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CELEBRATING 101 YEARS
Survey Related Information
WHAT IS SURVEYING?
SURVEYING is the art of using scientific principles to make comparatively
large measurements to a required accuracy. Surveying has two basic
functions: (1) to measure what exists, to determine where it is
located, and usually to prepare a map to show the results of these
data from which a plan or a boundary description can be made;
and (2) to establish marks to guide construction according to
a plan or to show the boundaries according to a description or
other data.
Since no project of importance can be efficiently designed or
constructed without a map and survey control, surveying is an
essential part of nearly every field operation. Its use extends
from measuring property boundaries and making a plot plan for
a house to great construction projects like canals, railroads,
and highways. Even the placement of tracking devices for space
vehicles must be accurately located by surveys. The principles
of precision surveying are also used in optical tooling to control
the construction and alignment of large products like airplanes,
rockets, and turbines.
LAND - THEY ARE NOT MAKING ANY MORE OF IT
Real estate is unique. Land is real. You can feel it; you can
stand on it. It has a smell and a taste, and you can see and touch
it. In fact, fee simple to the land is called a "Corporeal
Hereditament," because it refers to something tangible. Title,
however, cannot be seen or felt. Personal possessions such as
a knife or a dollar bill can be seen and handled, can be traded,
sold, and otherwise disposed of (or even lost). Most often, ownership
is with the holder; therefore, it can be said that "title"
is really synonymous with "ownership." Along this line
of reasoning, the reader should be aware at all times that a deed
normally is not proof of title, but only evidence of title.
A QUESTION OF TITLE
Real estate cannot be moved, lost, or reshaped, but it can be
traded, sold, and disposed of by properly executed deeds or succession
of heirs, adverse possession, recognition and acquiescence, equitable
estoppel, parole agreement, failure to pay taxes, or other unwritten
acts. The important thing to remember is that any of the transactions
mentioned above involves the transfer of title to the land and
not a change of the land's location, size, shape, or any other
physical change. Title, being invisible and not subject to transfer
from person to person, must therefore be transferred by rules
that establish certainty of performance. These rules are set forth
in the laws of each state and, in general, are similar between
states. Most laws regarding transfer of title date back to the
ancient Livery of Seisin ceremony used to convey title prior to
the passage of the Statute of Frauds.
"There are several things necessary to make a valid transfer
of title, especially in the sale of land. We are primarily concerned
with the essential part of the transaction known as a deed.
THE DEED AND THE SURVEYOR
Land itself is the subject of the deed, and, without a written
document within which are set forth the terms of agreement, the
description (or identification) of the real estate, and the signatures
of the agreeing parties, as verified or acknowledged by a notary.
THE PURPOSE OF A LEGAL DESCRIPTION
The purposes of a legal description are to:
1. Identify the land for title purposes. In actuality, this is
really the only purpose of the deed description. The land itself
is the subject of the deed and, without a clear, unambiguous statement
of the location of such land, deed will be found void for want
of sufficiency, in the legal phrase.
2. Describe by words the exact location, geometric shape, and size of the land to be conveyed for the purposes of retracement by the subsequent resurvey or other interested parties.
TYPES OF SURVEYS
Geodetic control surveys. Control surveys provide the reference
Framework for lesser surveys. A traverse with elevations of its
points, may be the control for mapping a limited area. The broadest
control surveys are the National Geodetic Survey (NGS) in the
United States and by corresponding agencies in other countries,
wherein the horizontal and vertical positions of points are established
with first- or second-order accuracy.
In geodetic surveys. Earth curvature is taken into account. Coordinate
positions are established in terms of latitude and longitude.
Geodetic coordinates are convertible into state plane coordinates.
The traditional method of extending horizontal geodetic control
is triangulation. Trilateration and traverse are supplementary
techniques.
In geodetic surveys, refinements are added to the simple chain-of-triangles
scheme. The most notable refinement is use of the quadrilateral
as a geometric unit. Diagonal directions as well as the side are
observed, so that the quadrilateral includes two pairs of overlapping
triangles, one being redundant although valuable as a check. In
this way additions angular checks are available, and four separate
calculations can be made for the entering Side length of the next
quadrilateral in the chain.
Route surveys. Surveys for the design and construction of linear
works, such as roads, canals, pipelines, or railways, are called
route surveys. They begin with reconnaissance and continue through
preliminary, location, and construction surveys.
Reconnaissance for a new highway, for example, may be accomplished
by study of existing maps together with a visual appraisal of
field conditions, or even quick low-order horizontal and vertical
field measurements. Controlling points, such as favorable ridge
and river crossings, are found, and a preliminary line is selected.
This line traditionally is laid out by transit and tape or EDM,
being a linear traverse. It is profiled, that is, levels are run
along the traverse line to find elevations. Traverse profiles
(cross sections) are made at needed intervals. Structures and
natural objects that would affect the final location are fixed
by side shots. A side shot may be a direction and distance from
a transit point, the intersection of two directions or two distances,
or a perpendicular offset from a traverse line. Transverse profiles
are made by hand level, tape, and level rod.
The result of the preliminary survey is a strip topographic
map of sufficient precision to permit preliminary design
of the final location, including approximate determination
of earthwork quantities. More and more preliminary
maps and designs are executed from topographic maps
constructed by airborne photographic (photogrammetric) methods,
with need for only limited ground surveying prior to construction
layout.
The location survey line is conducted with at least
third-order precision. Traverse procedures are followed, but
curves are laid out and stationed. The result is a staked centerline
for the route to be constructed. Profile leveling and cross-sectioning
for earthwork quantities also are part of the location survey.
Construction surveys. Surveys for construction layout establish
systems of reference points that are not likely to be disturbed
by the work. Slope stakes are earthwork references. Buildings,
bridge abutments, sewers, and many other structures traditionally
are controlled by batter boards, horizontal boards fastened to
two uprights. The top of a batter board is set at the elevation
of the line to be established, and the horizontal position of
the line is indicated by a mark or nail. Across the site another
batter board is set up for the given line, and a string or wire
stretched between is the line. The line may be a building face
at first-floor level, or it may be a reference line. In trench
work the line between batter boards may run at a fixed distance
above the invert centerline.
In lieu of strings or wires, lines of sight may be used. A transit
is set up on lines outside the work area, and points of the line
are sighted as required. Further, a low-power laser, available
as an attachment to the transit or as a separate special purpose
instrument, can prefect a visible reference line or plane from
an unattended position. A means of locating critical construction
points, such as those for anchor bolts, is to compute their positions
in a coordinate grid, then compute directions and distances from
a reference point for their location by transit sighting and tape
measurement.
Elevation controls are provided by bench marks near the construction
area. The foregoing construction techniques are adaptable into
industrial plants for building large mock-ups and jigs as well
as for the alignment of parts. Transits and levels on stable mounts
may be used; however, related specialized equipment called optical
tooling instruments are more readily applied. These include a
transit or level telescope with an optical micrometer on the objective,
to move the line of sight to a locus parallel with the initial
sighting and flat self-reflecting mirrors for use as targets.
Angular sight lines are established by a mirror mounted vertically
on a transit base.
Underground surveys. Mine and tunnel surveys impose a few modifications
on normal surveying techniques: Repeated independent measurements
are made because normal checks (such as closed traverses) are
not available; cross hairs illuminated because work is performed
in relative darkness: vertical tape measurements and trigonometric
levels, instead of differential levels, frequently must be relied
upon; and in adits and tunnels survey points are placed overhead,
rather than underneath, to save them from disturbance by traffic.
On the mining transit, an auxiliary telescope outside the trunnion
bracket facilitates steep sightings.
Traditionally the most exciting underground survey process has
been the transferring of a direction from the surface. In shallow
shafts, steep (but not vertical) sights may transfer the direction.
Another technique is to hang two weighted wires down the shaft,
observe the direction between them on the surface, and use this
direction as a control below. The relative shortness of distance
between wires makes the transfer geometrically weak, but procedural
care enables satisfactory results. An alternative procedure applies
inertial navigation principles to underground surveying. A north-seeking
gyro mounted on a transit gives azimuth accuracy to about 6 seconds
from a [climbed position at shaft bottom and carries tunnel lines
forward without the angle-error accumulation in ordinary transit
traverse lines.
Hydrographic surveys. Data for navigation charts and underwater
construction are provided by hydrographic surveys. The horizontal
locations of depth measurements must be referenced to recognizable
controls. Where the shoreline is visible, it is mapped and a system
of triangulation stations is established on shore. Transits at
two triangulation stations can be used to observe directions to
the sounding vessel whenever it signals that a depth measurement
is made. A check angle may be obtained by sextant observation
of shore points from the deck of the vessel, or a third transit
on shore may be used to provide a check intersection. Angular
observations from a shore point, coupled with EDM lengths to the
sounding vessel reflector or transponder, will also fix the sounding
location. In another procedure, a sending microwave unit on the
vessel can find distances from slave stations set on shore points,
to be recorded (even plotted) instantly along with the depth sounded.
Cadastral surveys. To establish property boundary lines, cadastral
surveys are made. Descriptions based on horizontal surveys are
essential parts of any document denoting ownership or conveyance
of land. The basic rule of property lines and corners is that
they shall remain in their original positions as established on
the ground. This basis rule is important because most land surveys
are resurveys. They may follow the original description, but this
description is merely an aid to the discovery of the originally
established lines and corners. Substantial discrepancies are frequently
found in original descriptions because low-order surveying devices
such as the compass or the link chain were once used.
Surveys in the original 13 states, plus Tennessee, Kentucky, and
parts of others, are conducted on the metes and bounds principle.
In the so-called public land states and in Texas, the basic subdivisions
are rectangular.
If the boundaries to be described border an irregular line, such
as a winding stream, a good mathematical description may he impossible.
Such a line can, however, be located by a series of closely spaced
perpendicular offsets from an auxiliary straight line.
In the rectangular system, the land parcels of a region
are described by their relationship to an initial point. In public-land
states the initial point is the intersection of a meridian
(principal meridian) and a latitude (baseline). Townships, normally
36 square miles, are designated by their position with respect
to the initial pointthe number of tiers north or south of
a given baseline and the number of ranges east or west of the
corresponding principal meridian.
Within the township each square mile, or section, has a number,
from I to 36. Sections are subdivided into quarter sections (
160 acres or 0.6-175 km2), and they may he subdivided further.
North-south section lines are meridians originating at 1 mile
intervals along the baseline and along standard parallels of latitude
(correction lines) generally spaced 24 miles apart. The respacing
of meridional lines every 24 miles reduces the effect of meridian
convergence on the size of sections.
Resurveys become difficult where the corners are obliterated or
lost. An obliterated corner is one for which visible evidence
of the previous surveyor's work has disappeared, but whose original
position can be established from other physical evidence and testimony.
A corner is deemed lost when no sufficient evidence of its position
can be found. Restoration requires a faithful rerun of the recorded
original survey lines from adjacent points, distance discrepancies
being adjusted proportionately.
HISTORY OF SURVEYING
The Great Pyramid of Khufu at Giza, built about 2700 B.C., is
so accurately square and so perfectly oriented to the cardinal
points of the compass that it is evident that the Egyptians
used surveying as means of controlling construction just as we
do today. Surveying also was used to determine property lines,
as Sumerian clay tablets (1400 B.C.) show records of land measurement
and plans of cities and nearby agricultural areas. Boundary stones
marking property corners have been preserved, and there is representation
of land measurement of the Menna at Thebes (1400 B.C.) showing
two men chaining a wheat field with what appears to be II a cord
with knots!) at regular intervals. The head chainman carries an
extra length of cord, and the rear chainman has gathered up the
rear end.
The Egyptians used an instrument called a gromma to establish
right angles. It was a wooden cross with a plumb bob) hanging
from the end of each of the four arms. it was supported by a cord
at its center. The Egyptians also had a levelan A-frame
with a plumb bob supported by a cord at the peak of the A, the
plumb bob hanging past an index marked on the bar of the A. With
these instruments the ancient Egyptians were able to measure land
areas, record the positions of boundary markers, and build the
huge Pyramids to very exact dimensions.
The Romans, who were in Egypt from 30 B.C. to 642 A.D., slightly
improved the Egyptian devices and added a water level and a plane
table with a crude alidade to the list of instruments available
for surveying. The water level was either a wooden trough filled
with water, or it was a tube with its ends turned up. It must
have been quite accurate, since a level would be essential in
building the Roman aqueducts.
A crude odometer for distance measurements was introduced in 30
B.C. by the Roman architect Vitruvius. It consisted of a device
like a wheelbarrow, with a wheel of known circumference that automatically
dropped a pebble into a container at each revolution.
The Greek astronomer and mathematician Hipparchus is credited
with the development of trigonometry about 130 B.C. When the Scottish
mathematician John Napier invented logarithms about 1614, 17 centuries
later, and logarithmic tables were published in 1620, portable
angle-measuring instruments became important and surveying took
a long step forward. These instruments were called "topographical"
instruments or "theodolites." They had a hand-divided
circle and a pivoted arm for sighting and were capable of measuring
horizontal and vertical angles. Some may have had magnetic compasses,
which had been developed about 1511 by Martin Waldseemuller.
Distances were measured with wooden rods or by cords called "Furlongs."
A furlong is 66 feet long, and four rods equaled one furlong.
Ten square furlongs equals one acre.
Levels basically were improved Roman water levels, but about 1704
Rowley built a spirit level. Lacking telescopic sights, he used
a sighting device about 1 meter long to gain accuracy.
Edmund Gunter introduced his famous chain, 66 feet (20.3 meters)
long and composed of 100 links, in 1620.
The development of the circle-dividing engine by the British instrument
maker Jesse Ramsden about 1775 produced one of the greatest
advances in surveying methods. Heretofore it had been impossible
to measure angles accurately with a portable instrument.
The vernier, developed by the French mathematician Pierre Vernier
in 1631, the micrometer microscope developed by William Gascoigne
in 1638, the telescopic sight probably developed by the French
astronomer Jean Picard in 1669, and the spirit level were all
available to be incorporated in the theodolite of Jonathan Sisson
about 1720. Stadia hairs were first applied by James Watt in 1771.
Spirit levels were equipped with telescopic sights about this
time.
SURVEYING INSTRUMENTS
Instruments used in surveying operations to measure vertical angles,
horizontal angles, and distance. The devices used for these measurements
were originally mechanical only, but advances in the technology
led to the development of mechanical-optical devices, optical-electronic
devices, and finally, electronic-only devices.
Level, Four types of levels are available: optical, automatic,
electronic, and laser.
Optical level. An optical level is used to project a line of sight
that is at a 90 degree angle to the direction of gravity. Both
types, dumpy and tilting, use a precision leveling vial to orient
to gravity. The dumpy type was used primarily in the United States,
while the tilting type was of European origin and used in the
remainder of the world. The dumpy level has the leveling vial
fixed to the telescope, which is fixed at 90 degrees to a rotatable
vertical spindle. Leveling screws, attached to the spindle, are
used to center the leveling vial.
Automatic level. Automatic levels use a pendulum device,
in place of the precision vial, for relating to gravity. The pendulum
mechanism is called a compensator. The pendulum has a prism
or mirror, as part of the telescope, which is precisely positioned
by gravity. The pendulum is attached to the telescope by using
precision bearings or wires (metallic or nonmetallic). Leveling
screws are used to roughly center a circular vial, and the optics
on the pendulum then correct the line of sight through the telescope.
Automatic levels are easy and last to use, resulting in their
domination of the optical-level market segment.
Electronic level. This type of instrument has a compensator
similar to that on an automatic level. but the graduated leveling
stall is not observed and read by the operator. The operator has
only to point the instrument at a bar-code-type staff, which then
can be read by the level itself. The electronic determination
of the data is a further advantage because the data can lie transferred
to a data collector or stored on-board in a memory module or card.
The electronic level eliminates human reading error and increases
the speed at which leveling work can be performed. The only significant
disadvantage is the high cost as compared to the optical automatic
level.
Laser level. Although this type of instrument is categorized
as laser, these levels actually employ three different types of
light sources: tube laser, infrared diode, and laser diode. The
instrument uses a rotating head to project the laser beam in a
level 360 degree plane. The advantages are twofold: no operator
is required once the instrument is set up; and different people
in various locations can work by using a single light source.
The disadvantages are that accuracy is less than that provided
by other types of levels and that the cost is significantly higher.
This type of instrument is used primarily for construction surveying.
Tube lasers have a visible beam with high power requirements.
The power source is usually a 12-V car battery or an AC-to-DC
converter. Infrared diode units have a nonvisible beam that can
operate on flashlight batteries. The nonvisible beam requires
that an electronic detector be used to "see" it. This
instrument has a lower cost than tube lasers, and is physically
smaller. The laser diode level has all the advantages
of the other two types: low power requirement, small size,
and visible beam.
There are three different mechanisms used to level-up laser
levels. Leveling vials were used initially, and they are
still used on the most inexpensive units. Moderate- to
mid-priced units employ compensators. For the higher-priced
units, electronic vials with servomotors mechanically
level the mechanism inside the case. Servo types are also available
in models that can tilt the rotating beam to a particular percent
of grade. Dual-grade instruments, the most expensive type, can
project two different grades at the same time. For example, (+)3%
in the north direction and (-)5% in the east direction.
Transit. The primary purpose of a transit is to measure
horizontal and vertical angles. Circles, one vertical and one
horizontal, are used for these measurements. The circles are made
of metal or glass and have precision graduations engraved or etched
on the surface. A vernier is commonly used to improve the accuracy
of the circle reading.
The vertical circle, fixed to a horizontal axis that is part of
and at 90 degrees to a telescope, lets the telescope rotate in
a vertical plane. The alidade, or the framework that supports
the telescope axis, has a vertical axis (spindle) attached to
its base, which allows the alidade to rotate with respect to the
horizontal circle. Level vials, attached to the alidade, are used
to make the spindle vertical (in line with gravity), so that measurement
of horizontal angles can be measured. A level vial is also attached
to the telescope and provides the gravity index to measure vertical
angles.
Theodolite. The theodolite serves the same purpose as the
transit, and they have many similar features. The major differences
are that the measuring circles are constructed only of glass and
are observed through magnifying optics to increase the accuracy
of angular readings. Theodolites are generally smaller than transits.
Some models have a compensator, which allows quicker set-ups while
maintaining vertical angle accuracy. Theodolites also have a separate,
low-power telescope to view the setup point on the ground. This
telescope replaces the use of a plumb bob to position the instrument
over a point. Optical theodolites largely replaced transits but
then they were replaced by electronic theodolites.
The electronic theodolite uses electronic reading circles
in place of the optically read ones. The circle readings are observed
on a display located on the alidade. Some versions of this instrument
can transmit the electronic readings via a serial port to an external
data memory device or to an electronic distance meter attached
to the theodolite.
Electronic distance meter. Electronic distance meters use
either light waves or radio waves as their measuring device. Radio-wave
instruments dominated this category until the late 1960's, when
lower-cost light-wave instruments became available.
Radio-wave instruments require similar units placed at
each end of the line to be measured, are capable of longer measurements
(up to 90 mi or 140 km), and do not require a direct line of sight
between the units; however. they are more sensitive to atmospheric
conditions.
Light-wave instruments use visible, laser, or infrared
light. Only one unit is required, with the other end of the measured
line occupied by a special type of prism reflector. Measurements
are more precise, distance capability is shorter (up to 40 mi
for laser and 6 mi for infrared), and a direct line of sight is
required between the unit and the reflectors.
These instruments provide more stable results. Accuracy has improved
to the degree that a basic accuracy of ±2 mm is commonly
achieved. These instruments typically use several frequencies
and phase-comparison techniques to determine distance, not time
measurement.
Total stations. These units consist of combinations of
devices, which can be optical, electronic, data-electronic, or
motorized electronic.
Optical. The combination of a theodolite and an infrared
electronic distance meter into one instrument is commonly referred
to as an optical total station. The configuration can be one integrated
unit, or it can be modular in design. Integrated types typically
have longer-range distance capabilities matched
with higher angle accuracy. Modular-types can have any
combination of short- to long-range distance measuring matched
will) low-to-high angle accuracy.
Electronic. An electronic total station comprises an electronic
theodolite in combination with an infrared electronic distance
meter. This type of instrument has become the standard surveying
instrument, having replaced all earlier angle and distance instruments
for most applications. Compensators are common on these instruments,
and many models have dual-axis types that correct for misleveling
in both directions. Some units have been developed that have many
useful programs built in. The category of electronic total station
includes models that serve virtually all survey needs, and less
expensive models have been designed specifically for use in construction.
These instruments are very efficient when used alone, and the
addition of a data collector, replacing hand-written notes, is
the next step in a fully electronic system. The data collector
reduces mistakes in the Field and can perform some useful calculation
functions quickly and easily. The final component is the office
computer to which the data collector can transfer the information.
Through the use of specialized surveying software, maps are generated
by a plotter or printer.
Data electronic. Miniaturization of electronic components
made it possible to combine an electronic total station with the
data collector. Small removable modules or cards are used to store
the data, which can subsequently be transferred to the office
computer. These models provide a one-piece instrument, eliminating
cables and facilitating transport. Some models have full alphanumeric
keyboards so that descriptions and notes can be added to the measured
data. Special units have been designed that use custom programs.
Motorized electronic. This type of electronic total station
has two characteristics that distinguish it from the standard
type. The manual alignment mechanisms are replaced by motors,
and the optical telescope is replaced by an electronic type. The
instrument can align itself to the prism reflector, thus eliminating
the instrument operator. Data recording can be initiated remotely
by the reflector operator, making the process a one-person operation.
This reduction in personnel is the primary advantage of this system.
Global Positioning System. The lie U.S. Department of Defense
installed a satellite system for navigation and for establishing
the position of planes, ships, vehicles, and so forth. This system
uses special receivers and sophisticated software to calculate
the longitude and latitude of the receiver. It was
discovered early in the program that the distance between two
non moving receivers could be determined very accurately
and that the distance between receivers could be many miles apart.
This technology has become the standard for highly accurate control
surveys, but it is not in general use because of the expense of
the precision receivers, the time required for each setup, and
the sophistication of the process.
Mapping of city features such as systems for supplying water,
sewage collection, and electricity does not require the precision
of normal surveying. Low-cost, low-precision receivers are used
for this purpose, and cities are able to have cost-effective multi
layer databases that contain all of the city structure located
below and above the ground.