shows scatter plot of sample test site over rugged
mountainous areas (subfile from N40W107). (a) Voids in the
original SRTM DEMs, (b) Scatter plot of errors that fell within
±16 m were randomly distributed, (c) Scatter plot of errors that
fell within ±32 m, (d) Scatter plot of errors that fell fell outside
of ±32 m tended to group around void areas of the original
SRTM DEMs