Hydrographic datum and GNSS heighting in the SW Java Sea, Indonesia: Comparison between observed and models of Sea Surface

Abstract

There have been developments of GNSS heighting in hydrography. These are motivated by the need for improving the efficacy of hydrographic operations, through omission of shore-based tidal surveys and post-processed datum reduction of depth soundings. However, this will demand presence of hydrographic separation model (HSM) that defines the vertical relationship of any tidal datum used in hydrography to ellipsoid. In addition to that, a reliable technique for real-time positioning is also required. At the same time, the overall accuracy the use of the entire system (i.e. height datum, vertical positioning) must be identified. This paper discusses the prospect of using models of sea surface for the construction and operation of HSM for the SW Java Sea, Indonesia. The discussion is based on two models of sea surface: the analytically constructed sea surfaces (i.e. HAT, MSL, LAT) according to data from TPXO.7 missions and models of sea surface database published by the Indonesian Agency for Geospatial Information. In order to verify the operability of such models, observation of geodetic heights of instantaneous sea levels across an approximately 13.5 Nm sailing tracks between Pramuka (Seribu Islands) and Ancol (Jakarta) is made. It is evident that the work presented here results in deviation level in the order of several tens of centimetres. This provides reasonably quantified contribution to the error budget against the standard of depth accuracy for data presented on nautical charts as of Zone of Confidence A and hence confirm the prospect of using existing surface models and vertical positioning respectively for the construction and operation of HSM in the domain in question.