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Nav Tide
Nav-Tide is an absolute movement of watermass at a particular
depth, taking speed information from the external navigator
(GPS) as a pseudo ground tracking speed.
To calculate Nav-tide, the following two data are required:
1
Ship’s speed and course obtained by external navigation
equipment (GPS)
2
Ship’s speed and course based on measuring layer (A)
Nav-tide is, then, given as a difference of these two speed
vectors.
Absolute Tide =
1
–
2
GPS satellites
Nav-aided speed
(Pseudo ground tracking speed)
Water tracking
speed
Layer (A)
:Base of measurement
1
2
Figure 4
Tide Differential
Tide differential is a relative movement of tides at different
depths, layer (A) and layer (B).
To calculate tide differential, the following two data are used:
1
Ship’s speed and course based on layer (A)
2
Ship’s speed and course based on layer (B)
Tide differential between two layers is, then, given as a
difference of these two speed vectors.