Explain these alternative representations in more detail

Author: PeterJCLaw

programming/sr/vision/index.md

@@ -239,12 +239,15 @@ roll
 
     This differs from `rot_x` in the zero point and direction to increase the value.
 
+Finally there are attributes which express the orientation in other forms:
 
 rotation_matrix
-:   The [rotation matrix](https://en.wikipedia.org/wiki/Rotation_matrix) represented by this orientation. A list of 3 lists, each with 3 items.
+:   The [rotation matrix](https://en.wikipedia.org/wiki/Rotation_matrix) represented by this orientation.
+    This 3×3 matrix is represented by a list of 3 lists, each with 3 values, in an arrangement compatible with tools such as `numpy`.
 
 quaternion
-:   The [Quarternion](https://kieranwynn.github.io/pyquaternion/#quaternion-features) instance represented by this orientation.
+:   The [quarternion](https://en.wikipedia.org/wiki/Quaternion) represented by this orientation.
+    On the physical kits this is implemented as a [`pyquaternion.Quaternion`](https://kieranwynn.github.io/pyquaternion/#quaternion-features) instance.
 
 <a id="Spherical"/>