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12.4 Precautions When Performing Resection
In some cases it is impossible to calculate the coordinates of occupied point if the
unknown point and three or more known points are arranged on the edge of a single circle.
It is also impossible to calculate if the included angle between the known points is too
small. It is difficult to imagine that the longer the distance between the instrument
occupied and known points, the narrower the included angle between the known points.
Be careful for the points can easily be aligned on the edge of a single circle.
An arrangement such as shown below is desirable.
△▲：
unknown point
○●：
known point
It is sometimes impossible to perform a correct calculation such as shown below.
When they are on the edge of a
single circle, take one of the following methods:
(1) Move the instruction station as close
as possible to the center of the triangle.
(2) Measure one more known point which
is not on the circle.
(3) Perform a distance measurement on at
least one of the three points.
