# Kicking a Football and Taking Measurements Project

Hello,

I am working on a project to measure (approximate) the distance traveled by a football kicked into a training net. The idea that someone kicks a football (foam football stuffed with a bunch of sensors) into a training net and based on the data collected in the first couple of seconds (before the football hits the net), I can approximate footballs path in real life (while making assumptions about wind, etc). This is just for a game application, not for scientific measurements.

I tried doing this using an IMU (https://www.sparkfun.com/products/11028), but turns out that because of this (http://stackoverflow.com/a/6648538/154611) it's completely inaccurate and useless.

Could I take other measurements to make this work? Could I use an ultrasonic distance measurement for this? Would really appreciate any help or tips!

Thanks, Greg

Why doesn't the IMU work? That sounds like the perfect solution for this. You basically want to measure the force on the football along the 3 axis to tell where it would go, correct? Acceleration is just F/M, so an acceleration measurement should tell you trajectory. Admittedly if the football spins, that won't help, but I imagine with some modelling, you could figure it out, espeically since you have gravity as a reference.

Thanks for your reply. I think that's a good point of getting the force. If the acceleration is based on the coordinates, do I measure change in acceleration and thus change in force?

When the football is in free flight, neglecting air resistance, an accelerometer will read zero g. You can't use them to get trajectory information during flight, but you can estimate the flight path if you can accurately measure the initial forces that set the football into motion.

jremington: When the football is in free flight, neglecting air resistance, an accelerometer will read zero g. You can't use them to get trajectory information during flight, but you can estimate the flight path if you can accurately measure the initial forces that set the football into motion.

This, the only difficultly is in measuring the initial accelerations fast enough. However, you might just need to measure the max in all 3 directions to get a valid response. However, once you do that, you should be able (with many assumptions) figure out where the ball would go. The gyros would also tell you about any rotation put on the ball.

Thanks for your replies! Yeah this is just for a game-like simulation. And only need to measure for a short amount of time and model the rest. I will see if I can get better info out of the IMU.

What is your budget? I ask because real time kinematics (RTK) GPS would give you adequate resolution to give you the x and y coordinates of the ball, consider z altitude. The budget would be about \$300 for the RTK solution, probably more than what you are interested in but thought I would mention it. For altitude I would use a precise MEMS barometer.

Another newbie resurrecting a necrothread... this one is well over five years old, and the OP is not even a member here any more.