CUBE Bathymetric data Processing and Analysis

Introduction

The Canadian Hydrographic Service (CHS) has been using Caris-HIPS as its main bathymetric processing tool. This document outlines the optimal CUBE processing workflow and methodology in order to obtain high quality Bathymetric Surfaces and their associated uncertainties.

1 Data acquisition best practice

The quality of the final bathymetric surface is directly related to the quality of the acquired data. It is therefore important for the hydrographer to understand and execute a rigorous data acquisition methodology, be able to recognize the problems as they occur and apply the adequate corrective actions before the end of the survey. This will considerably reduce the CUBE processing time and the bathymetric surface uncertainties.

2 Minimising the systematic errors

Table 1 is designed to be used for the preparation of surveys as well as the processing of bathymetric data. It should be used as a guideline for the optimization of the acquisition and processing in order to obtain the best extract of a bathymetric dataset. To achieve the resolution and precision listed in Table 1, the hydrographer must take into account the characteristics of the survey equipment and adapt the survey methodology (see notes in the Table 1). CHS has determined a depth up to which the data must be checked and validated to ensure that all shoals are included in the final surface. This depth limit is set to navigational characteristics of the area plus a safety margin or the maximum of 50 meters. In depths greater than 50 meters, CHS will ensure a minimum validation of the data.

Table 1 : Recommended Base surface resolution

Depth up to Surface resolution Size of features detected POSACC SOUACC Positioning system requirement CHS Order Comments
15m 0.25m 0.125m <0.19 RTK PPK Exclusive Special
25m 0.50m 0.25m <0.31 RTK PPK Special
50m 1.00m 0.50m <0.45 PPP DGPS WASS C-Nav Starfix Special Shoal validation limit
100m 2.00m 1.00m <1.39 Standalone post-processing 1
100m+ 5.00m+ 2.50m+ <2.51+ Standalone GPS 2

Notes:

  • CUBE surface resolution should have at least 5 pings per cell in order to achieve the resolution specified in column #2.
  • The location and the order of the survey are taken into account when determining the SVP, acquisition and tide reduction strategies to be used (i.e. distance from the tide station gauge, sound speed at the transducer head, limit the swath angle, frequencies, etc.).
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