Halytech
hydroSpider2 User’s Manual v1.23
Page 30
Evapotranspiration
: Uses the Hargreaves model to calculate estimated daily
evapotranspiration, based on mean daily temperature and total solar radiation.
Wind Speed and Direction
: Various methods for calculating average wind speed or
direction, or Sigma Theta (standard deviation) of wind direction are available:
o
Wind Speed Vector Avg
and
Wind Direction Vector Avg
: These methods each take
two inputs representing instantaneous wind speed and direction, and combine them
to calculate the vector average wind speed and direction.
o
Wind Direction Average
: Takes an input representing instantaneous wind direction
and calculates the average direction, correctly handling the transition between 360
and 0 degrees.
o
Wind Direction Sigma Theta
: Takes an input representing instantaneous wind
direction and uses the Yamartino method to calculate the standard deviation of the
wind direction.
The average or standard deviation is calculated over the super channel’s logging period in
each case.
Super channels are included in reports and can be used to trigger alarms, in the same ways as native
or system input channels.
They cannot however be calibrated, because it is assumed that the input channels are already
calibrated, and the super channels perform their calculations or lookups based on the calibrated
input readings.
