Yaw in mobile app

Dear All, I am currently recording mobile sensors data using the matab app when placing the phone on the chest with staps in vertical position. The orientation (degrees) recorded is Azimuth, Pitch and Roll (XYZ). I was wondering how to obtain Yaw, as I am intending to measure trunk's lateral inclination when moving side to side.

Many thanks

Eduardo

Answer 1

[Les Beckham]

Typically, Azimuth is equivalent to Yaw (also Heading).

[Luis Eduardo Cofré Lizama]

Thansk for your answer Les. I just checked the diagram in Matlab and shows Azimuth as the angle between Y axis and North (from magnetometer) see below. May I be misinterpreting the diagram?

https://www.mathworks.com/matlabcentral/mlc-downloads/downloads/submissions/40876/versions/8/previews/sensorgroup/Examples/html/CapturingAzimuthRollPitchExample.html

[Les Beckham]

That diagram seems to confirm what I said about Azimuth being the same as Yaw (a.k.a. Heading).

Do you not agree?

[Luis Eduardo Cofré Lizama]

I see, I think I may have posed my question wrongly by assuming yaw = Z axis, what I need to obtain is the angles around the Z axis (when placing the phone in portrait), which are not? provided in the app. A quick test moving the phone around X and Y axes show that they are effectively pitch and roll and they come out in the sensor log file as Y and Z, respectively. However, I cannot get to understand the results coming out from X (Azimuth). The latter, to note, assuming that XYZ orientation are Azimuth, Pitch and Roll, respectively. I hope I am explaining my prob better now. Many thanks Les.

[Les Beckham]

You have actually managed to confuse me even more.

What do you mean "pitch and roll... come out in the sensor log file as Y and Z, respectively". According to the link you provided above Azimuth is the first column of the orientation data, Roll is the second column, and Pitch is the third column. No mention of X Y Z in the context of the output data.

[Luis Eduardo Cofré Lizama]

Hi again, below is the screenshot of the app, the second pic is the orientation table. Isn't X=Azimuth, Y=Pitch and Z=roll?

[Les Beckham]

Good question. The numbers in the app screenshot don't look even similar to the data table. Did you move the device?

I'm also curious about why the Orientation table is labeled XYZ (instead of Azimuth, Roll, Pitch).

I'd suggest capturing data from the app and the data download without moving the device to help find the correspondence between the axes.