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.
WHY DO YOU NEED A SURVEY?
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
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.
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.