System Accuracy: Several factors can influence the system's accuracy for determining the location of a prism
• Internal ATR accuracy
• Angular accuracy of the instrument
• Type and centring accuracy of the prism
• Selected EDM measuring program
• External measuring conditions
Therefore, the overall pointing accuracy of the determined point location can be lower than the given angular accuracy and the ATR accuracy. The following paragraphs provide a short overview of these influencing factors and their possible intensities.
Angular accuracy
The accuracy of angular measurements depends on the instrument type. The angular accuracy for total stations is typically in the range from 0.5² to 5². The resulting error depends on the measurement distance. 
EDM accuracy
The distance measurement accuracy usually consists of two parts: a fixed
value and a distance-dependent value (ppm-value).
Example: "Single measurements: 1 mm + 1.5 ppm"
ATR accuracy
Automatic target aiming accuracies, like those of the ATR, are in general the
same as the stated angular accuracy. Therefore these accuracies are also distance-dependent parameters.
External impacts, like heat shimmer, rain (prism surface covered by rain drops),
fog, dust, strong background lights, dirty targets, alignment of the targets etc.
can have a significant influence on the automated target. In addition the
selected EDM mode affects the ATR performance. Under good environmental
conditions and with a clean, properly aligned target the accuracy of the automated target aiming is equivalent to the manual target aiming (presumed valid calibration values).
Type and centring accuracy of the prism
The prism centring accuracy depends mainly on the used prism type, for example:
Additional influencing factors
When determining absolute coordinates, the following parameters can also
affect the resulting accuracy:
• Environmental conditions: temperature, air pressure and humidity
• Typical instrument errors, such as horizontal collimation error or index error.
• Proper functioning of laser plummet or optical plummet
• Correct horizontal levelling
• Setup of the target
• Quality of additional equipment, such as tribrach or tripod.
Telescope
Compensator
Level
Four button keyboard unit
Instrument ports
Pin Assignments of the 5 Pin LEMO-0 Port
Instrument Dimensions
With CCD6
Weight
Laser plummet
Drives
Motorisation
Power
Internal battery
External battery
Environmental specifications
Reflectors
Electronic Guide Light (EGL)
Automatic corrections: The following automatic corrections are made
• Line of sight error
• Tilting axis error
• Earth curvature
• Circle eccentricity
• Compensator index error
• Vertical index error
• Standing axis tilt
• Refraction
• ATR zero point error