The figure to the right demonstrates the repeatability of the survey methodology by showing a section of a beach profile surveyed by three different GPS operators on the same day.  The top graph shows the actual data collected by the three operators.  The bottom graph illustrates the mean vertical difference between survey operators: the difference between operator 1 and operator 2 (blue line) was 2.2 cm (0.86 in) with a standard deviation of 3.7 cm (1.45 in), and the difference between operator 1 and 3 (green line) was 0.6 cm (0.25 in) with a standard deviation of 3.8 cm (1.5 in).

The low mean offsets and standard deviations of this and other tests suggest that errors introduced by walking the profiles with a GPS backpack are small relative to the seasonal variability experienced on CRLC beaches. Click on the graphic for an enlarged view.