Water Surface Topography Measurements with the RSSG
A new optical instrument for the measurement of surface wave slope and height properties was recently developed at the University of Heidelberg. The abilities of this Reflective Stereo Slope Gauge (RSSG) to measure the two-dimensional surface topography will be demonstrated. The RSSG overcomes the usual inaccuracies of stereo triangulation at specular surfaces by using properly positioned artificial light sources. The stereo images of a water surface patch with a size of about 1 m2 are filled with specular reflections that are very similar to sun glitter. An algorithm was developed that precisely determines the water surface elevation for all specular reflections and interpolates over image areas without visible reflections to yield two-dimensional surface topography. Results from both a test on a pier near Lamont-Doherty Earth Observatory and the OSSPRE 2011 experiment on the Kilo Moana in the Pacific Ocean are presented to demonstrate the wide range of environmental conditions under which measurements are possible.