I'm not 100% familiar with this aspect of the G1, but I know Nintendo had a similar problem with their Wiimotes. That's why they have the sensor bar set up: they couldn't get their accelerometers to be accurate enough to track position.
On Jul 9, 2:23 pm, dilit <[email protected]> wrote: > Sounds like some signal processing/filter math is in > order.http://www.cs.unc.edu/~welch/kalman/ > > Anyone with experience? > D > > On Jul 9, 1:18 pm, dilit <[email protected]> wrote: > > > Just in case, > > > We did calibrate our phones. > > E.g. My phone's Gravity value is more like 8.7 vs 9.81. > > While static, the phone's accel values were acceptable. > > As soon as the phone was in motion, the acceleration (position) > > data went out to lunch. > > > FYI, marketing = lying 99% of the time. IMO > > > On Jul 9, 1:05 pm, dilit <[email protected]> wrote: > > > > We are writing an application that uses acceleration sensor data to > > > plot phone's movement in 3D. > > > We are finding gross inconsistencies in the actual data output by the > > > sensor. Also, sampling rates > > > vary greatly from 8 to 200 millis. (using System.currentTimeMillis()) > > > > Specifically, when we try to draw a circle with G1 flat on the table > > > all the time (filtering out gravity accel 9.8), > > > most of the time we would get a plot of phone's position that is not a > > > circle at all. Lots of times, it would be close to a straight line. > > > Sometimes, it would start drawing an arc, but would not close the > > > circle shooting off in a random direction. > > > > We tried to eliminate the time variable, by substituting a constant > > > time sampling rate (10 millis) to calculate phones position, but the > > > result was > > > very close to what we had before (shapewise). Also, the acceleration > > > in Z direction when the phone is displaced lying flat on a table (XY > > > plane) varies too > > > by +/- 2 units which is a lot. > > > > I do not think it is an error in our code, as we have checked it many > > > times. If there were an error indeed and the > > > accelerometer worked properly, we would see a consistently wrong > > > depiction of the phone's movement. Unfortunately, repeating the same > > > movement > > > (circle) would produce sometimes wildly differently shaped plots. > > > > It all comes down to us wanting to know if that is indeed the case > > > that the G1 accelerometer is very unreliable and inconsistent device > > > when used for more or less precise > > > measurements? Is there some documentation/facts paper that would tell > > > us just how reliable accelerometer is? > > > > Thanks for you help! > > > Dmitriy --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/android-developers?hl=en -~----------~----~----~----~------~----~------~--~---
