Abstract
Nearshore bathymetric data are used in many coastal monitoring applications, but acquisition conditions can be challenging. Shipborne surveys are prone to the risk of grounding in shallow waters, and scheduled airborne surveys often fail to coincide with optimal atmospheric and water conditions. As an alternative, since its launch in 2018, ICESat-2 satellite laser profile altimetry data provide free and readily available data on a 91-day repeat cycle, which may contain incidental bathymetric returns when suitable environmental conditions prevail. In this paper, the vertical accuracy of extracted, refraction-adjusted ICESat-2 nearshore marine bathymetric data is evaluated at four test sites in a Northern hemisphere, temperate latitude location. Multiple ICEsat-2 bathymetric values that occurred in close horizontal proximity to one another were averaged at a spatial scale of 1 m and compared with Multibeam Echosounder bathymetric survey data and Global Navigation Satellite System reference data. Mean absolute errors of less than 0.15 m were observed up to depths of 5 m, with errors of less than 0.24 m (to 6 m), 0.39 m (to 7 m) and 0.52 m (to 10 m). The occurrence of larger bathymetric errors with depth, which increase to 0.54 m at maximum photon depths of 11 m, appears to be primarily related to reduced numbers of geolocated photons with depth. The accuracies achieved up to 6 m suggest that the manual extraction, refraction adjustment and bathymetric filtering steps were effective. Overall, the results suggest that ICESat-2 bathymetric data accuracy may be sufficient to be considered for use in nearshore coastal monitoring applications where shipborne and airborne bathymetric data might otherwise be applied.
Highlights
IntroductionPublisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
With regard to the principal aims stated at the outset of this paper, the primary results may be briefly summarised as follows: Firstly, relatively small ICESat-2 marine bathymetric errors of up to 0.15 m were observed to depths of 5 m, with errors of 0.25 m being noted up to depths of 6 m and 0.54 m up to depths of 11 m
The primary aims of this study were to evaluate the potential performance of ICESat-2 marine bathymetric data in a mid-latitude temperate context, determining if accuracies varied by depth, and reporting the ICESat-2 bathymetric data processing chain that was implemented in a manner that could be repeated in the future
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Accurate nearshore bathymetric data are required in many coastal monitoring applications. Nearshore airborne bathymetric surveying is often challenged by environmental factors that can hinder bathymetric data acquisition, leading to incomplete bathymetric mapping coverage [1]. Multibeam Echosounder (MBES) bathymetric surveys are typically limited to depths of more than 10 m in order to minimise the risk of survey vessels running aground and to optimise the sonar beam swath width [2,3]
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