lying on a cross-shore profile results in an estimate of the three-dimensional 

 profile. 



Nevertheless, the primary use for the system has been runup measurements, 

 very similar to measuring a profile. Camera geometry is determined from 

 ground control points in the manner described above. A measured beach 

 profile (X,Y,Z) is transformed into corresponding video coordinates. Pixel 

 intensities are recorded along the video profile in a single video frame, each 

 pixel having an associated ground coordinate. A typical sampling rate would 

 be 6 Hz, with postprocessing decimation to 2 Hz. Pixel intensities on each 

 profile are scanned for an abrupt change in intensity, detecting the swash edge, 

 at which point the measured video coordinate is transformed to a runup 

 elevation (Equation B9). 



In principle, video measurement of runup could be automated to include 

 routine measurement of beach profiles, reducing errors associated with 

 temporal changes (i.e., difference between actual and assumed profiles). This 

 method of using video to measure subaerial beach profiles was demonstrated by 

 Holman et al. (1991) to have vertical accuracies of approximately ±}h pixel, or 

 about ±5 cm at 100 m from the camera. This technique would allow for 

 routine collection of long time series of subaerial profiles and runup to study 

 beach climatology. 



A present limitation with this system is that video runup measurements are 

 typically done in daylight hours, whereas profile measurements (done by 

 casting a light beam) would be done under low light conditions. Night-time 

 runup measurements could be done along the lighted profile at night, but the 

 lighted profile would be difficult to see in the daytime. Stereo-photography 

 would be one method of making daytime measurements of beach profiles (over 

 the swash excursion) and runup without beach surveys or "light beams. " 



B4 



Appendix B Photogrammetry 



