There can be a few different causes for movement of a ShapeArray (SAA) in an unexpected direction:

1. The azimuth offset of the X-mark on a vertical ShapeArray was not set correctly

There might have been an error in the azimuth offset value that was assigned for the X-mark of the ShapeArray, or perhaps no value was assigned at all and the X-mark is not aligned with any known direction. If the shape of the hole has some known non-verticality in a particular direction, this shape (and the azimuth of the ShapeArray) can be verified using the ‘View | Absolute Shape’ menu item of SAAView when looking at either unfiltered or filtered data. If the azimuth offset of the ShapeArray is correct, then the deviation of the hole in the X and Y directions should match the known shape of the hole.

If the azimuth offset of the ShapeArray is not correct, there will in general be some re-distribution of the X and Y components of the absolute shape. Various additional azimuth angles (aza angles) could be tested in SAAView to see if a better match with the known shape can be achieved. Note that if an aza angle is used for a ShapeArray, and you are looking at unfiltered data, you will need to make sure that the ‘Apply Aza’ checkbox on the main window of SAAView is checked prior to pressing the ‘ViewUnFiltered’ button.

2. Rotation of the ShapeArray has occurred

Rotation of an inclined or near-vertical ShapeArray will tend to result in an apparent deformation that is orthogonal to the direction of incline. For a discussion of rotation effects in SAA and how to eliminate rotation or correct for it, please see: 'Effects of Rotation of a Non-Horizontal ShapeArray Within its Conduit'.

3. The reference end of the ShapeArray is not in stable soil

If the reference end of the ShapeArray is actually moving, then the deformation measurements made along the ShapeArray cannot be linked to any fixed Cartesian coordinate system, unless the movement at the reference end is somehow known (for example with the use of GPS technology).

4. Check to make sure that no segments have become damaged

If a segment has become damaged so that its accelerometer outputs are no longer valid, it will tend to result in a significant apparent deformation. See 'How do I check data collected using a data logger to make sure it is good?' for details on checking the total accelerations of a ShapeArray connected to a logger or 'Total Acceleration Check' section of 'SAARecorder' for checking total accelerations of a ShapeArray in SAARecorder.