Weather Conditions:
You will need low flying, puffy
clouds, with somewhat flat bottoms. A breezy day is best,
so that the clouds aren't moving too slowly.
Choosing a Site:
Set the project up in an open,
flat area. You will need to set your observation stations
up at least 60 meters (180 feet) apart while remaining
within sight and hearing of each other.
Both stations need to have an
unobstructed view of the sky in the direction that the
clouds are coming from.
Preparing the Site:
Set station #1 up at the opposite
end of the observing field from the direction the clouds
are coming from. Station #1 will have a vertical viewer
and a quadrant angle viewer.
Set station #2 up on a line
between station #1 and the direction the clouds are
coming from, at least 60 meters (180 feet) from station
#1. Station #2 will have a vertical viewer only.
Measure the distance between
stations carefully and write it down. (Make it an easy to
work with number.) Mark the two spots and place a
vertical viewer on each when you are ready to start the
observations.
The quadrant viewer will be
situated on a line between the vertical viewers, about 6
feet from station #1.
Collecting the Data:
With one person stationed at each
of the vertical viewers and the quadrant viewer, wait for
a cloud's leading bottom edge to come into view through
the vertical viewer at station #2. If possible have
another person ready to be the time keeper and data
recorder.
START the timer and signal the
quadrant viewer to record the angle read when sighting
the leading bottom edge of the cloud.
When the clouds leading edge
appears in the vertical viewer at station #1 STOP the
timer. Record start and stop times and the angle read.
Do this with several clouds to get an
average.
Processing the Data:
Look
up the Tangent Ratio for the
angle measured and MULTIPLY this by the distance between
stations. The result will be the clouds' heights above
the ground, or the altitude, in the same units as that
used for the distance between stations.
For the clouds' speed (and wind speed) in Kilometers per
Hour (KPH), DIVIDE 1000 by the number of meters between
stations; or for Miles Per Hour (MPH), divide 5280 by the
number of feet between stations. MULTIPLY the time
recorded above by this result and you have the speed (in
whatever units you took the original time reading in). If
you made the observation in minutes, MULTIPLY by 60 to
get MPH or KPH.
Repeat
for each cloud you took readings on and determine an
average altitude and speed.
