Exactly but that’s a LOT of data – already at 1Hz the csv files easily reach 5Mb.
This software was pretty useful when I was doing my flight testing. https://www.cloudahoy.com/
My initial thought is that it might be more accurate to use an accelerometer/gyroscope (to feel for rotation and detect an upwards acceleration) or microphone (to listen for rumbling wheels) than GPS to detect when the wheels have left the ground, but that GPS will probably give a good value for the 50ft obstacle clearance. With accurate timings, one should be able to interpolate the GPS ground track well enough to get an accurate take-off distance.
If I wanted an accurate value for my own aircraft I would probably rig a £10 cycle computer sensor to one of the main wheels, and use it to make ‘clicks’ to the microphone input of a phone or ipad. Usually brakes are set very lightly ‘on’ to stop wheels spinning in the air, so they should slow noticeably at the point of take-off. Rules and regulations may apply.
I found that using a CSV file from ForeFlight and Google Earth (?) one could interpolate between points pretty easily to determine the ground roll. I haven’t done it in a few years but it served my purpose at the time.
The time & distance it takes to accelerate to a given ground or indicated speed (combined with wind & weather/runway data) are way more relevant than distance to liftoff
One can liftoff at early speeds aircraft will be stuck in ground effect if acceleration is not enough, same one can delay liftoff speed…
If we know our barrier speed, typically Vx, we can work out the distance to the later of achieving barrier speed, or achieving barrier height. Alternatively if you have a typical lift off speed, which avoids you from not accelerating out of ground effect you could also calculate the distance of the ground run to lift off.
Assume Puddle-jumper Sport takes ten seconds to accelerate to 60 mph IAS (we assume the IAS is close to CAS). To work out acceleration v is final velocity, u is initial velocity (ie zero) and acceleration is a. Formula would be v= u + at. v is approximately 27 m/s. Solving for a we get 2.7 m/s2
Now how far did we travel in reaching v. The formula would be ut + 1/2at2. In this case 0 + 1/2 × 2.7 × 10 squared resulting in around 135m.
Now presumably this is all based on a level, dry tarmac runway at SL with no wind etc
You would then need to apply rough safety factors, for example as in:
