ALB Technical Development — Object Detection

Abstract

According to the text taken from MO Standards for Hydrographic Surveys published by the International Hydrographic Bureau: 1 hydrographic surveys are intended for harbours, harbour approach channels, recommended tracks, inland navigation channels, and coastal areas of high commercial traffic density where underkeel clearance is less critical and geophysical properties of the seafloor are less hazardous to vessels (e.g soft silt or sand bottom). Order 2 surveys should be limited to areas with less than 100 m water depth. Although the requirement for seafloor search is less stringent than for Special Order, full bottom search is required in selected areas where the bottom characteristics and the risk of obstructions are potentially hazardous to vessels. For these areas searched, it must be ensured that cubic features greater than 2 m up to 40 m water depth or greater than 10% of the depth in areas deeper than 40 m can be discerned by the sounding The requirement above, taken from the IHO Order 1 specification, effectively defines a minimum ability for Hydrographic systems to detect a 2m cube object to complete Order 1 Hydrographic surveys. The rationale being that objects greater than that size on the seabed may pose a danger to navigation of vessels. The object detection requirement of IHO Order 1 is applied only to areas that are considered high risk for potential dangers to navigation. This distinction effectively creates two classes of IHO order 1 survey - depth and position IHO Order 1 and depth, position and object detection IHO Order 1. ALB systems are generally used to survey shallow, remote, coastal regions that are either dangerous or inefficient to survey with surface vessels utilising acoustic depth sounding equipment. The typical standard that is applied to these surveys is the IHO order 1 specification - in some cases with object detection and in some cases not. The focus of this paper is the ability of ALB systems to meet the object detection requirement when specified.