I fabricated a fixture to perform crane rail surveys but it doesn't seem to be as accurate as I had hoped. My process is to place the aluminum bar on the rail and rotate it until the dowel pins make contact with each side of the rail. Then use the bubble level on the prism to level it out before taking a shot with a 3 deg total station. The client is claiming that the numbers are off. I can't see what source of error I am missing unless the technician holding the fixture is just doing a sloppy job. On the most recent project, the rail was about 20 ft up, 40 ft span and 150 ft runway length. The station was set up about 2/3 the runway length. After the survey, the client straightened the runway with a piano wire and calibrated tape measure. I surveyed it again and it still didn't meet specifications. I'm starting to wonder if my process is flawed.

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