∼15 m. However, these values vary as a function of the terrain type and shape. Thus, CGIAR-CSI SRTM ver4.1 may represent a viable alternative to DEM-9S for some applications. While ASTER GDEM has an unprecedented horizontal resolution of ∼30 m, systematic errors present in this research-grade version of the ASTER GDEM ver1 will impede its immediate use for some applications.

Satellite radar altimeter‐derived sea surface heights (SSH) are in error in coastal regions due, in part, to the complex nature of echoes returned from rapidly varying land and sea surfaces. This paper presents improved altimeter‐derived SSH results in Australian coastal regions using the waveform retracking technique, which reprocesses the waveform data through a “coastal retracking system”. The system, based upon a systematic analysis of satellite radar altimeter waveforms around Australia, improves SSH data from several retrackers depending on the waveforms' characteristics. Central to the system is the use of two techniques: the least squares fitting and the threshold retracking algorithms. To overcome the problem of fading noise, the fitting algorithm has been developed to include a weighted iterative scheme. The retrackers include five fitting models and the threshold method with varying threshold levels. A waveform classification procedure has also been developed, which enables the waveforms to be sorted and then retracked by an appropriate retracker. Two cycles of 20‐Hz waveform data from ERS‐2 have been reprocessed using this system to obtain the improved SSH estimates. Using the AUSGeoid98 gravimetric geoid model as a quasi‐independent reference, the system improves SSH estimates from beyond ∼22 km to beyond ∼5 km from the coastline.

Summary. A ‘gravity anomaly’ is essentially the difference between the gravitational acceleration caused by the Earth's masses and that generated by some refer