WX.TXT            USING APRS IN WEATHER AND SKYWARN APPLICATIONS
Document version: 8.6.7 26 Jul 2004.  (Previous was 8.3.5 of 10 Mar 99
Author(s):        Bob Bruninga, WB4APR <bruninga@nadn.navy.mil>
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

New: Putting raw PEET Bros WX packets on the air is no longer encouraged.
     It is better to use one of the little PIC's to convert to standard
     APRS format so that all the Mobiles and HAM HUD's can see the WX

New in 809  Now supports COUNTY WX Warnings.  See sections below
New in 796  Supports HC/TS winds to the DOT symbol too for predicts
New in 793  *****  All new WX formats not Backward compatible *****
              WX-GETmetar can load METAR data from a file into P-LIST.
New in 78b  File-Print will log new data to a printer and on the P-LIST,
              Just-Print-WX will print a file or page of all WX data
              Fixes receipt of remote Ultimeter WX data for some units

OVERVIEW:  APRS is an ideal tool for reporting weather conditions via
packet when its second serial port is connected to a PEET Bros ULTIMETER
or DAVIS home weather station.   APRS is idealy suited for SKYWARN
with the following features:

 MAP DISPLAY - Shows the location of all WX stations and WX objects

 WX SYMBOLS - Dozens of WX symbols that will even move if given a CSE/SPD

 WX WARNINGS - You can mark large areas with either rectangles, circles,
     triangles, or lines using the OBJECTS-AREA symbols.  New in 809,
     Whole counties will change color based on WX Warnings transmitted
     by specially formatted APRS Messages.  See COUNTY WARNINGS below.

 WEATHER ONLY - The JUST-WX command for a temporary display of only WX
     stations on the map or P-List.  Use the WX-JUST-WX-ALWAYS command
     to lock this feature on and off.  The N-NEXT command cycles through
     each WX station in turn with a circle on the map and displays its
     wx conditions at the top of the screen.

 TROPICAL STORM WINDS - a special format causes APRS to color huricanes 
     red, tropical storms yellow and depressions blue. It will also show 
     the radius of the winds with colored circles offset in the direction 
     of the danger quadrant proportional to the storm speed of advance.

     DDHHMM/LAT/LONG@CSE/SPD/TS/www^GGG/ppp>RRR&rrr

     Where @   is the symbol for a Huricane
           /   is the symbol for a predicted posit
           CSE is direction of movement
           SPD is speed of movement
           TS, HC and TD are types of storm
           www is sustained wind speed
           GGG is peak wind gusts
           ppp is central pressure
           RRR is radius of Hurrican winds
           rrr is radius of TS winds

 DEAD RECKONING -  APRS dead-reckons moving objects, so the symbol on the
 map is presented where it SHOULD be, NOT where it was when first reported.
 After two hours with no update, the symbol fades to dark gray.

 NWS STATION PLOTTING - Hit MAPS-OVERLAYS-NWS to see all NWS Sites

 METAR BULLETINS - Suggested by KD4UYR in FLorida, this feature parses
     NWS METAR bulletins and plots the WX data on the map.
     (removed from APRSdos in 837)

 WX-DISPLAY - You may display WX conditions instead of callsigns on maps:
           WX-DISP-TIME shows the TIME
           WX-DISP-TEMP shows Temperature
           WX-DISP-BARO SHows Baro and rain
           WX-DISP-WIND Shows winds

 OPERATOR MESSAGES - APRS messages are ideal for Skywarn traffic.
     With FILE-PRINT enabled, these messages and WX reports can be 
     scrolled to the printer.

 STATUS - In addition to weather data included in position reports, the
     station STATUS packet is also available for additional info. 
     
 BULLETINS -  Bulletins are an alerting mechanism for all stations.

 VOICE REPORTS -  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 in purple showing that his report
     has been placed there by another station.


COUNTY WARNINGS - APRS can color in counties based on NWS Warnings.
Hit the usual label zoom keys ] and [ to see the county name if needed.
The formats for these warnings are a message sent to the APRS address of
NWS-XXXXX as shown below.  These messages accumulate on the APRSdos
TRAFFIC page where they drive the coloring algorithm.

    NWS-WARN :exptime,type,c1,c2,c3,c4,c5, (where c1-c5 are counties)
    NWS-WATCH:exptime,type,c1,c2,c3,c4,c5,
    NWS-ADVIS:exptime,type,c1,c2,c3,c4,c5,
    NWS-TEST :exptime,type,c1,c2,c3,c4,c5, (trailing comma is needed)
    NWS-CANCL:type,c1,c2,c3,c4,c5,

Where: exptime - is the Expiration time in the usual DDHHMM format
       type    - is free text of the type of warning
       c1 - c5 - 1 to 5 counties truncated to 9 bytes or less each

NOTE:  If the type of warning is longer than 10 bytes, then only include
4 counties per line to prevent truncation by APRS on receipt.

In APRSdos, maps with county map labels of the form SS_COUNTY which
match the counties in the C1 to C5 fields above will change color.
These fields are limited to 9 characters according to these rules:

    1. SS_ is the state abbreviation
    2. Next 6 chars must be first six chars of County name, omit
       spaces and abbreviate SAINT to ST, PRINCE to PR, etc...

See COUNTIES.TXT for details in making the labels for your maps.
Since there is not room for all 3000 Counties in my larger regional
and USA maps, in these maps, the entire state will color based on the
SS_ formats.  Or you can trigger a whole state with SS_STATE.


NATIONAL WEATHER SERVICE HOURLY METAR BULLETINS
*** This capability was removed in 8.3.4 to make more room ***
It was retianed in the APRSwx.exe version.

Based on work by KD4UYR in Clearwater FL, the MAPS-OVERLAY-NWS command
searches the NWSposns.POS file and temporarily displays all NWS stations
within the boundaries of the current APRS map display (up to 250 miles).
You are given the option of a one-time map overlay or to add the sites to
your P-LIST.

The WX-GET-METAR command is used for loading a file of NWS METAR
reports.  This file can be obtained from most of the commercial data
servers or some BBS's, or on the internet at:

     http://weather.noaa.gov/weather/metar/shtml

APRS will scan the NWS METAR file for each station on your P-LIST.
For each match, it will parse the Winds, temp, dew point and pressure
onto the P-list and places the rest of the report on the L-list.  The
packet times 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.

Once the data is loaded, you can uplink selected stations to the APRS net
as desired.  Once everyone on the net sees the reports, the uplinking
station should consider Quitting the uplink in order to reduce QRM.

DEMONSTRATION:  To see how APRS works in a SKYWARN or other reporting net,
load the backup file SKYWARN.BK using the FILES-LOAD command.   To
demonstrate the NWS capability, center your map on Illinois at the 128
mile range, enter the MAP-OVERLAY-NWS command and select the Add option
to add them to your P-List.  Next, enter the WX-GETmetar command to load
the sample METAR data file.  Look at the P and L-lists to see what is
going on...

METRIC MEASUREMENTS:  Select wind speed in KPH and temperature in
Celsius by toggling the WX-METRIC command.   Make this permanent, by
saving a CONFIG file.  The on-air APRS WX protocols, however, still
will be in MPH and F.  Also, the ALARMS are compared to MPH and F values.

WX ALARMS:  If a WX report comes in that exceeds your WIND, TEMP or RAIN 
alarm values, the station is plotted in RED and an ALARM sounds.  This 
can be used to warn of the passing of a warm or a cold front.  

CLEARING ALARMS:  When an alarm occurs, the station is drawn in RED and
the map is re-drawn to center on that station.  Also, the station is
marked on the P-list with the ALARM marker.  TO clear the alarm, simply
hook the station on the map, and then UNhook it (hit ENTER twice), or
use the WX-ALARMS-CLEAR command.  To clear the A on the P-list, hook the
station and hit the A key.  Normally, the ALARM on the P-list will only
sound if that station MOVES.  Since a WX station should not move, there
is really no problem in leaving the A on the Plist until convenient to
remove it.

WEATHER WARNINGS AND WATCH BOXES:  You can use the OBJ-AREA-LINE command
to draw a box from 400 feet to 400 miles plus-or-minus X miles from a 
line between points A and B.  The line and width are perfect for WATCH 
and WARNING boxes.  Use the normal INPUT-ADD-AREA-LINE command prompts
which will indicate the +/- sidelines in a 3 digit number of Miles 
enclosed in braces {075} anywhere in the COMMENTS field.

HOME WEATHER STATION INTERFACE:  With 2 serial ports, APRS can insert
the ULTIMETER or DAVIS conditions in your position report.  ULTIMETERS
that output data with a * output wind in MPH and those with a # in KPH.
APRS averages the wind value over the last 4 samples, so the default
rate is every 15 seconds to yield a running 1 minute average.

RAIN VALUES:  Rain is counted in increments of 0.1 or 0.01 inch or 1mm.
but reports all values in 0.01 inches over the air.  Since raw rain
counts have no meaning without knowing when they were last reset, APRS
only compares the difference in rain for the last hour (rXXX) and the
precipitation in the last 24 hours (pXXX).  A reading of r123 means 1.23
inches fell in the last hour.  After 60 minutes, this value will return
to zero.  A reading of p164 means 1.64 inches have fallen since the same
hour yesterday.  For REMOTE ULTIMETERS with only a TNC and no PC,
the P value means rain since MIDNIGHT and an uppercase Pxxx is used.
Also since there is no RAIN per hour value, that field is replaced with
the raw rain counter #xxxx.

FORMATS:  APRS re-formats data from attached WX units and transmits the 
data as shown below.  For remote Ultimters, where there is no PC, the 
TNC just transmits the raw data, but APRSdos converts them to these formats
for display on the P-LIST.  (In the future we want to minimize these
raw packets since they cannot be decoded by all stations).

   _CSE/SPDgXXXtXXXrXXXpXXXdU-II        Original U-II auto
   _CSE/SPDgXXXtXXX#XXXdU2r                  Original U-II remote
   _CSE/SPDgXXXtXXXrXXXpXXXbXXXXhXXdDvs  Davis WX station
   _CSE/SPDgXXXtXXXrXXXpXXXbXXXXhXXdU2k  U-500/2000 with APRS
   _CSE/SPDgXXXtXXXPXXXbXXXXhXXdU2kr      Remote Ultimeter Logger
   _CSE/SPDgXXXtXXX#XXXbXXXXhXXdUpkm      Remote Ultimeter Pkt Mode

   _CSE/SPDgXXXtXXXrXXXpXXXPXXXhXXbXXXXX%type NEW FORMAT APRS793 June 97
                                              NOT BACKWARD COMPATIBLE

Where:        
  CSE/SPD is wind direction and sustained 1 minute speed
  t is in degrees F
  r is Rain per last 60 minutes
  p is precipitation per last 24 hours (sliding 24 hour window)
  P is precip per last 24 hours since midnight
  s is snow
  b is Baro in tenths of a mb
  h is humidity in percent.  00=100
  g is Gust (peak winds in last 5 minutes)
  # is the raw rain counter for remote WX stations. See notes on remotes
    % shows software type d=Dos, m=Mac, w=Win, etc
    type shows type of WX instrument


With the WX interface enabled, the normal APRS decaying of position/wx
reports still holds as long as nothing changes (except the wind).  If any 
other WX value changes, then the period is reset to the alt-SETUP-POSrate 
value.  The WX-WIND command can be used to set a Wind threshold which will 
force a WX report whenever the wind is above that threshold.

WX PERIOD:  APRS decays to 10,20,or 30 minute rates depending on the
number of digipeaters.  For a weather station, you should change the
MaxPeriod to maybe 10 minutes or so using a text editor in your
CFIGxxx.APR file.  There it is expressed in seconds.  Of course, a
WX/position report will be transmitted by the APRS station at anytime,
in response to an APRS or WX query.

ULTIMETER INTERFACE CABLE:  Peet Bros sells an interface cable with a
DB-25 connector to RJ-11.  Since the U-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 unused TXD line to bias the RXD
line.  You can use a common phone line plug for their serial output.
I found the data on the green while using the black wire as ground.
If your connector was crimped on backwards, red is data and yellow is
ground.  The Peet Bros cable includes transient protection and RF
filtering to protect your computer as well as providing the bias resistor.
Remember, the annemometer is like an antenna, high in the air.  It can
radiate RFI and take lightening charges...  The U-2000 is directly
RS-232 and needs no pull down resistor.  Be sure the U-500/2000 is in
DATA-LOGGER mode.

DAVIS INTERFACE:  You must have the DAVIS Weather Link serial interface
option before your Davis station will output serial data.  Simply connect
their connector to your PC. You MUST use the APRS alt-SETUP-OTHER-AGL
command to set your average ground level.  This converts your baramoter
readings to their equivalent value at sea level...  Your objective is to
find an exact AGL that will result in your BARO readings matching the
readings on your instrument or local NWS.  THis AGL will probably NOT be
your true AGL.

SAVE A COMM PORT!  You can use a simple 89 cent switch to allow other
devices to share a single COMM port with your WX station.  Since the WX
stations only use ONE pin and GROUND, simply add them to your MODEM
cable with a simple SPDT switch as follows:

  ULTIMETER-II   >---------*--------*  sw1
                           |        <----*--------------> RXD
  MODEM   }      >------------------*
    or    }                |
  other   }                *-----/\/\/\/\-------*
  serial  }                        5.6k         |
  device  }      <------------------------------*-------< TXD
          }      * * * -----------------------------* * * other pins
          }      *--------------------------------------* GND

Actually, you can wire this to any serial device that you do NOT use while
running APRS.  I chose my MODEM that is on COM2.  Note the series resistor
as mentioned in the text to provide the -V pull-down for the U-II output.

REMOTE ULTIMETER OPERATION:  Only the Ultimeters from Peet Bros can be used
as remote WX stations using only a TNC and a radio.  This is because they 
output continuous data without needing a PC to interrogate it periodicaly.  
There are two ways to time the transmission of this data for the packet 
channel depeneding on what Ultimeter you are using.  We call these PACKET 
mode or DATA LOGGER mode (though neither of these modes is now recommended).

DATA LOGGER MODE (GPS mode):

  U-II - These units output 14 bytes continuously beginnning with * or #
  U-2000 (old) - These units output 44,48,or 52 bytes beginning with !!

For the DATA LOGGER mode, the TNC must do the scheduling of packets just
like the TNC does for continuous GPS data.  Just program your TNC to 
think that the WX data is GPS data by entering the #, * or !! instead of the
usual $GPRMC data typically used for GPS.  Then set the timing for each
transmission to be about once every 5 minutes.  Be sure to SET ECHO off if
your ULTIMETER-II uses a resistor on the TXD line to bias the RXD line!
(Otherwise you will echo all heard packets back onto the channel!  KD4GOE
figured that one out!).

PACKET MODE :
  U-500 - Outputs 44,48,or 52 bytes beginning with $ULTW

This mode was designed for APRS packet since the WX unit only outputs
a single data line every 5 minutes.  Since it is already timed to once
every 5 minutes, all the TNC has to do is be in UI CONVERSE mode and it
will send the packet.  Be sure to use a TNC that can be configured to
power-up in UI-CONVERSE.  Try UIMODE or PMode-CONV depending on your
TNC.  ALso you must set LFIgnore to ON so that the LF after the CR is
not transmitted..  Since the Kantronics TNC's do not have LFIGNORE,
you must set SENDPAC to $0A (linefeed) and set CR off!  If there are
dozens of REMOTE U-500's, hopefully their clocks are staggered enough
that they wont all transmit at EXACTLY the same time.

CAUTION:  Only U-500's and only U-2000's manufactured after April 97
should be used in packet mode.  U-2000's prior to that date will not
show wind in the packet mode.  And these days, raw WX packets on
the main APRS channel are not reeommended.


WX POSITION:  In both cases, you must put the unit's POSIT in the BText
using the "_" WX symbol.  This way the TNC transmits two packets, one
is a BText WX posit with no WX data, and the other is raw WX data with
no posit!  APRS cannot display the WX on the map until it has received
a WX posit beacon.  So, set the beacon to go about once every 20 minutes.
Once the posit is received it will be displayed as a Blue dot unless the
site is also acting as a WIDE-RELAY digipeater, and it will show GREEN if
the delimiter between the LAT/LONG is set to a backslash instead of the
usual forward slash.

WX LOGGING:  Use the WX-LOG command to turn WX-LOGging on and off.  It will
show on the control panel when on.  If ON, then on-air reports are saved
when received every 10 minutes or so, and your own report will be saved at
the rate set by the Set-Pos-Rate command.
