Articles
Helpful information about the basics of surveying

The History of the Dividing Engine

Posted on by OgilvieGeomatics

The invention of the circular dividing engine was an important moment for surveying. The measurement inscriptions on instruments such as the compass had previously been made by hand, which meant their accuracy varied considerably. The dividing engine eliminated the problem of human error and paved the way for instruments with a consistently high degree of accuracy to be produced.


Exactly when and by whom the first dividing engine was made remains unclear, but one of its first creators was undoubtedly clockmaker Henry Hindley, in around 1739. His instrument was based on a gear-cutting machine for clockworks, and used a worm-gear and toothed index gear-plate to operate the mechanism.



Sometime between 1765 and 1768, Duc de Chaulnes produced a pair of dividing engines for dividing circular arcs and linear scales, which were also inspired by clockmaking. Chaulnes’ goal was to improve the accuracy of instruments by removing the danger of human error wherever possible.

In 1773, Jesse Ramsden produced a dividing engine with a screw-cutting lathe which was a significant improvement on previous designs. Ramsden received funding for his dividing engine from the Board of Longitude, on the condition that his design would not be patented, and he would teach others to create their own.

Following the invention of the dividing engine, the UK had a near-monopoly on the precision instrument industry, as other countries failed to produce anything as accurate as the instruments based on Ramsden’s creation. In the early 1800s, American surveying instrument specialist William J Young created a larger dividing engine, which he claimed allowed an even greater degree of precision. He modified his dividing engine so it could be operated automatically. Later, he produced a circular dividing engine with a 48-inch radius, which was used in the graduation of scales for engineers’ transits and other instruments.

The instruments produced with Young’s automatic dividing engine played a key role in the exploration and colonisation of the American West. The dividing engine made it possible to produce more accurate surveyors’ compasses, and a number of other valuable instruments, including the railroad compass, which was widely used as railway lines were laid across the U.S. Later, the surveyor’s transit was developed by replacing its sighting bars with a telescope which could be revolved on its horizontal axis. Young’s transit achieved widespread popularity among surveyors shortly after the launch of its commercial production, in the mid-1800s.

Christian Louis Berger also played an important role in the development of the dividing engine. In 1871, after a number of years working with some of the world’s best instrument makers, he and George L Buff established Buff and Berger, producing instruments for surveying, engineering, mining and science. The pair developed a reputation for producing high-quality precision instruments, until the firm was dissolved in 1898, following a dispute. After acquiring the company’s assets, Berger and his sons moved the business to Roxbury, Massachusetts, where they produced instruments for geodetic, civil, geological and petroleum surveyors internationally. With their highly accurate dividing engines, this was perhaps the company’s most productive period, and the company remained influential until it was eventually sold, in 1948.

 

The History of GPS

Posted on by OgilvieGeomatics

The Global Positioning System, or GPS, is a network of satellites which transmit signals to receivers on the ground while they orbit Earth. The signals have a time code and geographical date which enables users to identify their location with a high degree of accuracy. Since GPS was made available for non-military purposes, it has become an essential surveying tool. GPS was initially created as an intelligence and military tool during the Cold War. On October 4, 1957, MIT scientists studying the Russian satellite known as Sputnik noticed that its radio signal grew as it approached and diminished as it got further away – a phenomenon known as the Doppler Effect.

The scientists’ observations of Sputnik inspired them to track satellites from the ground by measuring the frequency of their radio signals, and track the location of receivers on the ground by measuring their distance from the satellites. This is the foundation of the principle behind the GPS receivers used in cars, phones and various industries, including surveying. In 1959, the U.S Navy created TRANSIT, a satellite navigation system which was designed to track submarines, initially with six satellites and later, 10. Although the system was slow compared to today’s systems, TRANSIT paved the way for the development for GPS. In 1963, the Aerospace Corporation carried out a study into the possibility of creating a system of space satellites which would send continuous signals to receivers on the ground. The study, which was completed for the U.S Military, laid the conceptual foundations for today’s GPS, with satellites capable of tracking fast-moving vehicles on the ground and in the air, and generating highly accurate location coordinates by recording the transmission times of signals sent from space satellites.

The first test satellite of the proposed 24-satellite system NAVSTAR was launched by the Military in 1974, following 11 years of work on the project. From 1978 to 1985, 11 NAVSTAR test satellites were launched, with on-board atomic clocks to precisely measure transmission times. In 1989, following years of intensive testing, the Air Force released the first fully functioning GPS satellite into space, using the Delta II Rocket.

The Magellan NAV 1000, which was claimed to be the first hand-held navigation device using GPS, went on the market in 1989. But a year later, the U.S Defence Department intentionally lowered the accuracy of GPS, amid concerns that adversary nations may find a way of using it to their advantage.

In 1995, the last of 27 GPS satellites was released into space, three of which were spares to replace any of the 24 active satellites, should they develop a fault. The 3,000-4,0000-pound satellites circled Earth twice per day.

Plans for the transmission of two additional GPS for non-military use were announced in 1998, and shortly afterwards, in 2000, the Defence Department’s intentional diminishment of the system’s accuracy was ended – and GPS became ten times more accurate. Before long, GPS was an important tool in a range of industries, from fishing to surveying. GPS technology quickly became cheaper and more compact, and an array of products, such as vehicle navigation devices, were soon on the market.

The History of the Spirit Level

Posted on by OgilvieGeomatics

Spirit levels are used in surveying, carpentry, construction and other professions to identify whether a surface is horizontal or vertical. In their early days, they included curved, glass vials with continuous inner-diameter at each viewing point. The vials were partially filled with liquid – usually alcohol or a coloured sprit – leaving a bubble in the tube. The vials’ subtle upward curve caused the bubble to rest in the middle, at the highest point. The bubble reacted to any inclination by moving away from the center position. 


Alcohols such as ethanol are often used in spirit levels, due to their low surface tension and viscosity, which allows the bubble to move quickly through the tube and settle accurately, with minimal interference.

The bull’s eye level is a circular, flat-bottomed device with liquid underneath a convex glass face, with a circle at the center. Unlike a standard level, a bull’s eye level can be used to level a surface across a plane – rather than only in the direction of the tube.

The sprit level was invented by Melchisedech Thevenot, a wealthy amateur scientist and royal librarian to Louis XIV of France. Examination of correspondence between Thevenot and scientist Christiaan Huygens has revealed that the spirit level was invented at some point before February 2, 1661. Thevenot quickly released a description of his creation to others around Europe, including Vincenzo Viviani, in Florence, and Robert Hooke, in London. Exactly when use of the spirit level in land surveys and other projects became widespread remains unclear, with some arguing that they did not gain popularity until the 18th century, since it is from this period that the oldest surviving examples date. However, there are records of the Academie Royale des Sciences being advised to take “levels of the Thevenot type” on their expedition to Madagascar, in 1666.

The modern level with a single vial was invented by Henry Ziemann, in the 1920s and, in 1939, William B. Fell created the Fell All-Way precision level, in Rockford, Illinois. This bull’s eye level could be positioned on a machine bed and display tilt on the x-y axes, making it unnecessary to rotate the level 90 degrees. Compared to previous designs, Fell’s level was remarkably accurate, and set a new standard of .0005 inches per foot resolution.

Production of the Fell All-Way precision level ceased in around 1970, and was resumed in the ‘80s by Thomas Butler Technology, in Rockford, Illinois, before finally ending in the ‘90s. The spirit level remains an important tool for surveying and various other industries, and has been incorporated into the design of a number of other tools. The dumpy level, which is used to measure height differences over larger distances, often features an inbuilt spirit level. It was invented in 1832, by English civil engineer, William Gravatt. Commissioned to examine a railway route from London to Dover, he devised the dumpy level as a more mobile and easier-to-use alternative to the Y level.



The History of the Compass

Posted on by OgilvieGeomatics

The most common type of compass has a magnetised needle which points to magnetic north and south by rotating to align with Earth’s magnetic field. Exactly when the principles underlying the magnetic compass were discovered remains unclear. There is evidence that the Ancient Greeks grasped magnetism, and as much as 2,000 years ago, Chinese scientists may have understood that it was possible to temporarily magnetise an iron bar by rubbing it against a lodestone, so it would point north and south.

The first compasses consisted of a magnetised needle attached to a piece of wood which floated in a container of water. As the needle settled, it would point in the direction of magnetic north and magnetic south. As scientists’ and engineers’ understanding of magnetism progressed, the needle of the compass was mounted on a card which displayed north, east, south and west. A spearhead accompanied by the letter ‘t’ (standing for the Latin name for the north wind, Tramontana) signified north. The compass card continued to develop, until all 32 directions were displayed. China may have developed compasses as early as the 11th century, closely followed by western Europe, in the 12th century. It is likely that these rudimentary compasses were used when more traditional means of determining direction, such as the moon or stars, were obscured.

By the 15th century, a discrepancy between the ‘north’ indicated by magnetic compasses and Earth’s actual geographic north had been identified. The difference between magnetic north and actual north became known as ‘variation’ or ‘magnetic declination’. It differs depending on the user’s proximity to Earth’s poles; variation is at its minimum on the equator, but is significantly greater near the south and north poles, where compasses must be adjusted to avoid misleading directions.

There is evidence of magnetic compasses having been used for building orientation in Denmark during the 12th century. A fourth of the country’s Romanesque churches are rotated by 5-15 degrees clockwise from east to west, which corresponds with the predominant variation at their time of construction – indicating that the use of magnetic compasses was already reasonably widespread during this period.

When shipbuilders started using iron and steel instead of wood, it was discovered that ships can affect the reading of their on-board compass – a phenomenon known as ‘deviation’. It became common to place iron balls or bars close to the compass to increase its accuracy. Deviation is also taken into account on aircraft, the metal of which can affect compass readings.

Not all compasses use Earth’s magnetism to indicate direction. The gyrocompass, which was invented in the 20th century, has a rotating gyroscope to follow Earth’s axis of rotation in order to point northwards. Variation is not an issue for the gyrocompass, which is widely used on aircraft and ships.

Although global positioning systems (GPS) have become increasingly popular in recent years, the compass remains an important tool in various industries, including surveying, and for a range of recreational activities.

 

The History of the Theodolite

Posted on by OgilvieGeomatics

The theodolite is a precision instrument for measuring horizontal and vertical angles. Mounted on adjustable legs and with a swiveling telescope, the modern theodolite is used to record detailed measurements for triangulation in road construction and other civil engineering projects.

Before the invention of the theodolite, various tools such as graduated circles and semicircles, and geometric squares, were used to measure either vertical or horizontal angles. German writer Gregorius Reisch described a devise which was capable of measuring both angles simultaneously in Margarita Philosophica, which was published in 1512.

In 1571, English surveyor and mathematician Leonard Digges used the term ‘theodolitus’ in Pantometria, his book on measurement, to describe a surveying instrument with a circular ring divided into 360 degrees, and a pivoting alidade with sight vanes at each end. This rudimentary theodolite became popular among surveyors in England, and in 1791, writer and mathematical instrument maker George Adams described the instrument as a ‘common theodolet’, using ‘theodolite’ only for telescopic instruments with vertical arcs and horizontal circles.

The first theodolite capable of measuring horizontal angles with geodetic accuracy was made in London by mathematician and scientific instrument maker Jesse Ramsden, in the late 1700s. He created the Great Theodolite for the Royal Society, which had decided to link the Royal Observatory in Greenwich with the Observatory in Paris, by means of triangulation. Ramsden designed a highly accurate dividing engine for his theodolite, which incorporated a horizontal circle which was three feet in diameter and weighed approximately 200 pounds. Ramsden’s Great Theodolite is now housed at the Greenwich Museum, in London.

Use of the telescopic theodolite became widespread among English surveyors but in America, the preference for the cheaper and more robust surveyor’s compass and surveyor’s transit endured. In the 18th century’s commonest design, the telescope was mounted on the theodolite’s vertical arc. In the 1840s, the transit theodolite was introduced in London, featuring a transit-mounted telescope, with a vertical circle on one edge. During the late 1800s, American inventor and physicist Edward Samuel Ritchie created a water-based theodolite, which the U.S Navy used to record the first precision surveys of the Gulf and Atlantic coast’s harbours.

The next major step in the development of the theodolite took place in Switzerland, in the 1920s, when inventor and designer Heinrich Wild introduced the optical theodolite, with a number of improvements on previous models, including an auxiliary telescope which made it possible to read either circle without leaving the station.

Theodolites remain an important tool in surveying. Various specialised models are available, including the photo-theodolite, which incorporates a camera and theodolite, mounted on one tripod, and is used for a range of projects, including the production of maps. Today, the reading of a theodolite’s vertical and horizontal circles is generally carried out with a rotary encoder, while CCD sensors have been added to the telescope’s focal plane, making an even greater degree of surveying precision possible.

 

test

Client Login

Locations

Accreditations:

Ogilvie Geomatics RICS

Ogilvie Geomatics ICES

Ogilvie Geomatics Construction Line

Ogilvie Geomatics The Survey Association

Ogilvie Geomatics SGS accreditation

Ogilvie Geomatics Audit Stamp

Cookie policy

We use cookies, just to track visits to our website, we store no personal details.

I understand