Get Azimuth & Elevation from iPhone Accelerometer Data

  • Context: Undergrad 
  • Thread starter Thread starter rd42
  • Start date Start date
  • Tags Tags
    Accelerometer Iphone
Click For Summary

Discussion Overview

The discussion revolves around the feasibility of deriving azimuth and elevation angles from accelerometer data collected from an iPhone during a throwing motion. Participants explore the limitations of using accelerometer data alone for reconstructing 3D motion and consider assumptions that might be necessary for modeling purposes.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant expresses uncertainty about whether azimuth and elevation can be derived from accelerometer data, highlighting a lack of computational skills.
  • Another participant points out that the accelerometer provides a single vector representing linear net inertial force, which may not be sufficient for reconstructing a 3D path if the device is rotating.
  • A different participant notes that while acceleration data is available in three dimensions, the orientation of the device in global space is crucial for accurate path computation.
  • One participant mentions the intention to make assumptions about the motion, such as starting acceleration being zero and recording during specific phases of the throw.
  • Another participant emphasizes that accurate 3D trajectory reconstruction requires additional sensors, such as gyroscopes, and acknowledges the challenges involved in using the iPhone as an inertial navigation system.

Areas of Agreement / Disagreement

Participants generally agree that deriving accurate 3D trajectories from accelerometer data alone is problematic and that additional sensors would be necessary. However, there is no consensus on the specific assumptions that should be made for modeling the throwing motion.

Contextual Notes

Limitations include the dependence on the device's orientation in global space and the challenges associated with using accelerometer data for accurate motion tracking. The discussion also reflects uncertainty regarding the computational methods available for processing the data.

Who May Find This Useful

This discussion may be useful for individuals interested in motion tracking, sensor data analysis, and educational modeling in physics, particularly in the context of using mobile devices for data collection.

rd42
Messages
6
Reaction score
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
 
Physics news on Phys.org
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.
 
I'm not sure. You get acceleration in x,y and z over time.
 
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.
 
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.
 
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.
 
Oh well, thanks for your help.


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

Similar threads

Undergrad How to get up/gravity-vector from 3-axis accelerometer data?
  • · Replies 1 ·
Replies
1
Views
7K
Undergrad Calculating Pitch and Roll Relative to a Velocity Vector from IMU Data
  • · Replies 5 ·
Replies
5
Views
4K
Undergrad Velocity issues -- experimental data from an accelerometer and a gyroscope
  • · Replies 8 ·
Replies
8
Views
2K
Undergrad How Do You Calculate Vertical Displacement from Experimental Data with Noise?
  • · Replies 11 ·
Replies
11
Views
4K
Using iPhone accelerometer data
  • · Replies 25 ·
Replies
25
Views
60K
How to calculate Distance from Accelerometer Data
  • · Replies 9 ·
Replies
9
Views
10K
Data analysis by guessing, checking and fixing
  • · Replies 5 ·
Replies
5
Views
4K
Tri Axis Accelerometer Data Help
  • · Replies 4 ·
Replies
4
Views
6K
Graduate Help Understanding Black Hole Theories
  • · Replies 2 ·
Replies
2
Views
2K
Undergrad Where is my calculation of sun angle incorrect?
  • · Replies 15 ·
Replies
15
Views
5K