FL/FR Observations & Error

Here in NJ, we are required to have our guns calibrated yearly and retain the certificate of calibration. Turning double faced angles, of course, is best practices but will not eliminate distance errors. It's always good to culminate your guns regularly as well.

Better that any instrument error is small

Makes it much easier to turn to an azimuth if you dont have to remember to continually add/delete half your error

Yes, D+R eliminates most errors BUT it does NOT eliminate the error due to the inclination of the standing axis. However, the magnitude of this error depends on the vertical angle, and is zero for horizontal sights, and most sights are close enough to horizontal that the effect is minimal. It can be significant if sighting to the sun or polaris, etc at a steep angle. Modern total stations with dual axis compensators eliminate this error unless there is a problem with the compensator. Older instruments without compensators are affected on steep sights.

If nothing else there is still the single face topography shots to be considered. If the gun is not well collimated, those are going to be sloppy. All the more so as the shots get longer.

I preach that to my crews regularly.

I've struggled with this since I was first handed a robot.

I was taught in the age of booking double angles.

When I received my first Yellow robot, paired with (the thankfully now relegated to history) LM80, you couldn't take measurement in F2 (except for in "survey basic", which I manually booked for all my control work).

I knew, form the literature accompanying the software, that a collimation correction was being applied to F1 observations but I couldn't find any information on what this meant if you physically did double the angle. Was the correction being applied in both faces? Was it being applied unevenly only in one?

My first post on this page, almost twelve years to the day, was a question about this. A dozen years on and I still don't know the answer.

Collimation correction and DIN 18723 - Strictly Surveying - RPLS.com