iPhone dead reckoning - i reckon not
by Orion Elenzil · in iTorque 2D · 10/27/2009 (7:10 pm) · 4 replies
i spent some time this weekend programming with the iPhone's accelerometers (not using T2D, just the basic objective-C stuff) in the hopes that the device would prove capable of dead-reckoning over small movements.
ie, put it down on the table, press "tare", then slide it around on the table, and it's able to detect when it's back where it started. basically i found that the device seems nowhere near accurate enough for this sort of application. is that pretty much common knowledge ?
i'm using just simple euler integration:
vel += acc * dt
pos += vel * dt
and not doing any low-pass filtering or stuff like that.
am i right and this is a red-herring, or should i keep trying ?
i'm only concerned w/ 3-DOF linear motion, not rotation.
ie, put it down on the table, press "tare", then slide it around on the table, and it's able to detect when it's back where it started. basically i found that the device seems nowhere near accurate enough for this sort of application. is that pretty much common knowledge ?
i'm using just simple euler integration:
vel += acc * dt
pos += vel * dt
and not doing any low-pass filtering or stuff like that.
am i right and this is a red-herring, or should i keep trying ?
i'm only concerned w/ 3-DOF linear motion, not rotation.
About the author
Recent Threads
#2
i'm seeing a noise floor of about 0.012 or 0.013 on each tick, which is at 60 or 100 Hz. apple nicely calibrated this value so that one gravity = 1.0. so the noise seems to be 1/100th of one gravity. i'm using just the straight UIAccelerometer stuff.
10/27/2009 (11:16 pm)
really ?i'm seeing a noise floor of about 0.012 or 0.013 on each tick, which is at 60 or 100 Hz. apple nicely calibrated this value so that one gravity = 1.0. so the noise seems to be 1/100th of one gravity. i'm using just the straight UIAccelerometer stuff.
#3
www.inition.co.uk/inition/product.php?SubCatID_=17&URL_=product_mocaptrack_i...
10/29/2009 (11:06 pm)
Accurate accelerometers are a little more expensive... about 100 times more expensive in fact ;-)www.inition.co.uk/inition/product.php?SubCatID_=17&URL_=product_mocaptrack_i...
Torque Owner Eyal Erez
From the little bit that I've played with accelerometer I found that it seems like there is already some sort of low-pass filtering. it really detects nothing when the numbers are close to 0.
Too bad. I wish they would leave the filtering to us.