Dashboard Screen

The dashboard is provided to assist folks involved in tracking the balloon from the Launch Point. 

This screen has been superceded somewhat by the Flight Analysis screen.

The program requires either the pair of NMEA GPS Strings or a specific APRS string.

For GPS the balloon must be sending out $GPGGA and $GPRMC strings.

$GPGGA has the unique value of altitude and $GPRMC has the unique values of course and speed. Both packets contain time stamps and lat/long information. Naturally for the Dashboard to be really accurate, both strings need to be set by the Payload Telemetry system very closely in time (or the Balloon's telemetry system should save both strings at the same time and then send them at whatever interval your group decides best). 

You can set the size of the window for acceptable matches on the setup screen. An acceptable match means the program will consider data for all three values (Altitude, Course, Speed) as part of one data record, even if they are not stamped with the same UTC time but fall within the time set for the match. I would recommend you set the size of this window to 30 seconds or less. If there is a GPS time difference of more than 30 seconds, only a partial display will fill with data from only one GPS string. 

APRS strings vary GREATLY. Only one format is currently supported. If you wish to use this program to display values on the Dashboard you MUST use the string below. One alternate type is available in the import routine. See that page for details. Here is the required  APRS string:


This string breaks out as follows:

  • @ = string type identifier

  • 164054h = 16:40:54 UTC, the "h" on the end is IMPORTANT it flags the six digits as hh:mm:ss. You may see some strings that end in a "z". Those strings would translate as Day hh:mm or the 16th day of the month, 40:54:00 UTC (of course, you would never see 40 hours, it would always be between 00 and 23).

  • 4026.59N = 40� 26.59' North Latitude

  • / = An Icon Table Switch. It can be either a forward or backward slash for APRS to recognize it, Balloon Track cares not at all.

  • 10450.62W = 104� 50.62' West Longitude

  • O = the ascii character representing the Balloon Icon (any icon is acceptable)

  • 095 = 95� True Track Heading

  • 041 = 41 Knots Speed over the ground

  • /A = Altitude Identifier Flag

  • 020729 = 20,729 Feet Above Sea Level

Any text following by the 6 characters representing altitude is ignored by Balloon Track and processed by APRS programs as a comment string

The "Bearing - Range - Elevation" box at the bottom is all computed for the launch site as set in the active *.INI file as selected on the setup screen (or the default wbaltrak.ini loaded at startup). 

On the first line, the current UTC time is displayed. The program reads the clock in your computer and adds the value of your UTC Offset (entered on the setup screen). West Longitudes should enter a negative number (Mountain Standard Time Zone is -7). The Set Time button will set your system time. After you click it, the displayed time turns Red in color, indicating it's waiting for a GPS string. When a $GPRMC string arrives, the time and date are extracted. Your UTC Offset is applied and then the system date and time is set. Be aware, your time will be several seconds off depending on the accumulated delays in getting a timestamp from a GPS satellite through the GPS receiver, the balloon's TNC, the receiving TNC and the computer. On my system this delay adds up to about 4 seconds. But, this button is available to get your computer close so that the color coding on this display will properly function. It's not meant to be a super accurate way to set the clock. The internet or one of the NIST programs will do this job much more accurately.

On the second  line: 

  • UTC time refers to the time the GPS NMEA string was created in the GPS receiver, NOT current time. 

  • DOP refers to "Dilution of Precision". The lower the number the more accurate the GPS fix. 

  • Sats Tracked indicates how many satellites the GPS receiver was viewing when the fix was made.

  •  Mag Var(iation) is computed within GPS receivers. I use it to compute those magnetic bearings. EOSS hardly ever uses magnetic bearings. All fox hunters are trained to automatically convert to True degrees azimuth. But, different groups may find this useful. Also, launch site antenna setup might be made magnetically if you're in an unfamiliar area, and the magnetic bearings may be of help in pointing the antennas in that case.

The next two lines of the screen should require no explanation (I hope).

If you believe the data on the screen is somehow corrupted, press the RESET button and everything with the exception of Current UTC and the launch point data will be erased from the screen. It will only reappear when $GPGGA and $GPRMC arrive at the TNC.

In the launch point data you see two buttons. Click on manual entry, and you can enter any latitude and longitude for use in the computation of data in the "Bearing - Range - Elevation" box. Revert to LP, restores the latitude, longitude and altitude of the launch point as set in the current active *.INI file. If you know the decimal degrees of your launch site, you can type that information directly into the LP boxes. Also, to enter a new altitude for the launch site, you type that in directly to the dashboard screen.