Evaluating shoreline identification using optical satellite images

A technique to extract the shoreline location from optical satellite images has been developed and evaluated for the case study site of Progreso, Yucatلn, México. A novel method to extract a satellite-derived shoreline (SDS) was developed ensuring the maximum contrast between sea and land. The area under investigation is an 8 km length of shoreline that faces north into the Gulf of México. S was validated using quasi-simultaneous in situ shoreline measurements, both adjusted to equal water levels. In situ shoreline measurements recorded the instantaneous shoreward extent of the wave run-up when walking along the beach. lidation of SDS revealed that the SDS is located consistently seawards of the in situ shoreline, explained by: a) the water depth that optical satellite image requires to identify a pixel either as sea or land, and b) the shoreward extent of the wave run-up. The overall distance between SDS and in situ shoreline is 5.6 m on average with a standard deviation of 1.37 m (in the horizontal) over 8 km of shoreline. Confidence bounds considering the shoreward extent of the wave run-up, inter-tidal beach slope variation and tidal uncertainty were computed to assess the accuracy of the SDS. S has been shown to be capable of detecting shoreline changes of less than 10 m and abrupt changes due to storms. The success of our method suggests that it should be applicable to other locations, after adapting the confidence bounds to the beach conditions.