Chapter 4: Setting Up the GPS Plotter |
Datum Selection
You can select either WGS 84 or LOCAL datum. In LOCAL mode, you are presented with a Datum Names list. Use the trackpad up/down to scroll through the list; press ENTER to select the option and close the menu.
Note: When the datum (reference grid) is changed, the geographical position of waypoints remains constant. However, the latitude/longitude values change as a result of their having been calculated from a different datum. When adding waypoints numerically to the waypoint list, or via SeaTalk, NMEA, it is important that they are referenced to the same da- tum in which the display is to be operated.
Position Offset
You can offset the vessel position to allow for differences between the GPS and paper chart data. This may be useful if you are using a datum that is not available on the Chartplotter, or if you are referring to a paper chart drawn to unknown datum.
You can change the offset by moving the cursor to the known vessel position. This offset is applied to all incoming position data. The default offset value is zero.
When position offset is switched on, all displayed vessel position data is annotated (C) to indicate it has been corrected.
To switch the position offset on/off:
Select the POSITION OFFSET option, then press the OFFSET OFF ON soft key to toggle the option on/off. The last selected offset value is added to position data and the vessel is displayed at the corrected position.
To set a new offset value:
Select the POSITION OFFSET option, then press the SET UP OFFSET soft key. If necessary, position offset is automatically toggled on.
Use the trackpad to move the cursor to the required vessel position; the cursor position is displayed in a position offset data box.
Press the ACCEPT OFFSET soft key, the vessel is displayed at the new position. Press ENTER to return to the default display.
To set the offset value to zero:
Select the POSITION OFFSET option, then press the SET UP OFFSET soft key Press the CANCEL OFFSET soft key. The position offset value is set to zero
