Surveying Equipment

As late as the 1990s the basic tools used in planar surveying were a tape measure for determining shorter distances, a level for determine height or elevation differences, and a theodolite, set on a tripod, with which one can measure angles (horizontal and vertical), combined with triangulation. Starting from a position with known location and elevation, the distance and angles to the unknown point are measured. A more modern instrument is a total station, which is a theodolite with an electronic distance measurement device (EDM) and can also be used for leveling when set to the horizontal plane. Since their introduction, total stations have made the technological shift from being optical-mechanical devices to being fully electronic with an onboard computer and software. Modern top-of-the-line total stations no longer require a reflector or prism (used to return the light pulses used for distancing) to return distance measurements, are fully robotic, and can even e-mail point data to the office computer and connect to satellite positioning systems, such as a Global Positioning System (GPS). Though GPS systems have increased the speed of surveying, they are still only horizontally accurate to about 20 mm and vertically accurate to about 30-40 mm.As well GPS systems do not work in areas with dense tree cover. It is because of this that total stations have not completely phased out earlier instruments. Robotics allows surveyors to gather precise measurements without extra workers to look through and turn the telescope or record data. A faster way to measure (no obstacles) is with a helicopter with laser echolocation, combined with GPS to determine the height of the helicopter. To increase precision, beacons are placed on the ground (about 20 km apart). This method reaches a precision of about 5 mm.

Surveying techniques

Historically, distances were measured using a variety of means, such as chains with links of a known length, for instance a Gunter's chain or measuring tapes made of steel or invar. In order to measure horizontal distances, these chains or tapes would be pulled taut according to temperature, to reduce sagging and slack. Additionally, attempts to hold the measuring instrument level would be made. In instances of measuring up a slope, the surveyor might have to "break" (break chain) the measurement- that is, raise the rear part of the tape upward, plumb from where the last measurement ended.
Historically, horizontal angles were measured using a compass, which would provide a magnetic bearing, from which deflections could be measured. This type of instrument was later improved upon, through more carefully scribed discs providing better angular resolution, as well as through mounting telescopes with reticles for more precise sighting atop the disc (see theodolite). Additionally, levels and calibrated circles allowing measurement of vertical angles were added, along with verniers for measurement down to a fraction of a degree- such as a turn-of-the-century transit.
The simplest method for measuring height is with an altimeter — basically a barometer — using air pressure as an indication of height. But for surveying more precision is needed. Toward this end, a variety of means, such as precise levels, have been developed. Levels are calibrated to provide a precise plane from which differentials in height between the instrument and the point in question can be measured, typically through the use of a vertical measuring rod.
With the triangulation method, one first needs to know the horizontal distance to the object. If this is not known or cannot be measured directly, it is determined as explained in the triangulation article. Then the height of an object can be determined by measuring the angle between the horizontal plane and the line through that point at a known distance and the top of the object. In order to determine the height of a mountain, one should do this from sea level (the plane of reference), but here the distances can be too great and the mountain may not be visible. So it is done in steps, first determining the position of one point, then moving to that point and doing a relative measurement, and so on until the mountaintop is reached.

Origin Surveying

Surveying techniques have existed throughout much of recorded history. In ancient Egypt, when the Nile River overflowed its banks and washed out farm boundaries, boundaries were re-established through the application of simple geometry. The nearly perfect squareness and north-south orientation of the Great Pyramid of Giza, built c. 2700 BC, affirm the Egyptians' command of surveying.

1. The Egyptian land register (3000 BC).

2. A recent reassessment of Stonehenge (c.2500 BC) indicates that the monument was set out by prehistoric surveyors using peg and rope geometry.

3. Under the Romans, land surveyors were established as a profession, and they established the basic measurements under which the Roman Empire was divided, such as a tax register of conquered lands (300 AD).

4. The rise of the Caliphate led to extensive surveying throughout the Arab Empire. Arabic surveyors invented a variety of specialized instruments for surveying, including.

• Instruments for accurate levelling: A wooden board with a plumb line and two hooks, an equilateral triangle with a plumb line and two hooks, and a reed level.
• A rotating alhidade, used for accurate alignment.
• A surveying astrolabe, used for alignment, measuring angles, triangulation, finding the width of a river, and the distance between two points separated by an impassable obstruction.

5. In England, The Domesday Book by William the Conqueror (1086)

• covered all England
• contained names of the land owners, area, land quality, and specific information of the area's content and habitants.
• did not include maps showing exact locations.

6. Continental Europe's Cadastre was created in 1808

• founded by Napoleon I (Bonaparte), "A good cadastre will be my greatest achievement in my civil law", Napoleon I
• contained numbers of the parcels of land (or just land), land usage, names etc., and value of the land
• 100 million parcels of land, triangle survey, measurable survey, map scale: 1:2500 and 1:1250
• spread fast around Europe, but faced problems especially in Mediterranean countries, Balkan, and Eastern Europe due to cadastre upkeep costs and troubles.

A cadastre loses value if register and maps are not constantly updated.

Large-scale surveys are a necessary pre-requisite to map-making. In the late 1780s, a team from the Ordinance Survey of Great Britain, originally under General William Roy began the Principal Triangulation of Britain using the specially built Ramsden theodolite.

What's u know about Land Surveying

Surveying is the technique and science of accurately determining the terrestrial or three-dimensional space position of points and the distances and angles between them. These points are usually, but not exclusively, associated with positions on the surface of the Earth, and are often used to establish land maps and boundaries for ownership or governmental purposes. In order to accomplish their objective,surveyors use elements of geometry, engineering, trigonometry, mathematics, physics, and law.
An alternative definition, per the American Congress on Surveying and Mapping (ACSM), is the science and art of making all essential measurements to determine the relative position of points and/or physical and cultural details above, on, or beneath the surface of the Earth, and to depict them in a usable form, or to establish the position of points and/or details.
Furthermore, as alluded to above, a particular type of surveying known as "land surveying" (also per ACSM) is the detailed study or inspection, as by gathering information through observations, measurements in the field, questionnaires, or research of legal instruments, and data analysis in the support of planning, designing, and establishing of property boundaries. It involves the re-establishment of cadastral surveys and land boundaries based on documents of record and historical evidence, as well as certifying surveys (as required by statute or local ordinance) of subdivision plats/maps, registered land surveys, judicial surveys, and space delineation. Land surveying can include associated services such as mapping and related data accumulation, construction layout surveys, precision measurements of length, angle, elevation, area, and volume, as well as horizontal and vertical control surveys, and the analysis and utilization of land survey data.
Surveying has been an essential element in the development of the human environment since the beginning of recorded history (ca. 5000 years ago) and it is a requirement in the planning and execution of nearly every form of construction. Its most familiar modern uses are in the fields of transport, building and construction, communications, mapping, and the definition of legal boundaries for land ownership.