Get Azimuth & Elevation from iPhone Accelerometer Data

In summary: For example, imagine they are casting a fishing net. In this case, they would be trying to estimate the position of the net at any given time. In summary, Robert is trying to reconstruct a 3D path from accelerometer data from someone throwing a ball. He is making assumptions about the movement and is trying to model a baseball toss. He wonders if there is a better example for the students.
  • #1
rd42
6
0
I'm almost to timid to ask, I haven't had a math class in over 10 years and even longer for physics. My apologies if I dumb down the forum a little bit.

I'm grabbing accelerometer data out of the iPhone of someone doing a throwing motion. I'm not really sure if it is possible to get the azimuth and elevation from the accelerometer data, and if it is, whether I have the computational skills to work the formulas in a reasonable amount of time.

Are there any generic excel spreadsheets or formulas for plotting information about what the iPhone might be doing in 3D space from just the accelerometer measurements?

Thanks you for any help or hints.

Robert
 
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  • #2
rd42 said:
I'm grabbing accelerometer data out of the iPhone of someone doing a throwing motion. I'm not really sure if it is possible to get the azimuth and elevation from the accelerometer data,
You only get one vector (linear net inertial force) from the accelerometer, no angular acceleration, right? In that case you cannot reconstruct the 3D path, if the iPhone is rotating in space.
 
  • #3
I'm not sure. You get acceleration in x,y and z over time.
 
  • #4
rd42 said:
I'm not sure. You get acceleration in x,y and z over time.

This is the acceleration in the device's local space. If you don't know how the device is oriented in global space, you cannot compute the path in global space in a general way. But depending on the expected movement and what you want to get out of this, you can make some assumptions.
 
  • #5
Excellent, I like assumptions :) and compounding error is cool too.

I will definitely be making assumptions. I'm trying to model a baseball toss for some young kids studying physics. I'm not sure what other assumptions I will need, but I will assume a starting accel of zero, I will start recording when the accelerometer senses a substantial acceleration increase (the start of the throw) and stop recording when there is a substantial decrease in acceleration. The students will be instructed not to follow through on the throw and not to let go of the iPhone.
 
  • #6
Like AT said, you can't get an accurate 3D trajectory unless you also have 3 gyros in the phone in additional to 3 accelerometers. Even if you have all these, it would be a big challenge to make them work. iPhone can't be turn into an inertial navigation system yet.
 
  • #7
Oh well, thanks for your help.


I wonder what a better example might be for the students.
 

1. How accurate is the azimuth and elevation data obtained from iPhone accelerometer?

The accuracy of the azimuth and elevation data depends on several factors, such as the quality of the iPhone's accelerometer, the calibration of the device, and the precision of the measurement algorithms. In general, the data can be accurate within a few degrees, but it may vary in different conditions and environments.

2. Can the iPhone accelerometer be used to determine the azimuth and elevation of any point on Earth?

No, the iPhone accelerometer can only measure the device's orientation relative to the Earth's magnetic field and gravity. It cannot determine the exact position of a point on Earth without additional information, such as GPS coordinates.

3. How does the iPhone accelerometer calculate the azimuth and elevation data?

The iPhone accelerometer measures the acceleration of the device along three axes (x, y, and z) using tiny sensors. The data is then processed using complex algorithms that take into account the Earth's magnetic field and gravity to calculate the device's orientation in 3D space, which can be translated into azimuth and elevation values.

4. Can the azimuth and elevation data obtained from the iPhone accelerometer be used for navigation purposes?

The azimuth and elevation data from the iPhone accelerometer can provide a general sense of direction and orientation, but it is not precise enough for navigation purposes. For accurate navigation, it is recommended to use a dedicated GPS device or app.

5. Are there any potential applications for using the iPhone accelerometer to get azimuth and elevation data?

Yes, there are several potential applications for using the iPhone accelerometer to get azimuth and elevation data, such as augmented reality apps, geocaching, and basic navigation. It can also be used in scientific research and education for understanding the Earth's magnetic field and gravity.

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