Overview Type-A QTH Information, Temperature Type-B Precipitation, EMP Type-C Wind, HAAT of Anemometer Type-D Barometric Pressure, Humidity, inside readings Type-E Background Radiation
The extended data packets are used for full data exchange with other WXN servers over APRS1. This overcomes the severe lack of weather data native to APRS. The transmission of these packets takes place at an interval determined by the broadcast of the AprsExtraText packets and is offset and delayed dynamically based on channel activity and the setting of AprsDelayThreshold in the wxnaprd.conf file.
The extended data format uses the APRS User-Defined Data Format as described in the APRS Protocol Reference, Protocol Version 1.01, chapter 18. This document can be found at the TAPR web site http://www.tapr.org.
Information is grouped by related data types.
Values are comma delimited and set apart into groups by the '/' character. The length of each packet will vary between 60-90 bytes depending on actual data values. Temperature units are in degrees Fahrenheit, wind in MPH, barometric pressure tenths of millibars, precipitation in hundredths of an inch, time is hh:mm, wind direction in degrees relative to true north.
Packets can be received in any order after the initial APRS native data is received. If a native wx data packet has not been received, the extended data packets are ignored. The state-county FIPS plus the city in the type-A packet is used to look up the exact coordinates from the compiled geographic database used by the server or from user supplied information in the aprsqth file. The geographic database is based on USGS/USDOT data. Received APRS position reports will override any of the above.
No empty fields are permitted. Numeric fields that are not used must be filled with '0', '0.0', '0.00', or '00.00' (without the single quotes) depending upon the type. Only negative values are preceded by the sign of the number. Empty time values must be expressed as '--:--' (without the single quotes). Empty strings are filled with a single '*' (again, without the single quotes).
Data: QTH, alias, temperature
APRS Header: {Wa
QTH: State-County FIPS code, City
Example: 18163,Evansville
Alias: Node Alias
Example: EVVWXN
Temp1: now, hi, hi time, low, low time, hr rate, 24hr rate
Example: 83,87,14:13,63,03:00,-4,2
Temp2: yesterday high, yesterday low, soil temp
Example: 85,62,73
Example of complete information field in the packet, including APRS header and group separators:
{Wa18163,Evansville/EVVWXN/83,87,14:13,63,03:00,-4,2/85,62,73
Data: precipitation, EMP (lightning)
Note: Precip values are in expressed in hundredths of an inch
APRS Header: {Wb Precip: total since midnight, inst rate, hr rate, last hr, 24 hr, yesterday, month, year
Example: 14,0,0,5,62,76,415,2078 EMP: 5 min, 15 min, 30 min, 60 min, day totals
Example: 15,42,69,97,1050
Example of complete information field in the packet, including APRS header and group separators:
{Wb14,0,0,5,62,76,415,2078/15,42,69,97,1050
Data: wind
APRS Header: {Wc
Wind: avg spd/dir, gust spd/dir, avghi spd/dir/time, avglo spd/dir/time, gusthi spd/dir/time
Example: 10,260,20,270,13,236,01:44,10,236,17:10,20,225,01:44
HAAT: Height in feet of wind anemometer assembly above ground level
Example: 30
Example of complete information field in the packet, including APRS header and group separators:
{Wc10,260,20,270,13,236,01:44,10,236,17:10,20,225,01:44/30
Data: barometric pressure, humidity and inside temperature/humidity
Note1: if none of these sensors exist, the packet will not be transmitted.
Note2: Barometric pressure is expressed in tenths of millibars.
APRS Header: {Wd
Barometer: now, hi, hi time, low, low time, hr rate, 24hr rate
Example: 10132,10132,17:19,10020,01:01,-68,-10
Humidity: now, hi, hi time, low, low time, hr rate, 24hr rate
Example: 63,82,06:44,59,16:12,-5,7
Inside: temperature, humidity
Example: 72,56
Example of complete information field in the packet, including APRS header and group separators:
{Wd10132,10132,17:19,10020,01:01,-68,-10/63,82,06:44,59,16:12,-5,7/72,56
Data: background radiation
Note: if the sensor does not exist, the packet will not be transmitted.
APRS Header: {We
Background Radiation: now, hr avg, day avg, max, alarm count,trip-point
Example: 12,12,15,17,0,27
Example of complete information field in the packet, including APRS header and group separators:
{We12,12,15,17,0,27
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