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Navigation security
The information dialog of the chart (refer to paragraph Information on charts of the chapter Chart choice) displays important information for navigation, such as:
Depth units
Type of projection ( most of the timeÊ: mercator )
Screen Geodetic Datum (most of the timeÊ: WGS84 )
Chart Geodetic Datum (most of the time : NAD83)
Note that, according to BSB Electronic Charts, NAD83 and WGS84 are assumed to
be the same for use with NOAA navigation charts.
Latitude and longitude shifts from chart geodetic datum to WGS84 geodetic datum
In the bottom of the chart window, a small icon reminds you the geodetic datum
of the currently displayed chart. It is either WGS84, local or unknown.
All those reference informations may change from chart to chart. Be careful to
check those informations (and the consistancy with your equipments: GPS, depth
exho-sounder ·) for a safe use of the charts.