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Despite recent advances in the field of seafloor geodesy, our ability to collect data to monitor for marine hazards or increase our understanding of offshore geologic processes remains limited by the exorbitant cost of data collection. We propose using the correlation of raw sidescan data, output by standard multibeam sonars, as a tool for measuring horizontal seafloor displacements. Since multibeam sonars are standard equipment for research vessels, sidescan data is routinely collected during ship transits regardless of other experiments being performed. This gives sidescan surveys the desirable quality of being relatively cheap and easy to implement in conjunction with seafaring experiments of a variety of other disciplines. In addition, sidescan data have a high range resolution independent of the platform height, and are collected from both the port and starboard sides of the ship. Averaging across these data helps to mitigate errors introduced by long wavelength sound speed perturbations in the upper water column. We analyze raw sidescan data in a range and azimuth coordinate frame by performing normalized cross-correlation on repeated surveys, finding decimeter to meter accuracy routinely achievable in the range direction. However, care must be taken when designing such field surveys, as their geodetic efficacy is highly dependent upon the tracks being closely spaced and maintaining a steady heading. We recommend the use of beamsteering when collecting such data to ensure a high correlation value.