Well, it IS pretty close to correct. An accelerometer measures exactly what
its name implies - acceleration. And 99% of the time the name implies
linear acceleration. So if you integrate that once, you have velocity. But
nowhere in this process do you get pitch, roll, azimuth, or any other
angular measurement. In order to get angular measurement, you need either a
pendulum, or some sort of gyro-stabilized platform.

In all cases with which I am familiar, the problem involves instruments
which are fairly expensive. The least expensive would be the sort of
instruments which are used to display attitude in aircraft. Start with the
needle and ball and all the implementations of artificial horizons that have
evolved over the years. The most accurate and stable over long term would
be some sort of inertial navigator. There may be newer, solid state gyros
which have evoved over the last few years, but I doubt that cost has
decreased significantly.

"Vic Fraenckel" wrote in message
...
"Gary Schafer" wrote
|For the pitch and roll, I don't think an accelerometer is not going to
| do it. It will give you rate of change. You could do some math and get
| degrees but it would not be accurate if the rate was different the
| next time you had a pitch or roll.
|

This is NOT correct. The ADXL is NOT measuring rate of change. It's output
measures the gravitational acceleration directly. I suggest that you read
AMD's data sheet on this product to understand how it works. I have used
the
ADXL to measure the inclination of a telescope tube with some success.

Regards,

Vic
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