The guiding principle of charting and much survey processing: whenever data are thinned, rounded or generalised, the result must err toward shallow water. Charted depths are truncated rather than rounded, contours go around shoals, charting grids carry the shoalest sounding and selections prefer peaks. The cost is a little usable depth; the gain is confidence that no hazard is hidden.
Build the chart surface shoal-biased, the client can have the mean surface for dredge volumes.
Also heard as
- shoal bias
Related terms
Sounding selection
Choosing which surveyed depths appear on a chart so the shoalest water is always shown.
Depth contour
A chart line that follows a single depth below chart datum across the seabed.
Least depth
The shallowest depth over a wreck, rock or other feature, which is the value that gets charted.
Gridding
Turning millions of scattered soundings into a regular grid of depth values at a chosen cell size.