APRS Formats used in EOSS

General Info

For info on how to track the flight live click here.

One word of warning. The paths and addressees may change for any of these payloads for any flight. The data layout will remain the same.

For the full low down on how the APRS format works download the APRS specification from the Tucson Amateur Packet Radio Site:

http://tapr.org/aprs_working_group.html

AE0SS-11 GPS/APRS package

(maiden flight ~ EOSS-039 - formerly W5VSI-11 for 40 or so flights)

This package beacons out standard NMEA strings for position information. These strings are broadcast periodically along with a KPC3+ telemetry string:

  • T#xxx = the xxx indicates the telemetry frame number. Telemetry decoding algorithms.

  • $PRWIZCH

  • $GPRMC

  • $GPGGA

Most APRS programs can read these strings and plot positions.

AE0SS-11>BEACON:T#087,086,101,046,136,135,00111000
AE0SS-11>APRS:$PRWIZCH,30,7,05,7,02,7,04,6,10,7,06,7,29,2,21,7,00,0,13,6,00,0,00,0*42
AE0SS-11>APRS:$GPRMC,151447,A,4034.5189,N,10424.4955,W,6.474,132.5,220406,10.1,E*58
AE0SS-11>APRS:$GPGGA,151449,4034.5163,N,10424.4937,W,1,06,1.41,21475.8,M,-21.8,M,,*4D

For a full description of each string go to the NMEA FAQ page.

The $PRWIZCH string is a Rockwell proprietary string that indicates which satellites (PRNs) are being used in the fox

KC0YA-11 GPS/APRS package

(maiden flight EOSS-101)

This package beacons out standard NMEA strings for position information. These strings are broadcast periodically along with a KPC3+ telemetry string:

  • T#xxx = the xxx indicates the telemetry frame number. Telemetry decoding algorithms.

  • $PRWIZCH

  • $GPRMC

  • $GPGGA

Most APRS programs can read these strings and plot positions.

KC0YA-11>BEACON:T#146,208,135,124,038,134,00110011
KC0YA-11>APRS:$PRWIZCH,04,7,05,7,00,0,21,0,00,0,30,7,06,7,13,2,10,7,02,7,00,0,00,0*49
KC0YA-11>APRS:$GPRMC,145322,A,4034.3765,N,10410.8083,W,12.062,220.7,220406,9.9,E*56
KC0YA-11>APRS:$GPGGA,145324,4034.3714,N,10410.8151,W,1,06,1.46,21869.4,M,-22.1,M,,*47

For a full description of each string go to the NMEA FAQ page.

The $PRWIZCH string is a Rockwell proprietary string that indicates which satellites (PRNs) are being used in the fox

Rocky Mountain Radio League
Cross Band Repeater

The RMRL Cross band repeater outputs APRS strings for position location.

We have switched to a new format APRS string. While it is a little harder on the eyes if you are trying to decode it "manually", if you are using APRS it should prove quite useful. We are particularly interested in obtaining accurate time stamps and this new format brings that capability. Post flight analysis should prove much more accurate.

W0WYX>APRS:@164428h4029.84N/10427.34WO234/038/A=092748

  • The leading 164428 is time and breaks out as 16:44:28 UTC. This is the time stamp from the GPS string that provides the latitude and longitude.

  • Latitude: 40� 29.84' North

  • Longitude: 104� 27.34' West

  • The "O" following the "W" in the longitude is the symbol representing an icon for a balloon.

  • 234 following the "O" balloon icon symbol is a 3 digit number representing the course as reported by the onboard GPS (true)

  • 038 is speed in knots

  • /A=092748 represents the altitude, in this case 92,748 feet above sea level

Here is a sample text file that simulates a flight in the new format. It might prove useful for preflight testing.

The old format just contained latitude, longitude and altitude:

W0WYX>APRS:!4029.84N/10427.34WO Alt = 92,748 Feet.

This string translates to:

  • Latitude: 40� 29.84' North

  • Longitude: 104� 27.34' West

  • The "O" following the "W" in the longitude is the icon for a balloon.

  • And altitude is obvious

K0YUK-11 APRS System

K0YUK-11>APT310:/132252h3857.77N/10434.12WO052/014/A=009628/EOSS-84 Balloon

This string breaks out in the same manner as the W0WYX repeater's output with two exceptions.

The first change is the initial character in the information part of the packet. This APRS string begins with a forward slash "/", while the W0WYX repeater begins with an at sign "@". These two characters indicate a very slight difference in the packet's possible contents. They both say, here is an APRS packet with a time stamp. However the "/" packet says, "I don't have APRS messaging capability so don't try to use me for that" while the "@" indicates that, the packet station does accept APRS messaging

The second change occurs after the altitude where the K0YUK system has the balloon's flight designation added. Including the preceding slash, "/EOSS-84 Balloon" is entirely a comment string and is NOT part of the APRS data format.
 

K0ANI-11 APRS System

K0ANI-11>APRS:@162944h3857.22N/10434.14WO124/013/A=009147 Ft.

This string breaks out in the same manner as WYX above. In this case the space and Ft. following the altitude are comments and NOT part of the APRS specification.