B&G H2000 Pilot *DISCONTINUED* - Manual (Page 94)

h2000 User Manual
94 HB-0845-06
CAL VAL 2
Setting
Description
0
Default setting. Uses the
boat speed sensor(s)
connected to the main
processor.
1
Uses an external boat speed
source. For example, a
paddlewheel sensor
connected to a pilot
computer or NMEA boat
speed decoded by the main
processor.
3.3 MEASURED WIND SPEED AND ANGLE
3.3.1 Principles of Wind Speed/Angle Calibration
One of the greatest problems for an instrument system to
overcome, which has not yet been conquered, is wind shear
and wind gradient. These two effects are at the root of some
apparent instrument inaccuracies. The effects themselves are
relatively straightforward and are due to the simple fact that
as moving air comes into contact with the ground it slows
and changes direction.
The slowing creates the effect called wind gradient. The
change in direction creates wind shear. Both shear and the
wind gradient depend on the amount of mixing of the wind
at ground level and the wind aloft; if the wind is well mixed
both effects are minimised. The best example of this is the
sea breeze, which starts off almost completely unmixed.
Differences of direction of 40-50 degrees between the wind
at the mast head and the wind at the water are not
uncommon in an early sea-breeze, but as the day goes on
and the sea-breeze strengthens this will disappear.