Sokkia im-101 Operator's Manual page 63

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Precaution when performing resection
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• Instrument station may not be calculated when the included angles between the known points and the
station point are too narrow. Especially when the instrument station and the known points are far away,
it is difficult to know that the included angles between the known points are narrow.
When performing resection by angle measurement only and an unknown point (instrument station) and
three or more known points are arranged on the edge of a single circle, the coordinates of the unknown
point may not be calculated.
An arrangement such as that shown below is desirable.
It is sometimes impossible to perform a correct calculation in a case such as the one below.
When they are on the edge of a single circle, take one of the following measures.
(1) Move the instrument station as close as possible to the center of the triangle.
(2) Observe one more known point which is not on the circle
(3) Perform a distance measurement on at least one of the three points.
: Unknown point
(instrument station)
: Known point
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13. COORDINATE MEASUREMENT