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15. NAVIGATION TOOLS
15-5
15.4 Ring
The range rings are the concentric set of rings on the chart display. They provide an
estimation of the range to an object. You can turn them on or off from the [Ring] page.
The interval between rings changes with the chart scale as shown in the table below.
15.5 Predictor
The predictor is a tool for estimating your ship's future positions and behavior. The on-
screen predictor graphic consists of three pieces of your ship, drawn in true scale to
successive future positions. The position of the third symbol will be your approximate
position at the end of the time interval selected. The predictor is calculated using cur-
rent speed and rate of turn. Docking speed components (transversal bow speed,
transversal stern speed, transversal center speed and rate of turn) are assumed to be
stable during the prediction period. The predictor can be used in every steering-state,
including manual steering.
To activate and set the Predictor, show the [Predictor] page. Turn the display on or off
with [Display]. Set the time (30, 60, 90, 120, 150, 180 seconds), with [Time].
Chart scale Ring interval (nm) Chart scale Ring interval (nm)
1:1,000 0.025 1:100,000 2.0
1:2,000 0.05 1:200,000 4.0
1:5,000 0.10 1:500,000 8.0
1:10,000 0.25 1:1,000,000 16.0
1:20,000 0.5 1:2,000,000 20.0
1:50,000 1.0
Range
ring
Movement of
predictor
(three pieces)