            USING APRS IN WEATHER AND SKYWARN APPLICATIONS


NEW in version 5.00:  Remote stand-alone operation of ULTIMETER-II
NEW in VERSION 4.05:  Wind KPH/MPH fixed and Rain made consistent to 10ths
NEW IN VERSION 3.10:  See section on National Weather Service Displays!

     The Automatic Packet Reporting System (APRS) is an ideal tool for
reporting weather conditions via packet.  The system is compatible with both
human entry as well as automatic weather station entry of weather conditions.
There is a $9 serial interface option in APRS to accept the serial output of
the ULTIMETER-II home weather station.  With this connection, your wind
conditions, temperature and optionally rain information are all automatically
inserted into your position/weather report packet.  New in version 5.00 is
the ability to parse a raw Ultimeter-II data output off the air for display
of remote weather conditions from a digipeater site with an attached U-II.
See the section below on REMOTE ULTIMETER-II OPERATION.

In the APRS system, current conditions at any station are broadcast
to all stations on the net in a periodic fashion.  Not only are these
individual conditions available to all stations on the net, but also
importantly, the location of these conditions are also displayed.  There are
several capabilities of APRS that are directly applicable to the SKYWARN:

 MAP DISPLAY - Shows the location of all reporting stations, their wind
     speed and direction.  Can also show the location of other objects, such
     as reports of TStorms, Hail, Tornados, etc

 WEATHER ONLY - Using the normal J command, Just weather stations can be
     displayed on the map to eliminate the clutter of other packet stations.
     There is a WEATHER menu of commands, and the APRS N key will cycle through
     each APRS weather station in turn and display the weather conditions for
     each one in a box on top of the screen.  The location of the displayed
     station is highlighted with a blue circle.  Whenever a new report comes
     in from the selected station, the weather window is automatically updated.

 REPORT BROADCASTS - The individual station weather conditions can be manually
     placed in the Beacon Broadcast from each station or automatically using
     the APRS WX option ($9) and ULTIMETER-II serial interface.  These reports
     are typically broadcast evrey 10 minutes.  The report is also available
     at anytime if an APRS user sends the WX station an APRS Query.  There is
     a special WX query that will request all WX stations to immediately
     report.

 STORM/HURRICANE TRACKING - Any station may place a storm or other object on
     his map, and the same symbol will be transmitted to all other stations
     in the net.  This is ideal for transmitting the location of a storm or
     Hurricane.  If the course and speed of advance of the storm is included
     in the position report, then the object will automatically be dead-
     reckoned on all screens until the next update.  Any station can update
     the location of the storm as information becomes available.  The updating
     station will automatically overwrite all posits in the net and will
     become the new reporting station for the object.  This prevents duplicate
     reporting and eliminates dependency on reporting stations that might
     disappear and not update an object that they originated.

 NOTE:  Since APRS dead-reckons the position of moving objects as time
     progresses, the symbol on the map is presented where it SHOULD be, but
     NOT where it was when first reported.  If you use the cursor to try to
     hook one of these objects on the map, you must hook the little gray
     circle which marks the position of the actual report, and not the
     symbol itself.

 NATIONAL WEATHER SERVICE DISPLAY - KD4UYR in FLorida had written a data base
     program that would parse National Weather Service hourly bulletins into
     APRS compatible Backup files.   After version 3.10, APRS has built-in
     commands to perform this function on line!.  See below on the details.

 OPERATOR MESSAGES - The Point-to-point message capability can be used
     for operator to operator messages and alerts.

 COMMENTS   -  Transmitted along with each position report, there is a
     short comment field which can be used to report weather conditions,
     station status, intentions or other broadcast type information.

 VEHICLE TRACKING - APRS can track the movements of any mobile with a GPS or
     LORAN receiver properly interfaced to a packet TNC.

SKYWARN APPLICATION:   The map display has the capability of presenting both
a station's position and his course and speed.  APRS recognizes a special
weather report indicator (_) so that all Wx reporting stations are highlighted
in blue and the software recognizes that their course and speed indicators are
for wind reporting and not for station course and speed.  Note that APRS does
not recognize 000 as North, but instead recognizes 360.  A value of 000 is
assumed to mean there is no wind direction available.  Other than for the
automatic ULTIMETER-II interface, the comment field can be used for a variety
of free-format weather reports which can be tailored to the conditions at any
time.  Since a manually entered WX report should retain the time that it was
valid, APRS will not update the date and time of each stations position (WX)
report unless the automatic ULTIMETER-II interface is operating.

    In addition to the weather data and comments on the Plist, the station
Beacon Text is also available for broadcasting additional amplifying info.
Any station running APRS simply calls up the LATEST display and sees the
current conditions from all stations on one screen.  Similarly, he calls up
the map display and sees the location of all stations and all specially
reported conditions.  Any authorized station can insert the location of any
special object on the map.  The location of that reported object or condition
is displayed on all screens in the network.  Even non-packet voice stations
making a weather report can be placed on the map (like an object) by another
APRS packet operator.  His station will appear similar to any other APRS
weather station, except that his report will include a marker indicating that
he was manually placed on the map by another operator.  We have used APRS on
weekends for reporting the Chesepeake Weather and Traffic net.  Load the
SKYWARN.BK file to see the APRS network during one of these nets.  Also see the
new section on how to load National Weather Service reports onto your APRS map.

NATIONAL WEATHER SERVICE HOURLY BULLETINS

     KD4UYR Kevin, in Clearwater Florida wrote a database program to crunch
the NWS hourly weather bulletins into APRS compatible BACKUP files.  He could
then load them into APRS for display on the map.  I have added this feature to
APRS in the WEATHER menu.  The GetNWS command will search the NWSposns.DAT
file for all NWS stations within the boundaries of the current APRS map
display.  If the map is larger than 256 miles, then only a radius out to 250
miles is selected to prevent overloading the L and P lists.  Similarly a
minimum radius of 32 miles is also used to be sure that at least one NWS
station is found.  The database only had NWS locations to the nearest whole
minute, so the positions are only accurate to the nearest mile or so.  This
process is my easy way of selecting the stations that you want  to display.

     The LOAD-WX-DATA command is used for loading the NWS data if available.
This command will ask you for the name and path to a text file containing the
downloaded NWS hourly reports.  This file can be obtained from most of the
commercial data servers or various BBS's.  Do not ask me where to find them...
The real WX nuts out there seem to have no trouble finding them, but in most
cases it is a pay as you go service...  APRS will then scan through the NWS
bulletin file looking for each station that you have on your APRS P-LIST.  If
it finds a matching NWS bulletin, it will parse out the Wind speed/direction,
the temperature and dew point and the barometric pressure and place these on
the P-list.  THen it will take the remainder of the report and place it in the
L-list so that you can see the raw data which includes other notes about cloud
cover and special conditions.  In both cases, the time of the entry in the P
and L-list will be the time of the NWS report (in local time).  The date is
assumed to be the current date.

     Unfortunately, these reports were designed for human reading and are also
generated by hand at all the NWS sites.  There are frequently errors or in-
properly formatted reports.  By looking at the L-List, most of these errors
can be detected.  If APRS can not make sense out of the report, it indicates
with the words "garbled report" on the P-list.  Once you have the display you
like, you can select stations on the P-list for uplink to the net as desired.
Since it is easy to generate lots of data and packets in this manner, I hope
that stations will be considerate and not overload the channel.  Once everyone
on the net sees the reports, the uplinking station should consider Quitting to
uplink in order to reduce QRM.  Once the uplinked reports are no longer valid,
the uplinking station should KILL them which will kill them from everyones
display (they will still be on everyone's P-list, however, for subsequent
display using the SHOW command).  Remember that KILL just marks them for
NOT displaying so once you KILL them, you need to continue UPLINKING the KILL
status for several beacon periods to be sure you killed everyone's version
that is on the net.

DEMONSTRATION:  To get an idea of how APRS works in a SKYWARN or other weather
reporting environment, load the backup file SKYWARN.BK using the ctrl-L
command.  The stations would normally be bright blue, but all stations fade
to gray if they have not been heard from in over 2 hours.  Use the P command
to pull up the position/weather reports and notice the format for the station
W3ADO.  That station is reporting the wind and temperature automatically
using the optional ULTIMETER-II interface.  To demonstrate the NWS capability,
center your map on FLorida at the 128 mile range and hit SHIFT-F6.  Once all
the NWS stations appear on the map, then hit ALT-N to load the sample NWS data
file provided by KD4UYR.  Look at the P and L-lists to see what is going on...

ULTIMETER-II INTERFACE:  To permit automatic weather station reporting, APRS
includes an optional serial interface to the ULTIMETER-II home weather station.
(I offered to develop one for DAVIS instruments, but they call their data
propriatary and will not share it with HAMS).  The optional APRS
WX routine is activated by a separate validation number ($9).  Once activated,
APRS accepts the serial data output of the ULTIMETER-II and puts the
information in your stations position/weather packet automatically for
unattended weather reporting.  (If you have a different home weather station
that has a serial data output, and can convince me that it is worth the effort
and widespread in the HAM community, let me know.)  The ultimeter comes in
two configurations which are not distinguishable by the user.  One version
ouputs wind in MPH and the other in KPH.  The user display can select either
units, but the serial output is always the same.  The difference is that the
MPH units begin each line with a * while the KPH units begin each line with
the # sign.  In version 4.05, APRS recognizes this difference and converts
the # units to MPH by dividing by 1.6.

RAIN VALUES:  In the Ultimeter-II, two rain count accumulators are maintained.
These are both incremented every time the rain gage clicks.  The normal gage
clicks every tenth of an inch of rain.  A special order gage clicks every
one-hundredth of an inch.  In version 4.05 APRS asks you which gage you have
so that all on the air reports are in tenths of an inch.  Since the U-II
values only have meaning if everyone knows when they were last reset, APRS
keeps a running accumulation every 10 minutes for the last hour so that it
can compute and transmit only the difference in rain for the last 60 minutes.
This way the rain reading has some meaning without prior knowledge by all
stations receiving it.  This rain/hour is intended for severe storm watches
and other interest in real-time conditions.   A reading of /R12 means that
1.2 inches fell in the last hour.  After 60 minutes, this value will return
to zero.

    After my first heavy rain fall, I came home a few hours later and of
course, the RAIN/HOUR report was then showing 0, since more than an hour had
passes since the last rain!  Obviously, this RAIN/HOUR is only good for
skywarn, so I added a Precipitation field that shows the RAIN/DAY.  This
satisfies the curiosity of the casual APRS stations that just want to see
how much rain we had during the last 24 hours.  A reading of /P16 means that
1.6 inches have fallen since the same hour yesterday.  The format we are now
using looks something like this:

   .../LAT/LONG/CSE/SPD/Txxx/Dxxx/Rxx/Pxx/Bxxx/free text comments...(auto)

   Where  CSE and SPD show the wind conditions
          /T and /D are temperature and DewPoint
          /R and /P are Rain per hour (tenths) and Rain/day
          /B is barometric pressure in inches (ignoring the leading 2 or 3)
          (auto) means it is an automatic and therefore current report
          Any field not available is not included
  
With the WX interface enabled, the normal APRS decaying of position/wx reports
is disabled and all weather/position reports are transmitted every 10 minutes.
This gives 6 reports per hour for continuity.  Of course, a WX/position report
will be transmitted by the APRS station at anytime, in response to an APRS
query; either an ALL NET Query, ?APRS, or a Wx only Query, ?WX,  or a one
station Query (by sending ?APRS in a message).  You can change the default
reporting period using the SETUP-POSRATE command.

SERIAL INTERFACE CABLE:  Peet Bros sells a serial interface cable with a DB-25
connector to RJ-11.  (Note, this is a DB-25, not a DB-9).
Since the ULTIMETER-II has no negative supply, a 5 K pulldown resistor is
added to the DB-25 connector between Pins 2 and 3.  This uses the -5 or -12
volts on the TXD line to bias the RXD line.  When I plugged in a standard phone
line connector to the ULTIMETER-II serial data output (unmarked connector on
their junction box, or side of the Display unit), I found the data output on
the green and black wire of the RJ-11.  Black is data ground, and green was
RXD.  I do not know if the wire colors are standard but they would be either
1 and 3, or 2 and 4 depending on which side is up, and the ground is the one
at the end.  The Peet Bros cable includes transient protection and RF filtering
to protect your computer as well as the bias resistor.  Remember, the
annemometer is like an antenna, high in the air.  It can radiate RFI and take
lightening charges...

REMOTE ULTIMETER-II OPERATION:  Until the ULTIMETER-II manufacturer
makes a stand alone version for remote operation, we need some mechanism to
control the transmission of U-II data on the air from a remote site without
requiring a PC computer running APRS.  During the Dayton HAMVENTION, I figured
out a way to do this remote digipeater setup so that APRS stations could
interrogate the WX conditions remotely.  Here's how:
   1) Install the U-II and a TNC at the remote site.  Install a data switch
   so that U-II data is only input to the TNC when the TNC is connected by
   either wiring to the CONNECTED LED or to the DCD line if implemented
   2) Place the TNC location in the BText using the usual APRS fixed format
   with the WX (_) symbol:    !LLmm.xxN/LLLmm.xxW_Remote U-II WX station...
   3) If the TNC is also serving as a WIDE area APRS digi, place the word
   WIDE at the beginning of the comment field so that it shows up in green,
   and include a note that WX is available.  Set MYA WIDE.  Set your UNPROTO
   path to UNproto APRS via WIDE,... (assuming there is another WIDE nearby)
   4) Set LFIgnore ON.  Set CHECK to 6 and AX25 off so that the WX connection
   will time out after 60 seconds.
At this point, any station connecting to the TNC will get the short ULTIMETER
15 character weather strings as long as they are connected.  The following
changes were made to APRS so that the connected station and all OTHER
monitoring stations could see the data.
   a) APRS now looks for the U-II data (even if not transmitted to APRS)
      so everyone on frequency sees the WX displayed, although it is being
      transmitted via a CONNECTION to only one station.
   b) The station that connected to the TNC has to be able to see the data
      also.  To enable this, he must first turn MCON ON so that he can monitor
      while connected, second, he must escape out of the APRS TALK mode so
      that APRS can process the data.  In 5.00 you can use the alt-X key
      instead of ESC to return to APRS.  Alt-X will leave your connection
      intact instead of forcing a Disconnect as it usually does.  This feature
      is not documented anywhere else, since it only is useful here for WX.
   c) As long as you are connected to the remote TNC, the U-II data will be
      transmitted about once every 5 seconds.
  
Since the remote site can also be a WIDE area digipeater, it should show the
WX circle symbol, but it will be GREEN to indicate it is also running with
the ALIAS of WIDE.  Whenever U-II data is transmitted, APRS will overwrite
the digipeater position with the Ultimeter-II WX/posit report.  The last WX
heard will remain in the P-list and on the screen until the next BText is
transmitted by the DIGI TNC.


We are encouraging the Manufacturer of the Ultimeter to make a HAM/TNC mod
so that the U-II can be connected to a remote TNC and it will only ouput
WX data once every 6 minutes or so.  If the TNC is placed in the CONVERSE
mode, these short WX reports will be transmitted.  This type of operation
will automatically update all APRS users of all remote site Weather
conditions on a periodic basis.  Until this new device is available,
however, the system described above will work and will actually provide a
more responsive display of short term weather conditions while someone is
connected.

STANDALONE REMOTE WX WITH PACCOMM TNC:  In the new PACCOMM 3.2 ROMS the same
command to permit standalone operation of the GPS MIGHT be able to be used
to make stand-alone operation of the U-II possible.  Instead of entering the
$GPGGA string as the required NMEA-0183 string, try entering just a * or a #
depending on which is the first character of your U-II WX string.  This
will tell the PACCOMM to put all after * (or#) into the LTEXT and transmit
it at the periodicity you recommend!  Now put the location of the U-II in
the normal BText and it should work!  (Let me know if it does!)


DATA LOGGING:  In APRS version 3.07, I have modified the POSITION FILTER
command so that it can be used to log weather data.  The position filter is
normally on, and it causes APRS to NOT save duplicate position reports that
are within 80 yards of a previous report.  When this filter is toggled OFF,
it reduces this filter range to 10 yards AND enables all WXstation logging.
In this mode, all WEATHER station reports are saved in a track history file.
All over-the-air reports are only received once every 10 minutes, but your own
report will be saved at the rate set by the Set-Pos-Rate command.  Note
that this did not work for your own station until version 3.10.

FINAL NOTES:  Since the WXstation option is always updating your outgoing
position report, this makes it impossible for a WX station to report a beam
heading during a Direction Finding evolution.  As of version 2.12, if you use
the BEAMHEADING command to enter a beam heading on a Fox or Jammer, then your
WX station is disabled.  To restore your WX station, restart the program.

$$$  The ULTIMETER-II is available from PEET Bros 1-800-USA-PEET (872-7338)
     for $179 plus $20 for their Serial interface cable and $60 for the
     optional rain guage (self emptying, reads in 0.1 inches) plus shipping
     of $8.25.  (For APRS, you don't need their $40 software but it is a good
     package for doing the usual home WX logging and analysis)  See adds in
     QST, CQ, Popular Mechanics, etc...

$    The optional APRS registration for the ULTIMETER-II is available from
     the author for $9 and may be ordered with APRS or as an option later.

