The surveyor must constantly be alert to
the different conditions encountered in the field. Physical factors, such as
TERRAIN AND WEATHER CONDITIONS, affect each field survey in varying degrees.
Measurements using telescopes can be stopped by fog or mist. Swamps and flood
plains under high water can impede taping surveys. Sights over open water or
fields of flat, unbroken terrain create ambiguities in measurements using
microwave equipment. The lengths of light-wave distance in measurements are
reduced in bright sunlight. Generally, reconnaissance will predetermine the
conditions and alert the survey party to the best method to use and the rate of
progress to expect.
The STATE OF PERSONNEL TECHNICAL
READINESS is another factor affecting field-work. As you gain experience in
handling various surveying instruments, you can shorten survey time and avoid
errors that would require resurvey.
The PURPOSE AND TYPE OF SURVEY are
primary factors in determining the accuracy requirements. First-order
triangulation, which becomes the basis or "control" of future
surveys, is made to high-accuracy standards. At the other extreme, cuts and fills
for a highway survey carry accuracy standards of a much lower degree. In some
construction surveys, normally inaccessible distances must be computed. The
distance is computed by means of trigonometry, using the angles and the one
distance that can be measured. The measurements must be made to a high degree
of precision to maintain accuracy in the computed distance.
So, then, the purpose of the survey
determines the accuracy requirements. The required accuracy, in turn,
influences the selection of instruments and procedures. For instance,
comparatively rough procedures can be used in measuring for earthmoving, but
grade and alignment of a highway have to be much more precise, and they,
therefore, require more accurate measurements. Each increase in precision also
increases the time required to make the measurement, since greater care and
more observations will be taken. Each survey measurement will be in error to
the extent that no measurement is ever exact. The errors are classified as
systematic and accidental and are explained in the latter part of this text.
Besides errors, survey measurements are subject to mistakes or blunders. These
arise from misunderstanding of the problem, poor judgment, confusion on the
part of the surveyor, or simply from an oversight. By working out a systematic
procedure, the surveyor will often detect a mistake when some operation seems
out of place. The procedure will be an advantage in setting up the equipment,
in making observations, in recording field notes, and in making computations.
Survey speed is not the result of
hurrying; it is the result of saving time through the following factors:
The skill of the surveyor in handling
The intelligent planning and preparation
of the work
The process of making only those
measurements that are consistent with the accuracy requirements
Experience is of great value, but in the
final analysis, it is the exercise of a good, mature, and competent degree of
common sense that makes the difference between a good surveyor and an