Civil Engineering Reference
In-Depth Information
Fig. 4.15
Example of an error of closure
of the property being described. For example, in Fig.
4.15
each of the four bound-
ary lines could contain small errors. Sometimes these errors will accumulate and
sometimes the errors will tend to cancel each other. The resultant error of closure
represents the sum (actually the vector sum) of the all of the errors. Large errors
of closure may be indicative of sloppy measurement techniques, a poorly calibrated
instrument or tape or a blunder. If measurements are recorded manually, a large
error of closure may result from improperly recording readings or measurements.
Sometimes, the error of closure may provide a clue as to where the error
may have occurred, particularly if the error is large. For example, in Fig.
4.15
, if
the bearing of the error of closure were N54°E, there is a good chance that the
length of line which has a bearing of S54° 06′ 02″W was measured incorrectly.
Alternatively, either or both of the angles at points A or B may have errors.
In the chapter on calculations we will see that the concept of closure also
applies to traverses. (Traverses are the actual lines which the surveyor measures.
Traverse lines are usually not the same as property lines. This will be described in
detail later on.)
