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depth contour

On a nautical chart, depth contours mark all locations that have a specific depth. They are like elevation contours on a topo map. In principle we could have contours of any value, but charts have specific ones. US charts are typically 6, 12, 18 30, 60, 120 feet and so on, but the ones printed depend on the chart. International charts will be in even meters, 1, 3, 5, 10, 20, 30, 40, etc.

Two adjacent charts may not display the same contours, which can lead to a discontinuity at the chart boundaries.

The depth contours showing on an ENC are the same ones that appeared on the paper chart (RNC) it was based upon. The new rescheming ENCs project underway at NOAA standardizes the depth contours and eliminate discontinuities. This program is new and it will be some years to complete

qtVlm has a unique feature in the Chart Info display that shows all the contours used in the ENC in view, plus an underline on the safety contour in effect.

See also safety contour.

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