Civil Engineering Reference
In-Depth Information
a planimeter will not yield the accuracy of areas calculated using the mathematical
methods that computers have made possible.
There is case law which suggests that when a person purchases a parcel of land
and subsequently learns that the area actually conveyed is less than that called
for in the deed, the seller may be liable for damages and reimbursement for the
value of the shortage. If the seller uses “more or less” language he or she can
claim that the exact area was unknown and the buyer agreed to take whatever
actually existed. Such a claim may or may not prevail in court, and indeed, there
is case law to suggest that such a claim should not prevail. However, if the actual
area was unknown or uncertain at the time, it at least provides the seller with an
argument.
These issues have largely been eliminated by the use of computers. It is now
possible to calculate the area of an irregularly shaped parcel in surveying soft-
ware by merely clicking the mouse inside the parcel. If the software is also used
for drafting the final plan, it is not even necessary to write down the area as the
software will annotate the drawing with the calculated area. The area of a par-
cel remains an important element in its value so it is important for any surveyor
depending on a computer calculated area to still apply common sense and scru-
tinize the calculated area to determine if it is reasonable. When interpreting old
plans and deeds it is important to recognize that the stated area may not be repre-
sentative of the actual area.
4.5 Angles
An
Angle
is a measurement that describes the geometric relationship between two
intersecting lines. In boundary surveying in the United States, the
Sexigesimal
System
of angle measurement is used. The sexigesimal system is based on the
number 60. Angles are measured in
degrees
,
minutes
and
seconds
. There are 360°
(degrees) in a circle, 60′ (minutes) in a degree and 60″ (seconds) in a minute. As
can be seen from Fig.
4.5
, angles are always measured from a reference line and
can be measured to the right (clockwise) or to the left (counterclockwise).
Figure
4.6
shows a parcel of land described by angles and distances. Note that
the angles show the relationship of two lines that intersect. These intersections are
labeled A-D in the figure. Using the angles and distances, the parcel becomes a
rigid two dimensional geometric figure.
4.6 Bearings
Bearings
are angles measured from some standard reference direction, usually
true or magnetic north. The difference between angles and bearings is that angles
are measured from a reference line that can be in any direction but, in modern
