Flight Analysis

During a flight you may be interested in the most recent APRS or GPS information sent down via packet radio.

Clicking on the buttons lower right:

  • MapPoint Track opens the Map display of the track

  • Scan Map opens the user scanned map display

  • mm:ss button changes the display to minutes and seconds. In the above example the display would change to 70:00

  • Click on the Switch to Grid button and the latitude and longitude values would be replaced by Grid References as related to the grid origin you specified on the setup screen. (the labels Latitude and Longitude would be replaced by Grid X, Grid Y

  • AutoChart On indicated each new packet will automatically be displayed. Click on this button and the charting does not update with each packet. However, data is still being captured and when you return the chart to Autocharting On, all data will be displayed.

  • Close closes the form. Data ceases to be captured for this display.


The Chart displays the history from first packet received to the last packet received. The chart is labeled with the current setting and the button is highlighted. You can chart:

  • Altitude

  • Ascent Rate

    • for the last two packets

    • the average of the last 5 packets

    • the average for ALL packets

  • Speed

    • for the last two packets

    • the average of the last 5 packets

    • the average for ALL packets

  • Range

  • Ground Track plots a low resolution X, Y  track of the latitude and longitude.

  • Course

    • for the last two packets

    • the average of the last 5 packets

    • the average for ALL packets

Select the different intervals from the Menu "Chart Settings". 

Below the Chart is a text readout of some of these same values.

The values for the chart and the readouts below it are CALCULATED values. 

The speed and ascent rate are calculated by determining the actual distance covered divided by the time. This is unlike the speed reported for the current packet which is just a snap shot of what GPS is seeing at that time.

Values for the ascent text box are calculated from the first packet to current packet. When a burst is detected, they are reset to display Descent values (the caption on the text display is changed to reflect that) and are calculated from the last (highest) packet prior to burst to the current packet. Since the 5 packet average is "dormant" for the first few descent packets, the word "burst", as shown above, is displayed instead.

This screen is updated each time a valid position fix is received. 

Most Recent Data

Data from the last packet is displayed in the box at the right of the screen. This includes:

  • Time Stamp - This is the time associated with the APRS or GPS packet received NOT the time it was received on your computer.

  • Altitude - As reported by GPS

  • Elevation - The degrees above the horizon from the Home (Launch) station.

  • Course - This is the course as reported by the GPS NOT a calculated value. See note.

  • Speed - This is the speed as reported by the GPS NOT a calculated value. See note.

  • Range - Between the Launch Site and the Balloon. This is distance between the Launch Site and the point on the GROUND directly below the balloon, not the actual slant distance between the Launch Site and the Balloon in the air.

  • Bearing - The azimuth in degrees from the Launch Site to the Balloon

  • Latitude and Longitude - The balloon's current lat/long.

  • The Grid X/Y position - you can see either Lat/Long or Grid the latitude and longitude above would be replaced by grid positions and the labels for those boxes would be changed to Grid X, Grid Y

  • Elapsed time from first received packet to most recent in either minutes and seconds or hours, minutes and seconds. Click on "mm:ss" to switch back and forth.

NOTE: GPS Course and Speed. This data is found in the GPRMC string. Many folks fly with only the GPGGA string, or they infrequently transmit the GPRMC so, if no RMC strings arrive, these fields will remain empty. If RMC strings are received intermittently then the last value will be displayed. Balloon Track calculates the course and speed by comparing packet location reports. It is probably the most reliable data as it shows the average speed and direction the balloon traveled between the last two packets received.

When building the data for these charts, I do NOT use the launch site location as the first data point. However, it can be included if you wish. Click on Chart Settings and click on Include Launch Point Data. There is however, a slight problem. I do not know when you launched your balloon. So, for the first four packets received you may get some slightly strange readouts for some values. Once the 5th packet is received, the program extrapolates a launch time and starts using that information in the calculations. Things smooth out nicely then.