Triton BathyPro - Manual (Page 73)

Figure 36. Fill Filter Settings dialog box
In this dialog box you have four entities you can influence here:
• Median Filter — A median filter requires that there be a minimum number
of neighboring cells containing accepted data within the selected filter
dimensions. The function then calculates a value for the empty cell based
on the median value of those cells.
• Inverse Distance Filter — An inverse distance filter calculates a value for
an empty cell based on the values of accepted data in neighboring cells
within the selected filter dimension, multiplied by the inverse of the distance
from those cells. This means that the value of the filled cell will be biased
towards the depth value in the closest cell(s).
• Number of Neighbors — When using either filter, specify the number of
neighbors, from 1 to 1001. Practical values probably lie in the range 3–9.
The larger the value, the more intensive is the processing.
• Filter Dimension in pixel units — The filter dimension allows you to vary
the strength in the north-south and east-west directions, based on the
number of pixel units. The pixel unit comes from the grid resolution in the
map setting, set in the beginning of the process.
The effect of these two types of gap filling is that a median filter generates a
less smooth DTM than an inverse distance filter does, which may smooth
out a genuinely rough bottom. The user should decide which to use based
on his knowledge of the bottom topography and his observations of the
data.
June 2004 BathyPro User’s Manual
73