# Physics / Engineering Help

Hello,

I need help translating the physics into something a programmer (and I ) can understand and implement. It helpful if you are familiar with accelerometers, particularly the iPhone’s . If you can program it yourself let me know.

There are two Physic Questions

I. Measuring and analyzing seismic tremors w/ accelerometer data

II. Measuring the degrees of deference in two vectors (this should be very easy)

I. Measuring and analyzing seismic tremors w/ accelerometer data

I’m building an iPhone application to measure seismic tremors similar to

But I want to combine the data for the 3 axis into a single data stream to measure total acceleration and frequency, not each axis separately.

So the physics help is:

1) combining the data from the 3 axis into a single number

2) Performing the Spectrum Analysis on the resulting data, to determine frequency(s)

3) Results do not need to be seen in real time. So if we need additional computational power we can have the results lag a couple sec.

Assumptions:

-10 seconds of data at sampling rate of 100 per sec_= 1000 data points for each axis for a total of 3,000 data points

- raw data will be ran through a High-Pass filter to remove gravity ‘noise’

1) combining the data from the 3 axis into a single number:Is it as simple as sqrt( x^2 + y^2 + z^2)

2) Performing the Spectrum Analysis on the resulting data, to determine frequency(s) and amplitude: Is a “fast Fourier transform” the answer? And how do we actually apply the formula to the numbers? [login to view URL]

3) Are there better ways of doing this ?

III. Measuring the degrees of deference in two vectors (this may be very easy).

How do know what direction in the plain of travel the movement took place? Would it be helpful to take some additional data points during the movement?

As an example

1st Vector 2nd Vector

x= 83 degrees 147

y= 32 89

z=59 32