NavList:

Marty Lyons:

Thank you very much for answering my questions regarding your recent Abney level measurements.

I was curious about how you defined ‘index error’ because an Abney level angular error can either be one of elevation or of depression. For the latter, with the index arm to the left of zero on the arc, I assume the correction would be an addition, and vice versa for an error in elevation.

My question about your machinist level sensitivity was borne of level-dependent solar elevation measurements I’ve done in the past (primarily by sun spots on a vertical surface), which led to measurements of sensitivity for the levels I was using. (Technically, spirit level sensitivity is the angular change in inclination that causes the bubble to move a specified distance.)

Chuck V