## ASK AN EDUCATOR! – How can I measure the height of my model rocket?

What would be a good way to gauge the height of my model rocket?

Well, there are really quite a few ways to make the measurement. In a perfect world, your rocket launches perpendicular to the earth’s surface, and you can use a trigonometry to calculate the altitude based on your distance from the launch pad and the apparent angle from you to the rocket. You can use a tool, such as an inclinometer or “altitude tracker,” which uses your line of site to the rocket and references it to a string held vertically due to gravity. You then record your angle when the rocket hits apogee and through trig or the supplied calculator, you can determine the height. The problem with this method is that it doesn’t take into account any drift, which changes the your distance to the rocket and skews the measurement.

Alternatively you can use the same method, but with two observers. NASA has a nice description and calculator that does the trig for you and gives you a much more accurate measurement.

Another method it to buy a altimeter like a PerfectFlite APRA Altimeter. This device uses a barometer and returns a beep corresponding to the altitude an achieved velocity. You can also find more sophisticated devices that have computer interfaces, GPS, temperature, etc.

I hope this answers your question, and have fun with you calculations!

Don’t forget, everyone is invited to ask a question!

“Ask an Educator” questions are answered by Adam Kemp, a high school teacher who has been teaching courses in Energy Systems, Systems Engineering, Robotics and Prototyping since 2005.

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Filed under: educators — by akemp, posted July 15, 2012 at 11:51 am

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## 1 Comment

1. Actually, the barometic pressure should give you a better height information than GPS. The drift on the vertial is +/- 75ft for GPS, while for barometric, it would be +/- 25 ft.

Comment by Zak Zebrowski — July 15, 2012 @ 1:52 pm