The cartographic process of thinning millions of surveyed depths to the few that fit legibly on a chart at its scale. Selections favour shoalest values, peaks and the depth pattern a mariner needs to read the seabed, while keeping the spacing tidy. Automated tools apply shoal-biased rules and a cartographer checks the result, including that no selected sounding contradicts a contour.
Sounding selection at harbour scale has to keep the 5.8 on the bank, it's the shoalest in there.
Also heard as
- sounding thinning
- selected soundings
Related terms
Shoal-biased
Favouring the shallower value whenever depths are generalised, so a chart never shows more water than exists.
Depth contour
A chart line that follows a single depth below chart datum across the seabed.
Sounding
A single measured depth at a known position, or a depth figure printed on a chart.
Nautical chart
A map of waters and coasts made for mariners, showing depths, hazards, aids to navigation and landmarks.