Comments on: iPhone rocket data quicklook http://www.lolife.com/2008/11/iphone-rocket-data-quicklook/ blunt observations Fri, 07 Oct 2011 01:20:24 +0000 hourly 1 http://wordpress.org/?v=3.2.1 By: lolife http://www.lolife.com/2008/11/iphone-rocket-data-quicklook/comment-page-1/#comment-1299 lolife Wed, 05 Nov 2008 03:37:54 +0000 http://www.lolife.com/blog/?p=786#comment-1299 Yeah, either the motor didn't go to full thrust or the altitude has huge error bars. In the latter case, I'd think that there would be more scatter in the data, but maybe the GPS altitude calculation has a low-pass filter on it or something. I expected the altitude data to suck way more than it looks like it does. Yeah, either the motor didn’t go to full thrust or the altitude has huge error bars. In the latter case, I’d think that there would be more scatter in the data, but maybe the GPS altitude calculation has a low-pass filter on it or something. I expected the altitude data to suck way more than it looks like it does.

]]> By: nasty http://www.lolife.com/2008/11/iphone-rocket-data-quicklook/comment-page-1/#comment-1298 nasty Tue, 04 Nov 2008 15:03:32 +0000 http://www.lolife.com/blog/?p=786#comment-1298 You're right, your altitude and thrust numbers don't quite make sense. Do you have a way to calibrate the elevation data you're getting? You’re right, your altitude and thrust numbers don’t quite make sense. Do you have a way to calibrate the elevation data you’re getting?

]]> By: mholger http://www.lolife.com/2008/11/iphone-rocket-data-quicklook/comment-page-1/#comment-1296 mholger Tue, 04 Nov 2008 12:18:10 +0000 http://www.lolife.com/blog/?p=786#comment-1296 Unless your GPS has a calibrated barometric altimeter, then your altitude readings will be off, potentially by tens of meters. Based on the 3DGPS readings I've gotten on circuit hikes, I've had the altitude of my (parked) car change up to 100m from when I've left it to when I got back. Surely it's not enough to explain your data entirely, but it's something to factor in. Also, in terms of error bars, you should be able to get the (horizontal) relative accuracy from the GPS, and you can roughly calculate your vertical error from that... Some good reading: http://gpsinformation.net/main/altitude.htm Unless your GPS has a calibrated barometric altimeter, then your altitude readings will be off, potentially by tens of meters. Based on the 3DGPS readings I’ve gotten on circuit hikes, I’ve had the altitude of my (parked) car change up to 100m from when I’ve left it to when I got back.

Surely it’s not enough to explain your data entirely, but it’s something to factor in. Also, in terms of error bars, you should be able to get the (horizontal) relative accuracy from the GPS, and you can roughly calculate your vertical error from that…

Some good reading: http://gpsinformation.net/main/altitude.htm

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