Spectra Precision Focus 30, User Manual

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6 Instrument Technology
78 Spectra Precision FOCUS 30 User Guide
Distance Measuring Technology
Spectra Precision FOCUS 30 Total Stations are equipped with a combined distance
unit. This means that the instrument can measure to a prism or to normal surfaces
(reflectorless mode).
The laser distance unit is based on the phase comparison method. The distance unit is
coaxial with the line of sight and transmits an intensity modulated optical measuring
beam that is reflected by a prism or scattered by a natural surface on which the beam
is directed. The phase difference between the transmitted light and the reflected
received light is detected and represents the distance.
In prism mode, the unit operates as a fast and precise long-range distance meter. In
reflectorless mode, the unit transmits a collimated visible red laser beam to the target
point and then calculates the distance between the transmitted and the received light.
The distance unit software will detect erroneous single distance measurements such
as those caused by an obstruction passing through the measurement beam, and will
ignore such readings in the computation of the final distance.
Unambiguous range for distance measurement:
• Prism mode - 7350m
• Reflectorless mode - 1100m
Note –
Do not measure to a prism in reflectorless mode. Distances up to 1100 m are
not allowed because a Class 3 Laser is used for reflectorless distance measurement.
For distances longer than 1100m, the instrument's distance accuracy is not
guaranteed.
Beam Divergence
All distance meter measurement beams diverge as the range from the instrument
increases. The divergence of the distance meter beam relates to an increase in the size