74
S:Slope distance
α:Vertical angle from horizontal
K:Atmospheric refraction coefficient (0.14 or 0.2)
Re:Diameter of earth (6,370 km)
13.6 Distance range
Generally speaking,the maximum range which can be measured varies considerably
depending on the atmospheric conditions.For this reason,the specifications illustrate the
values for both good and normal weather conditions.
It is extremely difficult to judge when weather conditions are “Good”and when they are
“Normal”.With this instrument,the conditions noted below are used to differentiate
between the two situations,(good weather conditions for surveying are different from
normal weather conditions,and in surveying situations, cloudy skies are considered more
favorable than sunny skies.)
Weather conditions for measurement ranges are based on the following standard values:
Normal: Visibility of approximately 20 km,with slight shimmer and moderate wind.
Good: Visibility of approximately 40 km,overcast, with no shimmer and moderate wind.