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7.8
System Accuracy
60
General Technical Data of the Product
Several factors can influence the system's accuracy for determining the loca-
tion 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.
Angular accuracy
9²
*
Orthogonal to the line of sight.
Refer to the data sheet of the respective instrument model for
☞
information about the angular accuracy.
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"
Because of the maximum measurement distance for iCT30, only the
☞
fixed value is specified. Refer to "7.2 Distance Measurement with
Reflectors".
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 dis-
tance-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 auto-
mated 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:
Prism type
Leica GPR1
Leica GPH1P
Possible deviation
~3.0 mm
Circular prism
Precision circular prism
*
at 60 m distance
Centring accuracy
1.0 mm
0.3 mm
Technical Data
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