Crossover adjustment of New Zealand marine gravity data, and comparisons with satellite altimetry and global geopotential models

This paper summarises the crossover adjustment of approximately 90,000-line-km of ship-track gravity observations around New Zealand. The adjustment reduced the standard deviation of the similar to 10(6) crossovers from similar to 2.0 mgal to similar to 0.3 nigal. These data were then used to assess four different grids of satellite-altimeter-derived gravity anomalies. The KMS02 altimeter grid was selected for use around New Zealand as it gave a better fit to the coastal ship-track data. Least-squares collocation was then used to 'drape' the altimetry onto the crossover-adjusted ship-tracks to counter the well-known problems with satellite altimeter data near the coast. The precision of this merged ship-altimeter gravity dataset is estimated to be 3.5 mgal.