CSV Flight log format

Every flight you save is written as a CSV file, a plain text table you can open in any spreadsheet program or read with your own code. This page describes that format in detail. It covers a Revision 4 or later board, which records the full set of motion data; a Revision 3 or earlier board uses the same layout with the motion columns left out, and there is a note on the differences at the end.

The whole file, the header and every reading, is the cleaned True Path result, and it is signed so it can be checked for tampering. There is more on those on the True Path and apogee page and the security page.

The file has three parts, in this order:

First comes a header of fourteen rows holding a summary of the flight and the exact conditions and settings it was recorded under. Then a single blank row. Then one row of column names, followed by the flight data itself, one row per recorded sample. In other words the header takes up sixteen rows, and the readings start on row seventeen.

The header is arranged as label and value pairs sitting side by side in columns, so it reads tidily when opened in a spreadsheet: a pair on the left, a pair in the middle, and on Rev4 and later a further pair on the right carrying the motion related figures. If you are writing a parser, the simplest approach is to read the header rows for the fields you want, skip the blank row, and treat everything from the column names onward as the data table.

The header carries everything you need to understand the flight without reading a single data row. The fields fall into a few groups.

The flight summary gives the apogee in metres and the time it happened, the landing height and time, the maximum upward velocity, the landing velocity, and the average samples per second. The identification fields are your device tag, your competitor tag, and the altimeter's serial number, which are the details you use to add a flight to your account at altimetercloud.com.

The conditions and settings cover the sea level pressure and static temperature used to work out height, whether sensor temperature was used, the board temperature at the start and end of the flight, the battery voltage at the start and end, the firmware version, the board revision, and a number of individual settings such as orientation, launch protection, hybrid mode, sample speed and recording stop. There is also a single Settings string field that packs the complete configuration used for the flight into one line, and an Adjusted log field that reads "no" for an original flight and tells you if the log has since been re-derived with different pressure or temperature.

Because the Settings string is written in shorthand, here is what each key holds. The configurable ones match the options described on the settings page.

Finally the verification hash is the HMAC-SHA256 signature that lets Altimeter Cloud confirm the file has not been altered. On Rev4 and later the right hand side of the header adds a set of motion statistics: burnout and ejection times, burnout and descent velocities, the maximum and average accelerations during ascent, descent and the burn, the launch pitch, roll, yaw and tilt, the dominant axis, and timing details.

After the blank row and the row of column names, each row is one recorded sample. The columns appear in this order:

A couple of things are worth knowing. Time is measured from launch, so launch is zero; because the Nano keeps a short buffer of samples from just before lift off, the first few rows can show small negative times. The acceleration and gyro axes are the board's own axes, which line up with the rocket according to your orientation setting. There is one row per sample up to the maximum you set, so a full log can be tens of thousands of rows.

A short example using real flight data, showing the column names and a few rows from around the moment of launch:

Time(ms),Altitude(m),Velocity(m/s),acceleration_x(mG),acceleration_y(mG),acceleration_z(mG),acceleration_total(mG),gyro_x,gyro_y,gyro_z,Board temp(C),pitch,roll,yaw,tilt
-10,0.085,4.54,-993,35,76,-3.5,376,-12,-68,,3.40,-26.21,38.18,26.41,
0,0.141,5.76,-994,37,74,-2.6,330,-22,-74,,1.63,-26.97,35.28,27.02,
10,0.224,7.07,-992,36,75,-4.5,299,-28,-71,,-0.06,-27.61,32.71,27.61,
20,0.334,8.44,-1376,99,120,384.8,256,-29,-68,,-1.59,-28.15,30.55,28.19,

You can see the blank temperature cells, the small negative time just before launch, and that each data row finishes with a trailing comma, so a strict parser will see one empty field at the end of every data row.

Boards without the motion sensor use the same file in the same shape, just simpler. The motion columns, that is the three acceleration columns, the total acceleration, the three gyro columns and the pitch, roll, yaw and tilt, are all absent, and the header does not carry the motion statistics on its right hand side.

There is one addition rather than a removal: these boards include a Pressure(hPa) column, written to six decimals, straight after Altitude. So a Revision 3 or earlier log has just five columns, in this order: Time(ms), Altitude(m), Pressure(hPa), Velocity(m/s) and Board temp(C). Everything else on this page, the header groups, the time being measured from launch and the temperature being written about once a second, applies in the same way.