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You [your
name] doe swear by the great name of ye
living God that you shall faithfully attend to and
discharge your office of Surveyor unto which you
are appointed without favour or respect to
persons. You _______. and
_______, Being desired to assist [name of
surveyor]. -- Surveyor; in carying the Chain,
Do Swear by the Everliving God that you will
faithfully assist the said Surveyor in his servis
and that you will keep a true account of all Lines
on measures by you taken and the same give up to
said Surveyor at his desire according to your best
Skill and ability. So help you God. Backstaff A wooden device that allows
the user to take an angle between two distant
objects. Compasss A general term used to denote
any magnetic device that determines
angles. A very large compass. Usually
six to eight inches in diameter and has fixed
vertical sighting blades. Again, a large compass, but
with a low power telescope that can be adjusted
both horizontally and vertically instead of the
sighting blades. Mile 8 furlongs :: 80 Chains ::
8000 links :: 5280 feet Furlong 10 chains :: 800 links :: 660
feet 100 links :: 100
feet Gunter's Chain 4 rods :: 66 feet :: 100
links Rod (Perch, Pole) 16.5 feet :: 25
links 1.0 foot :: 12.00
inches Gunter's Link 0.66 feet :: 7.92
inches Township 36 sections :: 138,240
acres Section 6 square miles :: 3,840
acres Square Mile 640 acres Quarter Section 160 acres :: (1
farm) Acre 160 Square Rods :: 10 square
chains :: 43,560 square feet Rood 0.25 acre :: 40 square rods
:: 10,890 square feet Square Rod 272.25 square feet Square Yard 9 square feet The Surveyor's
compass differs from the ordinary magnetic compass
in that the East to West direction is reversed.
This is because the reading is always taken from
the back of the needle. Furthermore nearly all of
these compasses are also numbered from zero (North)
to 180 degrees rather than from zero to
360°. The Theotolyte
is a much newer and more sophisticated device
than its older cousin, the
circumferentor. The first
improvement is the introduction of a telescope
with cross hair sighting. The second addition is
the use of a vernier scale (see below) that
increases the accuracy of measurement. And
finally, the introduction of a ring dial with
vernier scale that allows vertical angles to be
taken at the same time as the traditional
horizontal angles supplied by the
circumferentor.This eliminates any errors that
may be introduced by replacing one instrument
with another to take a vertical
angle. (A vernier
scale divides the master scale divisions into
fractions, thus adding an order of magnitude
increase in the accuracy of a
reading.) This book is the Surveyor's
lifeline. It tells him (and anybody else that reads
it) exactly what happened during a field survey. It
tells the reader the distance as well as the angles
(both horizontally and vertically). Frequently, the
field hand also recorded a wealth of other useful
data: the time of day, the temperature, the
weather, even other scientific oddities he found
along the way. This simple
device is made with a brass rod approximately 15
inches long and weighted at one end with
lead. It is used
to determine the exact location on the ground
directly under some important marker that is
above ground level., such as the center of the
circumferentor or theotolite. As such it, is
typically used to start a chain survey after the
tripod and compass have been positioned for the
first time. To use a
drop arrow, the surveyor places it precisely
under the marker (ie: the thumbscrew at the
bottom of the tripod plate) and when the point
settles down, he lets go. The weighted tip
insures that the arrow will drop straight and
that it penetrates into the ground below. Once
the ground location has been identified, the
first loop of the chain is staked, and
measurements can begin. Gunter's Chain is the most
widely known unit of measurement that is
universally attributed to the Art of Surveying. It
came into common usage about 1700 a.d. and was the
standard for measuring distances over 150 years.
Until early in the 20th Century, it was universally
made of iron or brass links. Because all of these
chains were hand made, they rarely measured exactly
the proscribed sixty six feet in length. Thus, the
surveyor had to use a correction factor when
translating his notes into a drawing. In later
years, it became the Surveyor's Tape that was
machine made and used sophisticated metallurgy to
compensate for the small (but measurable) effect of
temperature on the length of the tape. These chains are commonly
found in both the full (100 link) and half (50
link) lengths. This wrought iron device was
frequently used in the field to keep the chain from
tangling, thus speeding the process of measuring
distances. These stakes come in many
sizes and shapes. Their main function is to aid in
holding the chain in place while the chainsman
makes a change in direction. They can also be used
to identify temporary locations the need
arises. The Ring Dial is a
sophisticated advancement over the Astrolabe in
that it takes into account both the time of day and
the day of the year to determine one's latitude.
Conversely, if the latitude and the day of the year
are known, you can determine the time of day to an
accuracy of plus or minus five seconds.Of course,
this "time" is actually the local sun
time. A Chronometer is an
exceptionally accurate mechanical clock --
usually defined as having an error of not more
than five seconds a month. About one watch in
hundred would qualify and be priced accordingly.
As such, a chronometer could very easily cost
the surveyor or sea captain a year's
wages!
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