Acoustic Ground Discrimination Systems (AGDS) Fast mapping of sublittoral habitats without limitations due to turbidity based on the Procedural Guideline 1-3 of the “Marine Monitoring Handbook”

What can AGDS discriminate? different types of sediments (e.g. clay, sand, pebbles, rock) different types of sediments (e.g. clay, sand, pebbles, rock) biological structures (e.g. seagrass, macroalage, mussel beds) biological structures (e.g. seagrass, macroalage, mussel beds)

Why should we use an AGDS in Environmental Impact Assessments? produce a habitat map to produce a habitat map to  find a suitable site for a mariculture facility  identify rare and fragile habitats  identify already disturbed areas produce a topographic map which is a prerequisite for many models and the selection of sampling stations produce a topographic map which is a prerequisite for many models and the selection of sampling stations  quickly estimate community parameters, guidance for selecting sampling stations  get a baseline for future monitoring

What Do We Need? Two skilled and experienced persons & helmsmann Two skilled and experienced persons & helmsmann A vessel with a stable working platform and preferably a dry cabin A vessel with a stable working platform and preferably a dry cabin An echo-sounder (typically single beam) An echo-sounder (typically single beam) An AGDS signal processor (RoxAnn, QTC, etc.) An AGDS signal processor (RoxAnn, QTC, etc.) Computer System with data logging/visualizing software Computer System with data logging/visualizing software (Differential) GPS (Differential) GPS Power Supply Power Supply Equipment for Ground Truthing … Equipment for Ground Truthing …

Survey Design AGDS Coverage

AGDS Coverage - Recommendations from the “Marine Monitoring Handbook” concentrate effort on problematic areas concentrate effort on problematic areas track spacing should be related to along-track variability (real-time visualization necessary!) track spacing should be related to along-track variability (real-time visualization necessary!) track spacing wider than 500 m is problematic track spacing wider than 500 m is problematic Tracks should extend beyond the main area of interest Tracks should extend beyond the main area of interest Shoreline should be tracked as far inshore as possible (operational depth of ship and AGDS) Shoreline should be tracked as far inshore as possible (operational depth of ship and AGDS)

Ground Truthing Method Drop-down video (preferred) Drop-down video (preferred) Towed video systems Towed video systems Grabs Grabs Side scan sonar Side scan sonar SCUBA Diving, practicable only for small areas (frequent up and downs are risky!) SCUBA Diving, practicable only for small areas (frequent up and downs are risky!)

Ground Truthing Stations cover full range of acoustic ground types (E1/E2-space, Q-space) cover full range of acoustic ground types (E1/E2-space, Q-space) cover full geographic range cover full geographic range at least 5 stations per class at least 5 stations per class focus on problematic habitats focus on problematic habitats locate stations on homogenous tracks locate stations on homogenous tracks

Data Analysis Filtering and exploration: spreadsheet, database Filtering and exploration: spreadsheet, database Interpolation: e.g. Surfer TM, VerticalMapper TM Interpolation: e.g. Surfer TM, VerticalMapper TM Classification: image processing software like ERDAS Imagine TM and Irdist TM Classification: image processing software like ERDAS Imagine TM and Irdist TM Spatial analysis and map production: GIS- Software Spatial analysis and map production: GIS- Software

Quality Assurance 1. Survey Make sure that visualized data are plausible Make sure that visualized data are plausible Make sure data are consistent in cross-tracks and close parallel tracks, track over a patch of homogenous ground at the start and finish of the day Make sure data are consistent in cross-tracks and close parallel tracks, track over a patch of homogenous ground at the start and finish of the day Avoid acoustic interference with other echo-sounders Avoid acoustic interference with other echo-sounders air bubbles under the transducer cause erratic depth records air bubbles under the transducer cause erratic depth records Avoid slow vessel speed (less than 1 mph) and rapid changes in direction Avoid slow vessel speed (less than 1 mph) and rapid changes in direction Keep accurate field log: equipment details, geodetic parameters, change of settings, disturbances, sea conditions, … Keep accurate field log: equipment details, geodetic parameters, change of settings, disturbances, sea conditions, …

Quality Assurance 2. Data Consistency between habitat maps and ground samples used for classification Consistency between habitat maps and ground samples used for classification Consistency between habitat maps and independent ground samples Consistency between habitat maps and independent ground samples Relationship between survey intensity and performance Relationship between survey intensity and performance Consistency between different AGDS data sets for the same site Consistency between different AGDS data sets for the same site

Costs