Gary Hayman

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This work was undertaken to devise a technique to measure the height of crops in farmland elds through remote sensing. Crop height is a useful spatial variable which, when measured by ground-based manual survey, has proven to be an important predictor of bird species population. An airborne scanning laser system capable of measuring topography to a height(More)
A technique for evaluating the underwater acoustic performance of panels under simulated ocean conditions in a laboratory test facility is described. The method uses a parametric array as a source of sound within a test vessel capable of simulating ocean depths down to 700 m and water temperatures from 2 to 35 degrees C. The reflection loss and transmission(More)
A comparison is made of two methods for determining the phase response of hydrophones in the kilohertz frequency range: The three-transducer spherical-wave reciprocity method and the method of optical interferometry. The implementation of the methods and the corresponding experimental systems are described. To facilitate a comparison, the methods are used(More)
The use of autonomous recorders is motivated by the need to monitor underwater noise, such as in response to the requirements of the European Union Marine Strategy Framework Directive. The performance of these systems is a crucial factor governing the quality of the measured data, providing traceability for future underwater noise-monitoring programs aimed(More)
The current primary method for hydrophone calibration is the three-transducer spherical-wave reciprocity at NPL, covering the frequency range between 1 kHz up to 500 kHz with expanded uncertainties as low as ± 0.5 dB. Optical methods can provide an alternative method for primary calibration as they directly measure the acoustic particle velocity at a(More)
An absolute calibration method has been developed based on the method of three-transducer spherical-wave reciprocity for the calibration of hydrophones when immersed in sandy sediment. The method enables the determination of the magnitude of the free-field voltage receive sensitivity of the hydrophone. Adoption of a co-linear configuration allows the(More)
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