Kestrel 4300 (Construction) - Manual (Page 7)

Kestrel ® 4300 Construction Weather Tracker 13
Starting with the known barometric pressure for your location
You can obtain your current barometric pressure by checking an internet weather site
for a nearby location, or contacting a local airport. Set this value as your reference
pressure on the ALTITUDE screen to determine your correct altitude: Press the button
to enter the reference setting mode. Press the button to increase the reference
pressure or the button to decrease the reference pressure. You will notice that the
altitude will change with changes in the reference pressure. Press the button to exit the adjustment
mode. Set your Kestrel Meter down on a table and allow the altitude reading to stabilize. (Note: very small
changes in pressure generate noticeable changes in altitude. In order to provide meaningful readings for
activities where altitude changes quickly, the Kestrel Meter features rapid altitude response. This is why
the altitude readings tend to fluctuate by a few feet.) After obtaining a current altitude from the ALTITUDE
screen, move to the BARO screen and enter this value as your reference altitude by following the same
procedure. Both readings will now be accurate.
Starting with a known altitude for your location
You can obtain your altitude from a topographical map or local landmark. Google Earth
is an excellent free program that provides the exact altitude for any given address:
www.earth.google.com/. Set this value as your reference altitude on the BARO screen
to determine your barometric pressure: Press the button to enter the reference setting
mode. Press the button to increase the reference altitude or the button to decrease the reference
altitude. You will notice that the barometric pressure will change with changes in the reference altitude.
Press the button to exit the adjustment mode. Again, allow the Kestrel Meter to stabilize, then enter
the value from the BARO screen as your reference pressure on the ALTITUDE screen by following the same
procedure. Both readings are now accurate.
When reviewing stored data, remember that changes in pressure AND changes in location/altitude will
affect the stored values. When tracking pressure changes relative to weather, set the reference altitude on
the BARO screen and keep the Kestrel Meter in one location. Your graph history will now show trends in
barometric pressure. Your altitude as shown on the ALTITUDE screen will change as the weather changes,
but you can ignore this screen for this purpose.
If you are planning a day hike would like to track your altitude, you’ll need to enter the correct reference
pressure on the ALTITUDE screen as described above in “starting with the known barometric pressure.”
You can now track the altitude changes as you hike. In this instance, you should ignore the values on the
BARO screen, since the pressure changes will be due to changes in elevation far more than to changes in
the weather.
In general, changes in barometric pressure associated with weather changes are small over the course of
one day, but they will affect the accuracy of the altimeter over time. This is why aircraft reset their altimeters
at every airfield by entering the field’s “altimeter setting” or reference pressure. Accordingly, if accurate
altitude readings are your primary interest, you should reset the reference pressure on your Kestrel Meter
regularly. If you encounter an elevation landmark, you can adjust the reference pressure until the altitude
matches the landmark elevation. This will correct the altitude for any pressure changes due to the weather.
(Or, you can obtain an updated reference pressure from the sources described above.)
Some final notes - If you wish to know the actual or station pressure for your location (such as for engine
tuning), simply set the reference altitude on the BARO screen to “0”. In this case, the Kestrel Meter will not
make any adjustment and will display the measured value.
Also, the above discussion applies to ALL pressure altimeters, including one you may have in a watch or
other device, but not to GPS altimeters, which use satellite triangulation to determine altitude. Note that