Quantifying Tidal Mud Flat Elevations From Fixed-Platform Long-Wave Infrared Imagery

A procedure for estimating tidal mud flat topography from fixed-platform, long-wave infrared imagery is presented. Shallow water and low bearing capacity on many mud flats hinder traditional surveying methods by water craft, walking, or land vehicle. The approach utilizes identification of the intersection of water with the surface of the mud flat through a rising tide. Waterlines on mud flats are often indistinguishable to the naked eye and in visible-band imagery. Long-wave infrared imagery, relying on emitted radiance, provides a more distinct delineation between an exposed mud flat and water. The waterline is identified via an image intensity threshold and transferred to real-world coordinates using a geometrical transformation model that accounts for potential imager sway. Elevation estimates, interpolated to a uniform grid, show excellent agreement (absolute error generally less than 0.02 m) with ground truth elevations obtained using a sled-mounted global positioning survey system.