Yaw Patch Test – Lines in Opposite Directions??

It is written in stone, somewhere in the ancient library of Multibeam Surveys, that Yaw Patch Test Lines MUST be in the same direction. The results are shown below:

Yaw Patch Lines and Results – The way we were all taught to do it

Ex 1: Yaw Patch Test Over Dam Sill – First Set of Lines are in the same Direction – Good Result

Example 2: Yaw Patch Test Over Dam Sill – 2nd Set of Lines are in the same Direction – Good Result

Recently while delivering training to experienced surveyors, one of the attendees said, “I was told recently that Yaw lines in opposite directions give good results. Is this true?” I immediately tested the statement, and it proved to be true.🤯

Example 2a: Before Starting the Yaw Test the known Yaw was reset to Zero – Yaw Lines are in Opposite Directions

Example 2b: Results of the Test: Yaw Test – Yaw Lines are in Opposite Directions but match the original result!

Why do the results not change?

The Geometry DOES NOT CHANGE!!!

Discussion Items:

Roll & Pitch results must be calculated and applied before running the Yaw Test – regardless of line running directions.
If you run two sets of Yaw lines to have two Yaw tests, you now have four!