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Source Diagrams

Each NOAA chart has a Source Diagram that shows the vintage of hydrographic surveys on which the chart is based. Depths on some parts of the chart may be based on pre-1900 hydrographic surveys conducted with sextants and leadlines. Full bottom coverage surveys on other areas of the chart may have been conducted with modern GPS and multibeam survey instrumentation.

The Source Diagram helps the mariner evaluated the reliability of depths found on NOAA charts.


This is a graphic of a Source Diagram that is shown on NOAA nautical charts.  It shows a small scale rendition of the nautical chart.  Different areas are outlined that show what dates that surveys were conducted in these areas.  In addition, it details the type of survey that was performed, such as partial bottom coverage, leadline, or full bottom coverage.
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