What is Land Surveying?
Surveying has traditionally been defined as the science and art of determining relative positions of points above, on, or beneath the surface of the earth, or establishing such points. In a more general sense, however, surveying can be regarded as that discipline which encompasses all methods of gathering and processing information about the physical earth and environment,. Conventional ground systems are now supplemented by aerial and satellite surveying methods, which evolved through the defense and space programs.
In general, the work of a surveyor can be divided into five parts:
1. Research analysis and decision making. Selecting the survey method, equipment, most likely corner locations, and so on.
2. Field work or data acquisition. Making measurements and recording data in the field.
3. Computing or data processing. Performing calculations based on the recorded data to determine locations, areas, volumes, and so on.
4. Mapping or data representation. Plotting measurements or computed values to produce a map, plat, or chart, or portraying the data in numerical or computer format.
5. Stakeout. Setting monuments and stakes to delineate boundaries or guide construction operations.
Surveying is one of the oldest and most important arts practiced by bman because from the earliest times it has been necessary to mark boundaries and divide land. Surveying has now become indispensable to our modern way of life.
Surveying continues to play an extremely important role in many branches of engineering. For example, surveys are required to plan, construct, and maintain highways, railroads, buildings, bridges, tunnels, canals, land subdivisions, seweage systems, pipelines, etc. All engineers must know the limits of accuracy possible in construction.
A little History on Surveying
The oldest historical records in existence today which bear directly on the subject of surveying state that this science had its beginning in Egypt. Herodotus says Sesostris (about 1400B.C.) divided the land of Egypt into plots for the purpose of taxation. Annual floods of the Nile River swept away portions of these plots,and surveyors were appointed to replace the bounds. These early surveyors were called rope-stretchers, since their measurements were made with ropes having markers at unit distances.
As a consequence of this work, early Greek thinkers developed the science of geometry. Their advanced, however, was chiefly along the lines of pure science. Hereon stands out prominently for applying science to surveying in about 120B.C. He was the author of several important treatises of interest to surveyors, including The Dioptra, which related the methods of surveying a field, drawing a plan, and making calculations. It also described one of the first piece of surveying equipment recorded, the Diopter. For many years Heron's work was the most authoritative among Greek and Egyptian surveyors.
Significant development in the art of surveying came from the practicalminded Romans, whose best-known writing on surveying was by Frontinus. Although the original manuscript disappeared, copied portions have been preeserved. This noted Roman engineer and surveyor, who lived in the first century, was a pioneer in the field and his esay remained the standard for many years.
The engineering ability of the Romans was domonstrated by their extensive construction work thoughout the empire. Surveying necessary for this construction resulted in the organization of a surveyors' guild. Ingenious instruments were developed and used.
One of the oldest Latin manuscripts in existence is the Codex Acerianus, written in about the sixth century. It contains an account of surveying as practiced by the Romans and includes several pages from Frontinus's treatise. The manuscript was found in the 10th century by Gerbert and served as the basis for his text on geometry, which was largely devoted to surveying.
During the middle ages, Greek and Roman science was kept alive by the Arabs. Little progress was made in the art of surveying, and the only writings pertaining to it were called "practical geometry."
Early civilizations asuumed the earth to be a flat surface, but by noting the earth's circular shadow on the moon during lunar eckopses and watching ships gradually disappear as they sailed toward the horizon, it was slowly deduced that the planet actually curved in all directions.
Determining the true size and shape of the earth has intrigued humans for centuries. History records that a Greek named Eratosthenes, about 220B.C. first attempted to compute its dimensions. He ascertained the angle subtending the meridian arc between Syene and Alexandria in Eqypt by measuring shadows cast by the sum at these cities. The arc length was found by multiplying the number of caravan days between Syene and Alexandria by the average daily distance traveled. From the angle and arc measurements, applying elementary geometry, Eratosthenes calculated the earth's circumference to be about 25,000 mi. Subsequent precise geodetic measurements using better instruments and a technique equivalent geometrically to Eratosthenes's have shown his value, though slightly too large, to be amazingly close to the current accepted one. Actually, of course, the earth approximates an oblate spheroid having an equatorial radius about 13.5 miles longer than the polar radius.
In the 18th and 19th centuries the aart of surveying advanced more rapidly. The need for maps and location of national boundaries caused England and France to make extensive surveys requiring accurate triangulation; thus geodetic surveying began. The U.S. Coast and Geodetic Survey was established by an act of Congress in 1807. Initially its charge was to perform hydrographic surveys and prepare nautical charts. Later its activities were expanded to include establishment of control monuments throughout the country.
Increased land values and the importance of exact boundaries, along with the demand for public improvements in the canal, turnpike, and railroad eras, bought surveing into a prominent position. More recently, the large volume of general construction, numerous land subdivisions with better records required, and demands posed by the fields of exploration and ecology have entailed an augmented surveying program. Surveying is still the sign of progress in the development and use of the earth's resources.
Progress continued into the space program where new equipment and systems were needed to supply precise control for missle alignment and moon mapping of proposed landing sites. Electronic distance-measuring (EDM) equipment, laser devices, north-seeking gyroscopes, improved aerial cameras, inertial and doppler surveying systems, remote sensors, and various-sized computers are but a few products of today's technology now being directly applied in modern surveying with terrific impact. Landsat spacecraft provide images of global coverage every 18 days for down-to-earth projects such as land cover inventories, natural resource mapping, water quality assessment, and flood control.