LSI LASTEM E-Log, User Manual

Page: 33 / 62

LSI LASTEM E-Log – User’s manual
33
It’s possible to
relax some parameters in this configuration (for example the measures total number
or the active actuation logics number) in order to obtain best performances in other cases (for
example the measures activation slot)
5.3.1. Vectorial calculations specific for anemometric
quantities
Average direction (prevailing)
Dm =
   
)) ( ( )), ( ( atan2 Dir rad Cos Dir rad Sin gra
 
Resulting average direction
Dmr =
       
Vel Dir rad Cos Vel Dir rad Sin gra
   
)) ( ( , )) ( ( atan2
Resulting average speed
Vmr =
   
n
Vel Dir rad Cos Vel Dir rad Sin
2 2
)) ( ( )) ( (
    
Direction’s standard deviation (sigma theta)
DevStandDir=
   
















  

2
2 2
)) ( ( )) ( (
1 asin gra
n
Dir rad Cos Dir rad Sin
Calm Percentage
Calm = 100 *
1
n
Calm
n

Where:
Dir = instantaneous value of wind direction (0 - 360 °)
Vel = instantaneous value of wind velocity (m/s)
gra = conversion of an angle from radians to degrees
rad = conversion of an angle from degrees to radians
Calm = 0 in case of not calm wind velocity (< 0.3 m/s), otherwise 1
n = number of considered valid original data (no error)