Gill Instruments Ltd
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MaxiMet
Page 132
Issue 3
Doc. No. 1957-PS-021
May 2018
CDIR -
Correcte d D irection
Corrected Wind Direction shall be computed as the Apparent Wind Direction (i.e.: using Compass Heading)
when Compass Heading is available but any one (or more) of GPS Speed and GPS Heading are unavailable.
Corrected Wind Direction shall be computed as the True Wind Direction (i.e.: using GPS Speed, GPS
Heading and Compass Heading) when all three of GPS Speed, GPS Heading and Compass Heading are
available.
Result e.g. 116 (degrees).
Corrected Wind Direction shall not be computed when Compass Heading is unavailable.
The Gill Algorithm for generating Corrected Direction based on Compass heading is as follows:-
1. Convert Magnitude and Direction to UV.
2.
Calculate applied wind in UV due to movement from GPS.
3.
Calculate Corrected UV as difference between Relative and GPS wind.
4.
Convert UV back to Magnitude and Direction.
GDIR (WMO) -
Gust D irection
Outputs WMO Gust Direction.
Maximum Gust Direction shall be computed over a block of m vector averages as follows:
_
_
_
= arctan(
_
_
)
Where:
=
_
_
_
_
_
=
-
_
=
-
Result e.g. 123 (degrees).
CGDIR -
Correcte d G ust Direction
GPS corrected Gust Direction.
Result e.g. 135 (degrees).
