NOTE: Prism Constant/Offset refers to a value that compensates for the extra distance the
laser beam travels through the prism in order to reach the plumb line once it initially hits
the glass. It changes with differing construction and therefore changes with each prism
type. Using the wrong Prism Constant will lead to Systematic Errors in a survey.
NOTE: Vertical Height is always measured from the base of the pole to the centre line of
the prism. If unsure of the value, always take a manual measurement using a hand tape.
Before working on site it is important that all equipment has been set-up correctly and
you are aware of the sources of error that can be introduced at this time.
Correct Prism and Instrument settings
(1)
Ensure the ATP1 prism is clean and none of the
faces are damaged.
NOTE: The constant for the ATP1 prism is -7.0 mm
ATP1 360 prism
(2)
Make sure that you use a carbon robotic pole with 1.42 m
marking and that the black 26 mm spacer is always
attached.
(3)
Ensure the correct prism constant has been set in
MAGNET Field.
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