Nearshore surveying: accuracy and techniques for improvement

Various concerns of beach and nearshore survey accuracy including methodologies and equipment are addressed. First, four types of horizontal distance measurement apparatus (survey tape, infrared apparatus, microwave and optical range finder) are evaluated through intercomparison of field measurements. Second, analysis methods are developed and applied to horizontal positioning data obtained from triangulation surveys. The method provides the most probable location accompanied with a measure of uncertainty based on general characteristics of arc intersections. Finally, methods are developed for the postprocessing of standard bathymetric data obtained from a combination of land and boat surveys with a certain overlap region. The general method considers adjustments to both the vertical and horizontal positions obtained by a Fathometer and a microwave system, respectively, through offsets and linear scale factors such that for each profile line, there is a maximum of four free parameters to be optimized. The method is applied to a set of field data and compares the improvements obtained by allowing different numbers of free parameters.