High Voltage Shareware/high1.zip/high1/DIR18/APRS307B.ZIP/README.WX

Text File | 1993-12-12 | 12KB | 185 lines

                      USING APRS IN THE SKYWARN SYSTEM

     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.

 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 ther 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.  CAUTION:  Since a manually entered WX report should
retain the time that it was valid, but APRS updates the time of each stations
position report when transmitted, I have added a routine to look for the word
(manual) at the end of a weather report.  If these characters and the brackets
are found in the POSIT comment field, then the DATE-TIME fields will NOT be
updated, so other stations know when the noted conditions were valid.

    In addition to the brief weather report, 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.

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.

ULTIMETER-II INTERFACE:  To permit automatic weather station reporting, APRS
includes an optional serial interface to the ULTIMETER-II home weather station.
(I hope to develop one for other WX stations too).  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 for the present day, but  I hope to modify APRS to convert
this to the rain fall in the last hour.  I think this is more representative
for the typical emergency storm watch scenario that HAM radio is used for.
If you think of a better way, tell me.  I am not a weather fanatic and do not
have first hand information of the needs of ARES or SKYWARN.  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.  This makes any position report that
differs only by .01 in Latitude or Longitude be saved as a new position.  In
this mode, all WEATHER station reports including your own are saved in a
track history file.  All over the air reports are only transmitted once every
10 minutes, but your own report will be saved at the rate set by the Set-Pos-
Rate command (alt-S).

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)  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.