Cream of the Crop 3/Cream of the Crop 3.iso/comm/aprs403x.zip/README.WX

Text File | 1994-03-15 | 17KB | 261 lines

                      USING APRS IN THE SKYWARN SYSTEM

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.
As of version 2.07 there is an optional ($9) automatic serial interface in
APRS to connect to the data 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. 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.
     As of Ver 2.08 there is a Weather (alt-W) command which 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.

 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.  In APRS version 3.08, a ctrl-A APPEND
     command was added so that these files could be loaded in without destroying
     the existing P and L lists.  Now in APRS version 3.10, APRS has built-in
     commands to perform this function.  See the section 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.  To date, I have not
standardized on the comment field, other than for the automatic ULTIMETER-II
interface.  This leaves the whole field open for a variety of Weather
reporting needs in free-format so that weather reports 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 use APRS every
weekend 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.  In version 3.10, I have added
this feature to APRS.  The shift-F6 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 alt-N command is the command 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 would be happy to develop one for the DAVIS instruments, but they consider
their data formats to be propriatary and will not share).  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 rain report from the
ULTIMETER-II is an accumulated value since the device was last cleared.  In
APRS version 4.02, the count is zeroed every hour, so that the rain field
as transmitted is the report for the last hour.  The total accumulation has
a separate field labeled /PXXX for total precipitation.  Therefore, I had
to rename the Barometric pressure field to be /BXXX vice /PXXX.  In order for
this total accumulation value to have any meaning, all stations in an area
need to agree on when this counter is reset in all U-II's in the net.  The
format we are now using looks something like this:

   .../LAT/LONG/CSE/SPD/Txxx/Dxxx/Rxxx/Pxxx/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 (hundredths) and total Accumulation
          /B is in millebars (ignoring the 4th character)
          (auto) means it is an automatic and therefore current report

With the 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 (ctrl-Q), or a Wx only query (^W), or a one station
Query (by sending ?APRS in a message).

SERIAL INTERFACE CABLE:  Peet Bros sells a serial interface cable with a DB-25
connector to RJ-11.  (Note, all of my computers use a DB-9 connector for the
serial port so the DB-25 is of marginal utility for most modern computers).
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 SENSORS:  Another advantage of the APRS system is the ability to
display information from remote environmental sensors.  We gave up building
our own sensors and are hoping to use the ULTIMETER-II home weather station
as an add on to all remote APRS digipeaters (without a PC).  Unfortunately,
however, we have not come up with a way to only transmit the data once every
10 minutes without having another microporcessor to parse the serial stream
from the ULTIMETER-II and only send it to the TNC once every 10 minutes
instead of the once every 5 seconds.  A simple edge triggered timing circuit
will not work because each 15 character record is often interrupted, even
between characters with significant time delays so that a simple once every
10 minute timer circuit is not suitable.   (NOTE!  PEET Bros is working on a
standalone version of the ULTIMETER-II which can be configured to output its
WX conditions once every 10 minutes.  This can then be directly connected to
a TNC for remote transmission of WX conditions.  When this modified U-II is
available, the WX data will go out as a UI frame and APRS will grab it and
display it.  The position data will be stored in the TNC BText.  These
stations will appear on the map in Blue and their reports will be visible
using the LATEST display just like for the home stations.  It is planned to
place an ULTIMETER-II node at the location of every WIDE area digipeater used
in the APRS system.  Currently weather nodes are under construction in Maryland
at Point Lookout in the south, Patuxent Naval Air Station, Chesapeake Beach
division of NRL, Annapolis, Baltimore, and NorthEast.  These sites will not
only provide automatic weather reporting capabilities all along the Chesapeake
Bay area, but will also form the backbone network for reporting the movement
of radio amateur's boats with GPS and LORAN.  Load the SKYWARN.BK file.

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 (alt-S).  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 ctrl-B 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 interface routine for the ULTIMETER-II is available from
     the author for $9 and may be ordered with APRS or as an option later.