This is a simple Javascript calculator to compute altitude from AltAcc flight data. Along with the raw ADC values for ground and apogee you will need two other bits of information.

1) The barometric pressure as reported by a nearby station. Near both in time and distance. This value will have been adjusted to a sea level value. You can find archived data at Weather Underground. If that isn't available just use the default value provided.

2) Launch site altitude. You can find this on topgraphic maps or Google Earth.

Once you have entered the data, click on the "Calculate" button to see the results.

Ground ADC reading: counts
Apogee ADC reading: counts
Local Station pressure: kPa
Launch site altitude: feet
Launch site pressure: kPa
Offset kPa
Apogee pressure: kPa
Apogee altitude: feet MSL
Apogee altitude: feet AGL

(Note: This calculator switches equations at 36,152' as required by the NASA model so it is valid throughout the sensor range.)

You can improve the results from the Flight Analyzer program if you replace the offset. The default calibration file is named "". Use your favorite text editor to replace the offbp value with the offset shown above multiplied by 2.7. It will not be perfect but it will be better than the default value.