SURVEYING: PRINCIPLE OF ECONOMY AND ACCURACY

Surveys are only ever undertaken for a specific purpose and so should be as accurate as they need to be, but
not more accurate. In spite of modern equipment, automated systems, and statistical data processing the
business of survey is still a manpower intensive one and needs to be kept to an economic minimum. Once
the requirement for a survey or some setting out exists, then part of the specification for the work must
include a statement of the relative and absolute accuracies to be achieved. From this, a specification for
the control survey may be derived and once this specification has been achieved, there is no requirement
for further work.
Whereas control involves working from ‘the whole to the part’ the specification for all survey products
is achieved by working from ‘the part to the whole’. The specification for the control may be derived from
estimation based upon experience using knowledge of survey methods to be applied, the instruments to
be used and the capabilities of the personnel involved. Such a specification defines the expected quality of
the output by defining the quality of the work that goes into the survey. Alternatively a statistical analysis
of the proposed control network may be used and this is the preferable approach. In practice a good
specification will involve a combination of both methods, statistics tempered by experience.