kjorn wrote:I know a few riders who use a Woo and PIQ, both give the same readouts +/- half a meter. It must be so simple to test these devices, put a tape measure vertically, throw device up, take video. Does the device readout match the video? Repeat 500 times.
As kiteboarding is not a freefall sport compared to for example snowboarding, you always need to derive algorithm to detect launch and landing. Snowboarding is simple, read 0g from accelerometer and you are airborne. Kjorn, such event cannot be simulated like you suggest for kiteboarding. Optimizing behaviour like that only creates device capable of measuring freefall event, not a real kiteboard jump.
Here is a freefall video you 'suggested'. But remember, if without tossing device upwards you get same behaviour of accelerometer just by dropping. Only initial spike will be missing (because you did not accelerate the pendulum mass upwards first).
Kiteboarding device has much more complexity, I think I've explained this to you Kjorn earlier at least once.
- Orientate sensor mounted on board to earth coordinates for height in gravity field
- Remember if you do a megaloop you board is tossed aroung but rotations, kite pulling, swinging and even by your trick but still jump height is against gravity field
- Use accelerometer and gyroscope for orientation, additional magnetic sensors, but basically you 'reset' your gyros by accelerometer (when x, y and z is 1g stationary must be center of earth but on choppy waters you board is living causing acceleration sensor read-out changes)
- Keep calculating acceleration and speed vectors relative to gravity field
- Detect jump from above data
- While jump is going on, keep orientation relative to earth and update orientation & speed vectors
- When vertical speed = 0 you are at apex, what if you get secondary lift (like foilkites might give on fast zenith flying when redirecting)
- Estimate everything to point when you a) launch or b) land.
- Display figure of height to human hair level like Woo does (micro meter )
- Everything is analyzed on 100Hz to 1000Hz MEMS accelerometer and gyroscope with ADC noise (I don't know which sensor Woo uses and on what rate)
- Integrating acceleration over time to get speed and again to get position adds error
- How well you IMU and AHRS system is working together
If you watch this second video kite revolving behind the net and see monitor top-row (gyroscope and accelerometer) data you see that even by simply rotation there is a lot of movement and noise on the system.