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One can perform additions, subtractions and conversions in the sexagesimal
system as follows:
0 0
+ 35 17’46’’ - 90 00’00’’
0 0
25 47’36 35 17’46’’

0 0 0
60 64’82’’ = 61 05’22’’ 54 42’14’’

0
Conversion 35 30’ = 35.50

0
0
142.125 = 142 07’30’’

3.3 Mistakes and Errors
No measurement can be perfect or exact because of the physical limitations of
the measuring instrument as well as limits in human perception. The difference
between a measured distance or angle and its true value may be due to mistakes
and /or errors. These are two distinct terms. It is necessary to eliminate all mistakes
and to minimize all errors when conducting a survey of any type.

BLUNDERS: A blunder is a significant mistake caused by human errors. It
may also be called a gross error. Generally, it is due to the inattention or
carelessness of the surveyor and it usually results in a large difference between the
observed or recorded quantity and the actual or the true value.
Mistakes may be caused by sighting on a wrong target with the transit when
measuring an angle, a by tapping to an incorrect station. They also may be caused
by omitting a vital piece of information, such as the fact that a certain measurement
was made on a steep slope instead of horizontally.

The possibilities for mistakes are almost endless. However, they are only
caused by occasional lapses of attention.

ERRORS: An error is the difference between a measured quantity and its true
value, caused by imperfection in the measuring instrument, by the method of
measurement, by natural factors such as temperature, or by random variation in
human observation. It is not a mistake due to carelessness. Errors can never be
completely eliminated, but they can be minimized by using certain instruments and
field procedures and by applying computed correction factors.

3.3.1 Types of errors
There are two types of errors: Systematic errors and Accidental errors.

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