In the compass calibration/setup is a dropdown with all kinds of Roll Pitch and Yaw options.
The default for an external mount compass is Roll180
What exactly does this do?
I’d like to better understand and know how I can know if I am using the proper setting.
Sorry probably a stupid obvious thing to you but I’m a bit lost.
I’m in the process of searching and reading around for a good description, not just waiting for an answer here.
In the “ideal” installation (“ideal”, in this case, meaning the compass is perfectly level in all three axis (yaw, pitch, and roll),and “magnetic” north points to “magnetic” north when it REALLY does) you don’t have to be concerned with any of those dropdown choices except the one marked “None”.
Unfortunately, we don’t always build things to the “ideal”. Or we don’t install them in “conventional” ways (maybe we install the compass sideways, or at an angle to the exact straight forward direction of the copter, etc.).
Some external compass units have been built with the compass itself having been installed upside down in the plastic housing that contains the entire unit. (Imagine having a coin which has a person’s face on one side and a dog on the other (lets say he is facing to the right when his “side” of the coin is facing up.) Now turn the coin over by lifting the right edge and rolling the coin over and laying it back down on a table. If you could see the dog now (you can’t - it is touching the table surface now), it’s head would be facing to the left (not to the right), The person’ hair is still in the same relative position as it was before, as is persons chest area. Only the dog’s front (and rear) end has changed relative positions to what it/they were when you started.
Now let’s take that same coin - only we’ll call the dog’s “head” end EAST and his rear “end” WEST. The top of the person’s head will be NORTH and the person’s chest area is SOUTH.
Performing the same procedure as above, we see that EAST and WEST actually exchange relative positions from when we started. If this were a compass instead of a coin, the compass reading would be 180 degrees off from what it should be.
If this is happening with your compass - i.e., your compass is showing a heading that is 180 degrees from what it should be, then you would use the Roll 180 selection from the drop-down list.
If your compass is showing it is “off” by only a few degrees, say less than 15, then you probably wouldn’t use any of the choices from the dropdown list to correct the error. Perhaps another compass calibration would help.