Samsung Photosphere orientations.txt data Samsung (and perhaps other vendors) photosphere source files include the photographs and 2 text data files.
sessions.meta - contents are self explanatory, labelled metadata info about the sphere.
orientations.txt - unlabelled columns.
Below are sample contents of orientations.txt:
-0.28355762 0.95895493 7.3134253E-4 -0.19058217 -0.057101488 0.9800091 0.9398263 0.2777497 0.19895127 2.8249815
-0.18003005 0.96288395 0.20110609 -0.044745624 -0.21225126 0.97619015 0.9826429 0.16674495 0.081296444 2.9338377
-0.27238333 0.95405024 0.12488161 0.17231762 -0.07932246 0.98184246 0.946633 0.28895682 -0.14279357 2.9741824
-0.43306527 0.8942725 -0.112832405 0.09304 0.16886118 0.9812387 0.89654785 0.41444248 -0.15633103 2.746174
-0.44042435 0.87723744 -0.19099967 -0.14356112 0.14119293 0.97951764 0.8862373 0.45882356 0.06375239 2.631776

My question is, does anyone know what these columns in orientations.txt represent?

1 row per image
10 columns of floats
no field names
I assume it may have to do with roll, pitch and yaw, but I'm not certain.
Perhaps accelerometry output?

Thank you very much in advance.
This is broadly related to these two other questions, but they don't really address my question.
Get the original photos after using PhotoSphere?
Is there any way to re-render a photosphere?
I've noticed that most elements are less than 1. Moreover the first 9 elements seem to be always less than 1. It looked like elements of a rotation matrix. So I grouped these elements into 3x3 matrix and it happened to be orthogonal, and it is in fact rotation matrix.
-0.28355762  0.95895493  7.3134253E-4
-0.19058217 -0.057101488 0.9800091
 0.9398263   0.2777497   0.19895127

If the phone is in landscape orientation and points to the North than the matrix is identity matrix:
 0.9999746    0.0067272037 0.0023434649
-0.0067065083 0.9999394   -0.008729676
-0.0024020493 0.008713738  0.9999592 

The last element in the row is the sum of all elements of the matrix. I don't know why it is added, because it doesn't seem to have any physical meaning, but I guess that it is some form of a checksum.