Evaluation of Vertical Motion Sensors for Potential Application to Heave Correction in Corps Hydrographic Surveys

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Evaluation of Vertical Motion Sensors for Potential Application to Heave Correction in Corps Hydrographic Surveys

G. C. Downing / T. L. Fagerburg

This report describes techniques and equipment that can help surveyors obtain the best practical vertical reference for hydrographic surveys in the face of adverse tide, river stage, and wave conditions. USAWES efforts involved evaluating a heave compensation system (HIPPY 120) and exploring the possibility of using Doppler equipment for measuring vertical boat motion. Some specific measurement techniques for monitoring vertical references for hydrographic surveys under given field conditions are addressed. Depth transducer draft, boat flotation plane, shore references and dynamic vertical motions of the boat hull are discussed. Vertical displacement measurement equipment using automatic electrooptical tracking systems, video-type optical tracking systems, laser leveling systems, and satellites is assessed and found to have potential for future consideration and application in improving survey accuracy. Evaluation of a heave compensation unit based on a pendulum-stabilized accelerometer platform (HIPPY 120) was attempted on a survey boat. Protracted difficulties with the system prevented a quantitative evaluation. These results lead to the conclusion that for this system to be successfully used during actual survey operations, there must be a higher-than-average level of technical skill among the personnel on the survey boat.