Airborne geoid mapping of land and sea areas of East Malaysia

Abstract

This paper describes the development of a new geoid-based vertical datum from airborne gravity data, by the Department of Survey and Mapping Malaysia, on land and in the South China Sea out of the coast of East Malaysia region, covering an area of about 610,000 square kilometres. More than 107,000 km flight line of airborne gravity data over land and marine areas of East Malaysia has been combined to provide a seamless land-to-sea gravity field coverage; with an estimated accuracy of better than 2.0 mGal. The iMAR-IMU processed gravity anomaly data has been used during a 2014-2016 airborne survey to extend a composite gravity solution across a number of minor gaps on selected lines, using a draping technique. The geoid computations were all done with the GRAVSOFT suite of programs from DTU-Space. EGM2008 augmented with GOCE spherical harmonic model has been used to spherical harmonic degree N = 720. The gravimetric geoid first was tied at one tide-gauge (in Kota Kinabalu, KK2019) to produce a fitted geoid, my_geoid2017_fit_kk. The fitted geoid was offset from the gravimetric geoid by +0.852 m, based on the comparison at the tide-gauge benchmark KK2019. Consequently, orthometric height at the six other tide gauge stations was computed fromand GPS-levelling heights (H GPS Lev ) at the six tide gauge locations indicate RMS height difference of 2.6 cm. The final gravimetric geoid was fitted to the seven tide gauge stations and is known as my_geoid2017_fit_east. The accuracy of the gravimetric geoid is estimated to be better than 5 cm across most of East Malaysia land and marine areas.

A high-precision digital astrogeodetic traverse in an area of steep geoid gradients close to the coast of Perth, Western Australia

“…6, the advantage of the astronomical method becomes clear: While only local data along the traverse is needed to compute the astronomical solution, the numerical integration in two coordinate directions requires gravity data outside our study area. The degradation of the marine gravity data is the prime suspect for the tilts in the quasigeoid models, adding yet more evidence that airborne gravimetry should be used to bridge this deficiency (e.g., Schwarz and Li 1996, Li et al 2016, Jamil et al 2017. AGQG2017 uses an integration cap of 55 km, so the extents of Fig.…”

The New Zealand gravimetric quasigeoid model 2017 that incorporates nationwide airborne gravimetry

“…Airborne gravimetry provides such data coverage over otherwise inaccessible areas (coastal areas and in rough topography). Airborne gravity has been shown to be suitable for regional geoid computations (e.g., Schwarz and Li 1996, Bastos et al 1997, Kearsley et al 1998, Forsberg et al 2000, Novaìk et al 2003, Olesen 2003, Sjöberg and Eshagh 2009, Hájková 2011 and has been used extensively for this purpose over the past 10 years (e.g., in Mongolia (Forsberg et al 2007), Taiwan (Hwang et al 2007), South Korea (Bae et al 2012, Yang 2013, Jekeli et al 2013, Nepal (Forsberg et al 2014), East Malaysia (Jamil et al 2017), Antarctica (Scheinert et al 2008) and the US GRAV-D project (Smith et al 2013;Li et al 2016;Wang et al 2017)). For these reasons, airborne gravimetry appears well suited to account for the shortcomings of the existing gravity data in NZ to improve the gravimetric quasigeoid model.…”

Semi-kinematic geodetic reference frame based on the ITRF2014 for Malaysia

“…It enables measurements of elevations with respect to a consistent seamless vertical datum everywhere across the country using GNSS positioning. A precise seamless land-to-sea gravimetric geoid model has been determined for Malaysia primarily from airborne gravity data (Jamil H. et al, 2017 andDSMM, 2020). Airborne gravity data processing was referenced to ITRF2008 and ITRF2014, while the gravimetric geoid was computed on a grid of 1.5x1.5 arc-minute (corresponding to a roughly 2.7 km grid) and referenced to GRS80 ellipsoid.…”