Flytec Windwatch PRO User manual

Windwatch PRO
Pocket Weather Station
Operating Manual
Flytec AG Switzerland
Ebenaustrasse 18
6048 Horw
26.01.2008

2Overview
Overview.....................................................................................................................................3
Summary of Functions ..............................................................................................................4
Operating Philosophy................................................................................................................4
Change Main function:........................................................................................................................ 4
Change Sub function: ......................................................................................................................... 4
Backlight .............................................................................................................................................. 4
Set-Mode for the Main Display Screen .............................................................................................. 5
Set-Mode for Secondary Functions................................................................................................... 5
Select Measuring Units....................................................................................................................... 5
Start - Stop - Reset .............................................................................................................................. 5
Chart of Functions .....................................................................................................................6
Barometer...................................................................................................................................8
Barometer Pressure Display QNH / QFE........................................................................................... 8
Barometer Screens.............................................................................................................................. 9
Barometer display with time of day ......................................................................................9
Barometer display with temperature ....................................................................................9
Barometer display with max and min pressure ....................................................................9
Barometer Set-Mode ......................................................................................................................... 10
Setting the Barometer altitude ...........................................................................................10
Setting the time units for the pressure trend graph ............................................................10
Time and Alarm Clock..............................................................................................................11
Time and Alarm Clock Screens........................................................................................................ 11
Time and date display........................................................................................................11
Time with secondary time ..................................................................................................11
Alarm clock time, date and status ......................................................................................11
Time and Alarm Clock Settings........................................................................................................ 12
Setting time of day .............................................................................................................12
Setting the date..................................................................................................................12
Setting the time for a second time zone.............................................................................12
Setting the alarm time........................................................................................................13
Setting the alarm day(s).....................................................................................................13
Stopwatch and Timer...............................................................................................................14
Stopwatch and Timer Screens ......................................................................................................... 14
Stopwatch ..........................................................................................................................14
Timer .................................................................................................................................14
Race/Sail timer for regatta start .........................................................................................15
Timer Settings.................................................................................................................................... 15
Setting the timer.................................................................................................................15
Setting the pre-alarm .........................................................................................................15
Wind Speed/Wind Chill............................................................................................................16
Measuring Wind Speed..................................................................................................................... 16
Using the protective slider..................................................................................................16
Wind Speed Screens......................................................................................................................... 16
Wind speed display............................................................................................................16
Wind chill display ...............................................................................................................16
Wind Speed Settings......................................................................................................................... 17
Setting the wind speed averager .......................................................................................17
Normal Average value .......................................................................................................17
Peak Average value...........................................................................................................17
Setting wind chill calculation method .................................................................................17
Altimeter....................................................................................................................................18
General Information about Altimeters............................................................................................. 18
Altimetry For the Ambitious User .................................................................................................... 19
Temperature of the air column...........................................................................................19

Overview 3
Normal atmosphere Table.............................................Fehler! Textmarke nicht definiert.
Altimeter Screens...............................................................................................................................20
Absolute and relative altimeter display .............................................................................. 20
Cumulative ascent and descent display ............................................................................ 20
AutoSet display .................................................................................................................20
Altimeter Settings...............................................................................................................................21
Setting altimeter/ QNH pressure........................................................................................ 21
Setting the air column factor.............................................................................................. 21
Setting the reference altimeter (ALT 2) ............................................................................. 21
AutoSet................................................................................................................................................22
Setting the time and altitude for AutoSet ........................................................................... 22
Temperature and Humidity .....................................................................................................23
Temperature and Humidity Sensors.................................................................................................23
Dew Point .......................................................................................................................... 23
Temperature Measurement............................................................................................... 23
Temperature and Humidity Screens.................................................................................................24
Temperature and humidity display .................................................................................... 24
Temperature graph with minimum/maximum values ......................................................... 24
Humidity graph with minimum-/maximum values .............................................................. 24
Temperature and Humidity Screen Settings....................................................................................25
Setting the time units for the trend graph .......................................................................... 25
General information.................................................................................................................25
Battery.................................................................................................................................................25
Malfunction.........................................................................................................................................26
Care and Maintenance.......................................................................................................................26
Warranty...................................................................................................................................26
Water Damage ....................................................................................................................................26
Disclaimer.................................................................................................................................26
Specifications ..........................................................................................................................27
Overview
Wind
vane
Temperature
&
Humidity
sensors
Upper
Display
Middle
Display
Lower
Display
Adjust up,
Reset
Menu
Key
Sub Menu
Key
Adjust
down
Start/Stop
key
F
u
n
ct
i
o
n I
co
n
Pr
otect
iv
e
s
li
der

4Introduction
Congratulations!
on your purchase of the pocket weather station Windwatch PRO
This operation manual provides detailed information about the operating mode of the
Windwatch PRO instrument. By using your new, multi function instrument which is equipped
with four high precision sensors, you are able to measure wind, air pressure, altitude,
temperature and relative air humidity. Moreover, your pocket weather station provides the
feature of Windchill and dew point calculation, as well as very useful functions for timer, alarm
and alarm clock. The purpose of this operating manual is to make yourself familiar with the easy
handling of the instrument and to stimulate at the same time the comprehension for
meteorological correlation. Some more comments related to meteorology-physical conditions
are specifically addressed to the ambitious user.
Summary of Functions
The Windwatch PRO provides the following six main function screens, shown with
corresponding symbols that are visible in the upper part of the display:
Sub
function
Wind Gauge
Sub
function Sub function
Stop Watch
Timer
Time
Alarm Clock
Sub
function
Barometer
Altimeter Humidity
Temperature
Sub
function Sub
function
Within any main function screen it is possible to access one or two sub-screens
Operating Philosophy
Change Main function:
Ashort press of the MENU key scrolls, in a loop, from one main screen to the next main
screen (see page 6 chart of functions).
Change Sub function:
Ashort press of the SUB key scrolls through the possible sub-screens within each main
screen.
2
Backlight
Long-press the MENU key for 2 seconds to activate the display backlight. The backlight
consumes higher-than-normal battery power; therefore it is recommended that it only be used
when the display could otherwise not be read. When the battery condition is weak, the backlight
function is automatically disabled and a “No Li” message is briefly shown in the display upon the
next menu change. All other functions of the instrument remain operative until the battery is
completely exhausted.

Introduction 3
4
SEC
Set-Mode for the Main Display Screen
A long press (4 seconds) of the MENU key brings up the set-mode for the current main function
shown on the upper line of the display. With the WWP in set-mode, the value to be set will be
flashing and can be adjusted with the UP and DOWN keys.
Example: When the WWP is in the Altimeter screen, pressing the MENU key for 4 seconds
allows the altitude to be adjusted.
Use a short press of the MENU key to escape set-mode – or, if no key is pressed for 7 seconds,
set-mode is automatically escaped.
Set-Mode for Secondary Functions 4
SEC
A long press (4 seconds) of the SUB key gives access to the set-mode for that secondary
function (the values on middle and lower lines of the display). When in set-mode, the value to be
set will flash and can be adjusted with the Sand Tkeys.
Example: When the WWP is in the Altimeter screen, pressing the SUB key for 4 seconds allows
the adjustment of the Relative Altimeter.
A short press of the SUB key will accept the value that is flashing and will cause the next value
that can be adjusted (if any) to flash. If there is no further value to be adjusted, a subsequent
press of the SUB key will escape set-mode – or, if no key is pressed for 7 seconds, set-mode is
automatically escaped.
Select Measuring Units
A short press of the Sor Tkey in any display screen will change the measuring units. If there
are more than two possibilities, subsequent shot presses will scroll through the choices.
Example: In the Altimeter screen, a short press of either arrow key will change the display from
meters (m) to feet (ft).
Start - Stop - Reset
When the WWP is in the Stopwatch screen, the left key is used to start and stop the stopwatch.
A short press of the right key marks the interval time, whereas a long press resets the
stopwatch to zero.
A long press of the RES key resets the primary displayed value of the current function shown on
the display. Example: in the Altimeter screen, the reference altimeter can be reset to zero with a
long press of the RES key.

6Introduction
Chart of Functions
1
• Barograph • Time of day • Stopwatch
• Current air pressure • Date • Interval (lap) time
• Time • Year • 2nd Interval time
• Barograph • Time • Countdown timer
• Current air pressure • Remaining time
• Current Temperature • Secondary time • Pre-alarm interval
• Barograph • Alarm time • Countdown timer
• Air pressure maximum • Alarm days or date • Remaining time
• Air pressure minimum • Alarm ON / OFF • Pre-alarm interval
Timer
20:00
13:23
2:00
1:00:00
56:18
10:00
Race Timer
1013.2 hPa
22.6°C
Barometer /Temp
15:13:25
9:13:25
Time / 2nd Time
1018.6 hPa
996.4
Barometer Max/Min Alarm Clock
ON
6:00
1-7
1013.2 hPa
02:38:27
Barometer / Time
14:23.2
9:23.4
4:15.5
Stopwatch 
Time / Date/ Alarm
2008
9:13:25

12 4



Introduction 3
2
• Current wind speed • Absolute alt. (MSL) • Temperature
• Average • Relative alt. (AGL) • Relative humidity
• Peak • Rate of ascent/descent • Dew point
• Current temperature • Absolute alt. (MSL) • Temperature graph
• Wind speed • Maximum altitude • Max. temperature
• Wind chill • Minimum altitude • Min. temperature
• Current alt. (MSL) • Dew point graph
• Adjustment altitude • Max. dew point
• AutoSet time • Min. dew point
• Rel. humidity graph
• Max. rel. humidity
• Min. rel. humidity
 
Temperature
Moisture
40
24.5
Wind Speed
2.5
4.8
6.2
Altimeter
Alt. Max / Min
2649
2864
182
m
m
AutoSet
2649
1150
6:00
m
Tem
p
erature
26.2
18.3
°C
Dew Point
10.8
6.2
DP
Rel. Humidit
y
64
67
%RH
15
4.8
22
m/s
°C
°C
Wind Chill
2649 %RH
10.9
°C
DP
m/s
m
°C
86
Alti
120
m/h
(

8 Barometer
Barometer
By tracking air pressure trends at a given location it is possible to make predictions
about approaching weather conditions. The barograph on the WWP Barometer main
screen represents the air pressure progression over the past 3, 6, 12 or 24 hours (user
selectable where each bar represents 1/12th of the period selected). The graph runs from
left to right so that the value on the left is the oldest and the value on the right is the most
recent. Each segment in a bar corresponds to a pressure change of 2 hPa. The WWP
measures and updates the digital air pressure display every 7.5 minutes.
If the diagram is ascending from left to right, it signifies an increasing barometric
pressure trend, which is generally associated with dry weather conditions, sunshine and
blue skies. Conversely, if the graph is decreasing from left to right it indicates decreasing
barometric pressure, generally associated with a warm or cold front. For alpinists, hikers,
pilots and other outdoor sportsmen this is a warning sign for the possibility of bad
weather and the need to watch for worsening conditions. These front systems very often
produce a change in the weather, combined with low clouds and the possibility of
persistent rains or snow.
Barometer Pressure Display QNH / QFE
Because air pressure decreases with altitude, it is necessary to relate air pressure at a
given elevation to the air pressure at sea level. In meteorology this value is referred to as
QNH. The average pressure at sea level during one year over medium latitude is
1013.25 hPa; this was set as standard pressure by the ICAO for the flying sector in
1928.
To measure air pressure at an altitude other than sea level, you must enter the altitude
of your current position into the barometer. In the WWP this height value is entered in
the set-mode for the Barometer screen. This also means that if the instrument is moved
to a location with a different elevation, the new reference elevation must be entered. If
the altitude of the WWP changes by more than 50 meters within a short period of time,
the barometric graph is automatically cleared and restarted.
If the reference altitude is set to zero, the displayed pressure is the actual air pressure at
that elevation and is referred to as QFE (Absolute Pressure).

Barometer 9
Barometer Screens
Barometer display with time of day
This display shows the barometric pressure trend, current
pressure and time of day. The pressure can be changed to hPa
or inHg with a short press of the Sor Tkeys.
1013
hPa
0
2:
Barometer display with temperature
This display shows the barometric pressure trend, current
pressure and temperature. The pressure units hPa or inHg can
be selected with a short press of the Sor Tkeys. The units for
the temperature (°C or °F) can be set in the Temp/Humidity
screen.
Barometer display with max and min pressure
This display shows the barometric pressure trend, current
pressure and the maximum and minimum pressure value within
the graph period. This period can be set in the Barometer set-
mode. The pressure units hPa or inHg can be selected with a
short press of the Sor Tkeys.
38
:27

1013
hPa
2
3
.1 °C
1015
hPa
1
008

10 Barometer
Barometer Set-Mode
4
SEC Setting the Barometer altitude
A long press (4 seconds) of the MENU key gives access to the
Barometer set-mode and will cause the barometer reference
altitude to blink. Use the Sand Tkeys to set the altitude for
your current location. This setting is necessary to obtain a
precise QNH indication (see barometer general information
above).
1013hPa
456 m
4
SEC
Setting the time units for the pressure trend graph
A long press of the SUB key allows the time period represented
by each bar on the pressure trend graph to be set. Use the S
or Tkeys to scroll through the values of 15 minutes, 30
minutes, 1 hour or 2 hours per bar. The WWP maintains the
barometric pressure values for the past 24 hours regardless of
the time period set for the graph. This means that you can
reduce the time period at any time to show greater detail, or
increase it to show the longer term trend.
1h00
Note: When you select a screen containing a trend graph, the
display will show the graph interval for 2 seconds before the
graph appears, to remind you of the time period per bar of the
graph (1 hour 0 minutes per bar in the example above).

Time and Alarm Clock 11
Time and Alarm Clock
Time and Alarm Clock Screens
This menu provides the time in 24h or 12h format, with an alarm clock as well as the time in a
secondary time zone. The alarm clock can be set to a predetermined time of day, and to reoccur
daily, week-days only, week-ends only, or on a specific date.
Time and date display
2
005
9:13:25
am
11 - 14
This screen shows the time and date. A short press of
the Sor Tkey will toggle the time between 24h or 12h
(am/pm) format. In 12h format the date is shown as mm-
dd-yyyy. In 24h format the date is shown in as dd-mm-
yyyy.
Time with secondary time
This screen shows the time and a secondary time.
Normally the time shown in the upper line of the display
would be set to the local time, and the secondary time,
shown in the lower line, would be set to show the time in
another time zone. Both times can be displayed in either
24h or 12h format with a short press of the Sor Tkey.
2:1
3
:2
5
pm
9:13:25
am
Alarm clock time, date and status
This screen shows the alarm clock time on the top line,
the alarm date on the second line (or recurring days as
programmed in the Alarm set-mode), and the status of
the alarm clock (On or Off) on the third line. The alarm
clock is enabled or disabled with a long press
of the Sor Tkey.
O
n
7:05
01-01-05
am

12 Time and Alarm Clock
Time and Alarm Clock Settings
Setting time of day
4
SEC A long press of the MENU key allows the current time to be set.
First the hour field will flash; adjust with the Sand Tkeys,
then short-press the MENU or SUB key to accept the hour
setting and advance to the minutes field. Set the minutes with
the Sand Tkeys, then short-press the MENU or SUB key to
accept the minutes setting and advance to the seconds field.
Short-press the Sor Tkey to set seconds to zero. Short-press
the MENU key to return to the main screen – or, if no key is
pressed for 7-seconds, the WWP will automatically return to the
run mode.
9:13:25
am
9:13:25
am
4
SEC Setting the date
A long press (4 seconds) of the SUB key allows the current
date to be entered. The blinking values can be adjusted with
the Sand Tkeys, and a short press of the SUB key accepts
the setting and advances to the next field to be set. In 12h
mode the date format is mm-dd-yyyy and in 24h mode the
format is dd-mm-yyyy.
Setting the time for a second time zone
The WWP must be in the Secondary Time screen (with the
globe symbol in the lower left corner of the display). Press the
SUB key for 4 seconds, then set the hour offset between local
time and the secondary time zone using the Sand Tkeys.
The hour offset is positive for time zones east of your local time
zone and negative for time zones west of you local time zone.
Japan, for instance, is ahead of the Central European time by
eight hours (+8:00).
4
SEC
-
5
:
00
2
005
1 - 1

Time and Alarm Clock 13
4
SEC
Setting the alarm time
The WWP must be in the Alarm sub-screen (alarm clock
symbol in lower left corner of display). Press the MENU key for
4 seconds; the hour field will blink and can be set with the S
and Tkeys. Short-press the MENU key to accept the hour
setting and advance to the minutes field, then set the minutes
and press MENU to accept the minutes and return to the run
mode.
07:05
Setting the alarm day(s)
4
SEC
The WWP must be in the Alarm sub-screen (alarm clock
symbol in lower left corner of display). Press the SUB key for 4
seconds to access the alarm day set-mode. The current setting
will blink and can be changed with Sand Tkeys. The
following five alarm types are:
01-01-05
1-7 alarm clock rings every day
6-7 alarm clock rings Saturday and Sunday only
1-5 alarm clock rings Monday through Friday only
-dd- alarm clock rings only on a pre-determined date
123_ alarm clock can be set to any day of the week
To set the WWP to ring on a recurring day of the week, select
“123_” as described above, short-press the SUB key and select
the desired day with the ▼or ▲keys (1=Monday and
7=Sunday).
To set the WWP to ring on a specific day, select “-dd-”as
described above, short-press the SUB key, and enter the date.
The year will blink first and can be set with the▼and ▲keys,
short-press the SUB key to accept and advance to the month,
set the month and short-press the SUB key to accept and
advance to the day field. Set the desired day and short-press
the SUB key to return to the run mode.
Note: The alarm clock function is toggled ON/OFF with a long press of the ▼or ▲key (WWP
must be in the Alarm sub-screen).

14 Stop Watch and Timer
Stopwatch and Timer
Stopwatch and Timer Screens
The WWP features a full-function stopwatch with 1/10th second accuracy, a countdown timer
and a sailing/race timer. Both timers feature a pre-alarm warning that can be user set. The pre-
alarm for the racing timer was designed for regatta starts in sailing. If a pre-alarm is set, the
WWP will beep for 3 seconds at the pre-set interval before the end of the timer period.
Stopwatch
On this screen the top line shows the running time in minutes,
seconds and tenths of a second. The middle line shows the
new interval (lap) time and the bottom line presents the
previous interval time.
15:28.2
13:23.4
8
:1
5
.
5
Short-press to start and stop stopwatch
Short-press to record interval (lap) time while the
stopwatch is running
A long press resets the stopwatch back to 0.0.
The lap times are maintained.
A long press resets the stopwatch and interval
times to 0.0.
Timer
15:00
13:25
3
:
00
The top line shows the user-set timer period, the second line
shows the remaining countdown time, and the bottom line
shows the period of time that the pre-alarm will sound in
advance of the timer alarm (countdown time=0). The timer is
started and stopped with the Xkey.
A long press of the RES key sets the countdown time (middle
line) back to the timer setting as shown on the top line of the
screen. When the countdown timer reaches the pre-alarm
value, the WWP will beep for 3 seconds. When the countdown
time reaches 0, a final alarm sounds and will continue until
any key is pressed

Stop Watch and Timer 15
1:00:00
56:18
1
0
:
00
Race/Sail timer for regatta start
The race timer is differentiated from the normal countdown
timer by a sailboat icon in the top of the display. When the race
timer is selected, the WWP will beep once per second during
the last 5 seconds of the countdown period, followed by a
longer beep when the countdown reaches 0. The pre-alarm still
functions for the race timer in the same way as for the standard
timer.
Timer Settings
The settings for the standard timer and the race timer are the same.
Setting the timer
4
SEC With either the bell or sailboat icon showing in the top of the
display, press the MENU key for 4 seconds to set the timer
period. The hour field will blink first and can be set with the▼
and ▲keys; short-press the MENU key to accept and advance
to the minutes field, then set the minutes and short-press the
MENU key to accept and advance to the seconds field. Set the
desired value and short-press the MENU key to return to the
run mode. The maximum timer setting is 99 hours, 59 minutes
and 59 seconds. The timer is started with a short press of the X
key, which is also the stop key.
0:15:00
4
SEC Setting the pre-alarm
The WWP must be in the Timer screen (bell or sailboat icon in
the top of display). Press the SUB key for 4 seconds, then set
the pre-alarm period in the same way as the timer period
(above). The maximum time for the pre-alarm is 99 hours, 59
minutes and 59 seconds and the minimum time is 10 seconds.
A setting of 0:00 deactivates the pre-alarm.
3:00

16 Wind Speed
Wind Speed/Wind Chill
Measuring Wind Speed
The Windwatch PRO is designed to precisely measure the wind
speed regardless of the prevailing air density. In order to obtain
optimal results, the instrument should be held vertically into the
wind with an outstretched arm. To insure the greatest accuracy,
measurements should be taken where there are minimal
obstructions upwind of your position that might cause turbulence.
Using the protective slider
MENU
SUB RES
MENU
SUB RES
The internal impeller in the WWP is precisely balanced and suspended
on two sapphire bearings and is sensitive to dust, dirt and impact. To
protect the impeller and the temperature and humidity sensors, the
WWP is equipped with a convenient protective slider that should be
closed whenever measurements are not being taken. Using the
protective slider will insure many years of reliable service from the
internal sensors.
Wind Speed Screens
15.4
18.2
22.
8
m/s
Wind speed display
The top line shows the current measured wind speed, the
middle line shows the average wind speed, and the bottom line
shows the peak wind speed value during the measuring period.
The speed can be displayed in the units m/s, km/h, knt, beauf,
ft/s and mph. Scroll through the measuring units with the▼or
▲key.
Wind chill display
Wind chill is the perceived temperature when the wind speed is
applied to the ambient temperature. The top line shows the
wind chill temperature value, the middle line shows the average
wind speed, and the bottom line shows the ambient
temperature without the wind chill factor. The measuring units
for the wind speed can be scrolled with the▼or ▲key.
-
5
.
3
-10.8
m/s
°C
°C
15.4

Wind Speed 17
Wind Speed Settings
Setting the wind speed averager
4
SEC With the WWP in the Wind Speed screen (propeller icon shown
in the top of the display) press the SUB key for 4 seconds to
bring up the wind speed averaging period. Set the period
between 5 and 30 seconds (in 1-second increments) using the
▼and ▲keys. Press the SUB key to accept the setting and
advance to select the averaging method for the average wind
speed display. The options are normal average and peak
average, and are selected with the ▼or ▲key.
10 SEC
Normal Average value
This method displays a running average of the wind speed over
the selected period. Each second, the oldest wind speed value
is deleted and the average is recalculated with the most recent
wind speed reading.
Peak Average value
This method displays and maintains the maximum average
wind speed value with no time limit. The peak average value
display is reset by pressing the RES key for 4 seconds.
Setting wind chill calculation method
With the WWP in the Wind Chill screen (propeller icon shown in the top of the display and the
snowflake icon shown in the left of the display) press the SUB key for 4 seconds and select the
wind chill calculation method. In 2000 the formula for calculating wind chill was changed; use
the ▼or ▲key and select the OLD or NEW formula. The graph below shows the difference
between the two calculation methods. More detailed information on the two calculation methods
can be found on meteorological websites.
4
SEC
NEW

18 Altimeter
Altimeter
The Windwatch PRO has a state-of-the-art pressure sensor that, in addition to providing precise
barometric pressure readings, provides a fully developed and highly accurate altimeter. The
altimeter is fully temperature compensated so that the displayed altitude does not change when
the temperature of the WWP changes.
General Information about Altimeters
Barometric altimeters calculate altitude based on air pressure. Air pressure decreases as
altitude increases. Due to the fact that air is compressible, the pressure decrease is not linear,
but exponential. The calculation for deriving altitude from air pressure is based on an
international formula (Commision International de Navigation Aérienne) and assumes a
standard atmosphere with idealized characteristics. The CINA standard atmosphere assumes
that the pressure at sea level is 1013.25 hPa (Hektopascal) at 15°C. A continuous decrease in
temperature at the rate of 0.65 °C per 100 meters of ascent is also assumed. Consequently, a
barometric aviation altimeter only displays the correct altitude if weather conditions are
consistent with the standard atmosphere.
In practice, these conditions are more likely to be an exception! The WWP incorporates a Flytec
innovation that significantly improves the altitude accuracy by correcting for air column
temperatures. If this feature is used, the correction is applied to the CINA altitude formula,
making the altitude readings on the WWP more accurate than standard altimeters. The
correction need not be used, in which case the altitude readings will coincide with aircraft
altimeters.
Atmospheric pressure also changes due to prevailing weather conditions. Depending on the
weather, the air pressure at sea level (QNH) may vary from 950 to 1050 millibars (mb). Even on
a stable day, temperature-induced differences in air pressure of ±1 mb may occur, equivalent to
a height difference of ±8 meters. During rapid weather changes, such as the passage of a cold
front, the air pressure may change up to 5 mb within one day, corresponding to an altitude
change up to 40 meters. Consequently, an altimeter must be calibrated prior to each use. This
means the altimeter must be set to a known benchmark altitude (e.g., airport, launch site, topo
map, elevation marker, etc.). An alternate method for setting an altimeter is to enter the current
QNH pressure reported by local aeronautical weather reports or reliable meteorological
institutions.
The Windwatch PRO features another Flytec innovation (patented), called AutoSet. When this
feature is enabled, the instrument automatically factors out changes in the altitude reading that
were caused by changes in the weather. For more information on this feature see the AutoSet
heading later in this section.

Altimeter 19
Altimetry For the Ambitious User
Temperature of the air column
The standard altimetry formula was developed for aircraft in 1928. It is based upon an average
temperature of 59ºF (15°C) at sea level and an average temperature drop of 0.65°C per 100
meters. In the case where the actual air column is warmer, the air will be packed less densely. If
you are standing on top of a mountain, there will be more air particles above you than normal
and the air pressure will be somewhat higher. Therefore the altitude calculated according to the
standard formula will be too low. In the case where the actual air column is colder, the cold air
will be more dense and concentrated at ground level with fewer air particles above. Therefore
on top of a mountain the air pressure will be slightly lower at your position and the altitude
displayed will be higher than actual. On top of a 14,000 ft peak this situation can result in a 500
ft error!
Example: A temperature gradient deviation of 1°C per 1000 meters induces approximately a 4-
meter error (this empirical formula is valid for up to 4000m). At an altitude of 2000m during
summer where the air mass is 16°C warmer compared to the standard atmosphere, a standard
altimeter will display 2 x 4 x 16 = 128m lower than actual.
Note about correcting air column temperature: While the Windwatch PRO makes it possible
to increase altimeter accuracy by compensating for air column temperatures that deviate from
standard, total compensation is not always possible due to the layered structure of the
atmosphere. When setting a correction, the WWP proposes a +8ºC setting for warmer than
standard and -8ºC setting for colder than standard. This is based on the typical temperature
deviation for the summer and winter months in geographical mid-latitudes. If you suspect that an
air column correction other than the proposed ± 8ºC should be used, ambient temperature
measurements should be taken outside in the shade and compared to the table below. Note
also that the measured air temperature may be warmer than the overall air mass due to
localized thermal activity, and that should be factored out. If the air column temperature
correction is properly applied, a significant increase in accuracy can be achieved.
Table normal atmosphere
Alt. Meter Temperature ºC Pressure hPa
0 15.0 1013.2
1000 8.5 898.7
2000 2.0 794.9
3000 -4.5 701.1
4000 -11.0 616.4

20 Altimeter
Altimeter Screens
Absolute and relative altimeter display
The top line shows the current altitude (elevation). The middle
line shows the altitude difference since the last reset of ALT2.
This relative altimeter can quickly be zeroed with a long press
of the RES key so that a vertical ascent/descent can be easily
measured. The bottom line shows the rate of ascent/descent
per hour. The units for this screen can be toggled between m
and m/h or ft and ft/h with a short press of the ▼or ▲key.
1625
70
21
8
m/h
m
ALT2
Cumulative ascent and descent display
2314
13965
-17
8
2
5
m
m
The top line shows the current altitude (elevation). The middle
line shows the accumulated ascent and the bottom line shows
the accumulated descent since the last reset. Reset of the
ascent and descent totals is performed by a long press of the
RES key. Units (ft or m) can be toggled with a short press of the
▼or ▲key.
AutoSet display
The top line shows the current altitude (elevation). The middle
line indicates the altitude that will be set by the AutoSet
function (if enabled). The bottom line shows the time when
AutoSet will set the altitude shown on the middle line (if
enabled). See the detailed instructions in section on AutoSet
below. AutoSet is toggled on/off with a long press of the ▼or
▲key.