Surveying or land surveying is the technique and science of determining the terrestrial or three-dimensional positions of points and the distances and angles between them. A land surveying professional is called a land surveyor; these points are on the surface of the Earth, they are used to establish maps and boundaries for ownership, such as building corners or the surface location of subsurface features, or other purposes required by government or civil law, such as property sales. Surveyors work with elements of geometry, regression analysis, engineering, programming languages, the law, they use equipment, such as total stations, robotic total stations, theodolites, GNSS receivers, retroreflectors, 3D scanners, handheld tablets, digital levels, subsurface locators, drones, GIS, surveying software. Surveying has been an element in the development of the human environment since the beginning of recorded history; the planning and execution of most forms of construction require it. It is used in transport, communications and the definition of legal boundaries for land ownership.
It is an important tool for research in many other scientific disciplines. The International Federation of Surveyors defines the function of surveying as: A surveyor is a professional person with the academic qualifications and technical expertise to conduct one, or more, of the following activities. Surveying has occurred since humans built the first large structures. In ancient Egypt, a rope stretcher would use simple geometry to re-establish boundaries after the annual floods of the Nile River; the perfect squareness and north-south orientation of the Great Pyramid of Giza, built c. 2700 BC, affirm the Egyptians' command of surveying. The Groma instrument originated in Mesopotamia; the prehistoric monument at Stonehenge was set out by prehistoric surveyors using peg and rope geometry. The mathematician Liu Hui described ways of measuring distant objects in his work Haidao Suanjing or The Sea Island Mathematical Manual, published in 263 AD; the Romans recognized land surveying as a profession.
They established the basic measurements under which the Roman Empire was divided, such as a tax register of conquered lands. Roman surveyors were known as Gromatici. In medieval Europe, beating the bounds maintained the boundaries of a village or parish; this was the practice of gathering a group of residents and walking around the parish or village to establish a communal memory of the boundaries. Young boys were included to ensure the memory lasted as long as possible. In England, William the Conqueror commissioned the Domesday Book in 1086, it recorded the names of all the land owners, the area of land they owned, the quality of the land, specific information of the area's content and inhabitants. It did not include maps showing exact locations. Abel Foullon described a plane table in 1551, but it is thought that the instrument was in use earlier as his description is of a developed instrument. Gunter's chain was introduced in 1620 by English mathematician Edmund Gunter, it enabled plots of land to be surveyed and plotted for legal and commercial purposes.
Leonard Digges described a Theodolite that measured horizontal angles in his book A geometric practice named Pantometria. Joshua Habermel created a theodolite with a compass and tripod in 1576. Johnathon Sission was the first to incorporate a telescope on a theodolite in 1725. In the 18th century, modern techniques and instruments for surveying began to be used. Jesse Ramsden introduced the first precision theodolite in 1787, it was an instrument for measuring angles in vertical planes. He created his great theodolite using an accurate dividing engine of his own design. Ramsden's theodolite represented a great step forward in the instrument's accuracy. William Gascoigne invented an instrument that used a telescope with an installed crosshair as a target device, in 1640. James Watt developed an optical meter for the measuring of distance in 1771. Dutch mathematician Willebrord Snellius introduced the modern systematic use of triangulation. In 1615 he surveyed the distance from Alkmaar to Breda 72 miles.
He underestimated this distance by 3.5%. The survey was a chain of quadrangles containing 33 triangles in all. Snell showed, he showed how to resection, or calculate, the position of a point inside a triangle using the angles cast between the vertices at the unknown point. These could be measured more than bearings of the vertices, which depended on a compass, his work established the idea of surveying a primary network of control points, locating subsidiary points inside the primary network later. Between 1733 and 1740, Jacques Cassini and his son César undertook the first triangulation of France, they included a re-surveying of the meridian arc, leading to the publication in 1745 of the first map of France constructed on rigorous principles. By this time triangulation methods were well established for local map-making, it was only towards the end of the 18th century that detailed triangulation network surveys mapped whole countries. In 1784, a team from Gene
A pentamirror is an optical device used in the viewfinder systems of various single-lens reflex cameras instead of the pentaprism. It is used to reverse again the laterally reversed image coming from the reflex mirror. Instead of the solid block of glass of the prism in pentaprism system, here 3 mirrors are used to perform the same task; this is cheaper and lighter, but produces a viewfinder image of lower quality and brightness. This optical device is referred to as roof pentamirror because of the roof-like ridge. Pentaprism Single-lens reflex camera Understanding SLR Viewfinders Photo of a Canon 400d pentamirror
Contax began as a camera model in the Zeiss Ikon line in 1932, became a brand name. The early cameras were among the finest in the world featuring high quality Zeiss interchangeable lenses; the final products under the Contax name were a line of 35 mm, medium format, digital cameras engineered and manufactured by Kyocera, featuring modern Zeiss optics. In 2005, Kyocera announced. While the firm of Ernst Leitz of Wetzlar established the 24 mm × 36 mm negative format on perforated 35 mm movie film as a viable photographic system, Zeiss Ikon of Dresden decided to produce a competitor designed to be superior in every way; the name Contax was chosen after a poll among Zeiss employees. Dr. Ing. Heinz Küppenbender was its chief designer. Made between 1932 and 1936, the original Contax, known as Contax I after models were introduced, was markedly different from the corresponding Leica. Using a die-cast alloy body it housed a vertically travelling metal focal-plane shutter reminiscent of the one used in Contessa-Nettel cameras, made out of interlocking blackened brass slats somewhat like a roll-up garage door.
This complex shutter became the characteristic of its Super-Nettel derivative. By contrast, the competitive Leica followed the established design of using rubberized fabric shutter curtains wound around rollers, moving horizontally; the Contax design allowed a higher maximum shutter speed: the top speed was 1/1000s increased to 1/1250s in the Contax II. The fact the shutter ran across the shorter dimension of the format area was a significant factor for achieving this technical feat; the interlocking slats were aligned by specially woven silk ribbons, which were strong but subject to wear. Replacing these ribbons was difficult but, contrary to modern cameras, made for a 400,000-cycle life. Zeiss invented the System Camera, with all sorts of near-photo, wide-angle, mirror-house, long-focal-length lenses for specific situations; however Zeiss called it Universalkamera. One of the key design features was a coupled rangefinder with a long baseline, with its own eyepiece next to that of the viewfinder.
To enhance accuracy, a novel rotating wedge system was employed in lieu of the common swinging mirror mechanism. Other main features included focusing drive built into the camera body for use with standard lens, removable back, shutter-speed knob integral with film-wind knob placed at the front of the camera body, black-enamelled finish; the young lens designer Ludwig Bertele of Ernemann, was charged with the responsibility of designing the lenses. The greatest advantage of the Zeiss lenses was the reduced number of air-to-glass surfaces in Bertele's designs. In the years before lens coating was practiced, this had advantages for contrast and resistance to lens flare. Zeiss pioneered glass coating, before the war coated lenses were offered. After lens coating became universal post WW2, designers were given more freedom in using extra air-to-glass surfaces in correcting lens aberrations, without fear of the ill effects of surface reflections. In 1936 the Contax II and III models were introduced.
They introduced the combined eyepiece for both viewfinder and rangefinder, the shutter speed and film wind knob placed on the top plate, fastest shutter speed at 1/1250 s. and finished in chrome plating. They became popular among professional photographers photojournalists who demanded high-performance, large-aperture lenses for available-light work and a workhorse; the vertical shutter had both variations in speed, slit and a brake at the end of travel, again a Zeiss first. After the Second World War, a few Contax cameras were produced at the original Dresden factory, some were assembled at the Carl Zeiss optical works at Jena, before production was transferred to Kiev in Ukraine. During the war years, the chief designer, Hubert Nerwin, tried to convert the Contax into a single-lens reflex camera but was hindered by the presence of the upper roller of the vertical focal-plane shutter; the postwar design chief Wilhelm Winzenberg started with a clean slate, which became the Contax S though the "S" was not marked on the camera.
The Contax S can be said to be the camera that defined the configuration of the modern 35mm SLR camera. Not only did it introduce the M42 lens mount which became an industry standard, but it was equipped with a horizontal focal-plane shutter, removed a major objection against the reflex camera by offering an unreversed, eye-level viewing image by employing a pentaprism. Introduced in 1949, the S was followed by numerous models including D, E, F, FB, FM and FBM. During that period, VEB Zeiss Ikon, as the firm became known, was under pressure from the new Zeiss Ikon AG in the US zone, so the original Zeiss Ikon and Contax names and trademarks disappeared and were replaced by the new name of Pentacon, which never caught on; this camera line was abandoned. Meanwhile, in the US zone, the three main Zeiss concerns – Carl Zeiss Stiftung, Carl Zeiss optical, Zeiss Ikon – were reestablished. With Hubert Nerwin in charge as design chief, Zeiss Ikon produced revised Contax models, the IIa and IIIa, at a new plant at Stuttgart, they were made until 1962.
With the emergence of the Japanese camera industry a consequence of the US pressure on West Germany's Zeiss to cease collaboration with the East-German Zeiss, the lack of raw materials the former was enduring, it was in a way forced to form an alliance with a Japanese maker. Asahi, maker of the Pentax, was engaged first
A retroreflector is a device or surface that reflects radiation back to its source with a minimum of scattering. In a retroreflector the wavefront of the radiation is reflected straight back to the wave's source; this works at a wide range of angle of incidence, unlike a planar mirror, which does this only if the mirror is perpendicular to the wave front, having a zero angle of incidence. Being directed, the retroflector's reflection is brighter than that of a diffuse reflector. Corner reflectors and cat eye reflectors are the most used kinds. There are several ways to obtain retroreflection: A set of three mutually perpendicular reflective surfaces, placed to form the corner of a cube, work as a retroreflector; the three corresponding normal vectors of the corner's sides form a basis in which to represent the direction of an arbitrary incoming ray. When the ray reflects from the first side, say x, the ray's x-component, a, is reversed to −a, while the y- and z-components are unchanged. Therefore, as the ray reflects first from side x side y and from side z the ray direction goes from to to to and it leaves the corner with all three components of its direction reversed.
Corner reflectors occur in two varieties. In the more common form, the corner is the truncated corner of a cube of transparent material such as conventional optical glass. In this structure, the reflection is achieved either by total internal reflection or silvering of the outer cube surfaces; the second form uses mutually perpendicular flat mirrors bracketing an air space. These two types have similar optical properties. A large thin retroreflector can be formed by combining many small corner reflectors, using the standard hexagonal tiling. Another common type of retroreflector consists of refracting optical elements with a reflective surface, arranged so that the focal surface of the refractive element coincides with the reflective surface a transparent sphere and a spherical mirror. In the paraxial approximation, this effect can be achieved with lowest divergence with a single transparent sphere when the refractive index of the material is one plus the refractive index ni of the medium from which the radiation is incident.
In that case, the sphere surface behaves as a concave spherical mirror with the required curvature for retroreflection. In practice, the optimal index of refraction may be lower than ni + 1 ≅ 2 due to several factors. For one, it is sometimes preferable to have an imperfect divergent retroreflection, as in the case of road signs, where the illumination and observation angles are different. Due to spherical aberration, there exists a radius from the centerline at which incident rays are focused at the center of the rear surface of the sphere. High index materials have higher Fresnel reflection coefficients, so the efficiency of coupling of the light from the ambient into the sphere decreases as the index becomes higher. Commercial retroreflective beads thus vary in index from around 1.5 up to around 1.9. The spherical aberration problem with the spherical cat's eye can be solved in various ways, one being a spherically symmetrical index gradient within the sphere, such as in the Luneburg lens design.
This can be approximated by a concentric sphere system. Because the back-side reflection for an uncoated sphere is imperfect, it is common to add a metallic coating to the back half of retroreflective spheres to increase the reflectance, but this implies that the retroreflection only works when the sphere is oriented in a particular direction. An alternative form of the cat's eye retroreflector uses a normal lens focused onto a curved mirror rather than a transparent sphere, though this type is much more limited in the range of incident angles that it retroreflects; the term cat's eye derives from the resemblance of the cat's eye retroreflector to the optical system that produces the well-known phenomenon of "glowing eyes" or eyeshine in cats and other vertebrates. The combination of the eye's lens and the cornea form the refractive converging system, while the tapetum lucidum behind the retina forms the spherical concave mirror; because the function of the eye is to form an image on the retina, an eye focused on a distant object has a focal surface that follows the reflective tapetum lucidum structure, the condition required to form a good retroreflection.
This type of retroreflector can consist of many small versions of these structures incorporated in a thin sheet or in paint. In the case of paint containing glass beads, the paint adheres the beads to the surface where retroreflection is required and the beads protrude, their diameter being about twice the thickness of the paint. A third, much less common way of producing a retroreflector is to use the nonlinear optical phenomenon of phase conjugation; this technique is used in advanced optical systems such as high-power lasers and optical transmission lines. Phase-conjugate mirrors require a comparatively expensive and complex apparatus, as well as large quantities of power. However, phase-conjugate mirrors have an inherently much greater accuracy in the direction of the retroreflection, which in passive elements is limited by the mechanical accuracy of the construction. Retroreflectors are devices that operate by returning light back to the light source along the same light direction; the coefficient of luminous intensity, RI, is the measure of a r
In optics, a prism is a transparent optical element with flat, polished surfaces that refract light. At least two of the flat surfaces must have an angle between them; the exact angles between the surfaces depend on the application. The traditional geometrical shape is that of a triangular prism with a triangular base and rectangular sides, in colloquial use "prism" refers to this type; some types of optical prism are not in fact in the shape of geometric prisms. Prisms can be made from any material, transparent to the wavelengths for which they are designed. Typical materials include glass and fluorite. A dispersive prism can be used to break light up into its constituent spectral colors. Furthermore, prisms can be used to reflect light, or to split light into components with different polarizations. Light changes speed; this speed change causes the light to enter the new medium at a different angle. The degree of bending of the light's path depends on the angle that the incident beam of light makes with the surface, on the ratio between the refractive indices of the two media.
The refractive index of many materials varies with the wavelength or color of the light used, a phenomenon known as dispersion. This causes light of different colors to be refracted differently and to leave the prism at different angles, creating an effect similar to a rainbow; this can be used to separate a beam of white light into its constituent spectrum of colors. A similar separation happens with iridescent materials, such as a soap bubble. Prisms will disperse light over a much larger frequency bandwidth than diffraction gratings, making them useful for broad-spectrum spectroscopy. Furthermore, prisms do not suffer from complications arising from overlapping spectral orders, which all gratings have. Prisms are sometimes used for the internal reflection at the surfaces rather than for dispersion. If light inside the prism hits one of the surfaces at a sufficiently steep angle, total internal reflection occurs and all of the light is reflected; this makes a prism a useful substitute for a mirror in some situations.
Ray angle deviation and dispersion through a prism can be determined by tracing a sample ray through the element and using Snell's law at each interface. For the prism shown at right, the indicated angles are given by θ 0 ′ = arcsin θ 1 = α − θ 0 ′ θ 1 ′ = arcsin θ 2 = θ 1 ′ − α. All angles are positive in the direction shown in the image. For a prism in air n 0 = n 2 ≃ 1. Defining n = n 1, the deviation angle δ is given by δ = θ 0 + θ 2 = θ 0 + arcsin − α If the angle of incidence θ 0 and prism apex angle α are both small, sin θ ≈ θ and arcsin x ≈ x if the angles are expressed in radians; this allows the nonlinear equation in the deviation angle δ to be approximated by δ ≈ θ 0 − α + = θ 0 − α + n α − θ 0 = α
A camera is an optical instrument to capture still images or to record moving images, which are stored in a physical medium such as in a digital system or on photographic film. A camera consists of a lens which focuses light from the scene, a camera body which holds the image capture mechanism; the still image camera is the main instrument in the art of photography and captured images may be reproduced as a part of the process of photography, digital imaging, photographic printing. The similar artistic fields in the moving image camera domain are film and cinematography; the word camera comes from camera obscura, which means "dark chamber" and is the Latin name of the original device for projecting an image of external reality onto a flat surface. The modern photographic camera evolved from the camera obscura; the functioning of the camera is similar to the functioning of the human eye. The first permanent photograph was made in 1825 by Joseph Nicéphore Niépce. A camera works with the light of the visible spectrum or with other portions of the electromagnetic spectrum.
A still camera is an optical device which creates a single image of an object or scene and records it on an electronic sensor or photographic film. All cameras use the same basic design: light enters an enclosed box through a converging/convex lens and an image is recorded on a light-sensitive medium. A shutter mechanism controls the length of time. Most photographic cameras have functions that allow a person to view the scene to be recorded, allow for a desired part of the scene to be in focus, to control the exposure so that it is not too bright or too dim. On most digital cameras a display a liquid crystal display, permits the user to view the scene to be recorded and settings such as ISO speed and shutter speed. A movie camera or a video camera operates to a still camera, except it records a series of static images in rapid succession at a rate of 24 frames per second; when the images are combined and displayed in order, the illusion of motion is achieved. Traditional cameras capture light onto photographic film.
Video and digital cameras use an electronic image sensor a charge coupled device or a CMOS sensor to capture images which can be transferred or stored in a memory card or other storage inside the camera for playback or processing. Cameras that capture many images in sequence are known as movie cameras or as ciné cameras in Europe; however these categories overlap as still cameras are used to capture moving images in special effects work and many modern cameras can switch between still and motion recording modes. A wide range of film and plate formats have been used by cameras. In the early history plate sizes were specific for the make and model of camera although there developed some standardisation for the more popular cameras; the introduction of roll film drove the standardization process still further so that by the 1950s only a few standard roll films were in use. These included 120 film providing 8, 12 or 16 exposures, 220 film providing 16 or 24 exposures, 127 film providing 8 or 12 exposures and 135 providing 12, 20 or 36 exposures – or up to 72 exposures in the half-frame format or in bulk cassettes for the Leica Camera range.
For cine cameras, film 35 mm wide and perforated with sprocket holes was established as the standard format in the 1890s. It was used for nearly all film-based professional motion picture production. For amateur use, several smaller and therefore less expensive formats were introduced. 17.5 mm film, created by splitting 35 mm film, was one early amateur format, but 9.5 mm film, introduced in Europe in 1922, 16 mm film, introduced in the US in 1923, soon became the standards for "home movies" in their respective hemispheres. In 1932, the more economical 8 mm format was created by doubling the number of perforations in 16 mm film splitting it after exposure and processing; the Super 8 format, still 8 mm wide but with smaller perforations to make room for larger film frames, was introduced in 1965. Traditionally used to "tell the camera" the film speed of the selected film on film cameras, film speed numbers are employed on modern digital cameras as an indication of the system's gain from light to numerical output and to control the automatic exposure system.
Film speed is measured via the ISO system. The higher the film speed number the greater the film sensitivity to light, whereas with a lower number, the film is less sensitive to light. On digital cameras, electronic compensation for the color temperature associated with a given set of lighting conditions, ensuring that white light is registered as such on the imaging chip and therefore that the colors in the frame will appear natural. On mechanical, film-based cameras, this function is served by the operator's choice of film stock or with color correction filters. In addition to using white balance to register natural coloration of the image, photographers may employ white balance to aesthetic end, for example, white balancing to a blue object in order to obtain a warm color temperature; the lens of a camera brings it to a focus on the sensor. The design and manufacture of the lens is critical to the quality of the photograph being taken; the technological revolution in camera design in the 19th century revolutionized optical glass manufacture and lens design with great benefits for modern lens manufacture in a wide range of optical instruments from reading glasses to microscopes.
Pioneers included Leitz. Camera lenses are
A plumb bob, or plummet, is a weight with a pointed tip on the bottom, suspended from a string and used as a vertical reference line, or plumb-line. It is the vertical equivalent of a "water level"; the instrument has been used since at least the time of ancient Egypt to ensure that constructions are "plumb", or vertical. It is used in surveying, to establish the nadir with respect to gravity of a point in space, it is used with a variety of instruments to set the instrument over a fixed survey marker or to transcribe positions onto the ground for placing a marker. The "plumb" in "plumb-bob" comes from the fact that such tools were made of lead; the adjective "plumb" developed by extension, as did the noun "aplomb," from the notion of "standing upright." Until the modern age, plumb-bobs were used on most tall structures to provide vertical datum lines for the building measurements. A section of the scaffolding would hold a plumb line, centered over a datum mark on the floor; as the building proceeded upward, the plumb line would be taken higher, still centered on the datum.
Many cathedral spires and towers still have brass datum marks inlaid into their floors, which signify the center of the structure above. Although a plumb-bob and line alone can determine only a vertical if they are mounted on a suitable scale, the instrument may be used as an inclinometer to measure angles to the vertical; the early skyscrapers used heavy plumb-bobs, hung on wire in their elevator shafts. A plumb bob may be in a container of water, molasses viscous oils or other liquids to dampen any swinging movement, functioning as a shock absorber. Students of figure drawing will make use of a plumb line to find the vertical axis through the center of gravity of their subject and lay it down on paper as a point of reference; the device used may be purpose-made plumb lines, or makeshift devices made from a piece of string and a weighted object, such as a metal washer. This plumb line is important for lining up anatomical geometries and visualizing the subject's center of balance. Bob Centre of mass – used to find the centre of mass on a 2D shape which has uniform density Chalk line Gravity direction Vertical direction 60 oz. Plumb Bob.
String Line and Plumb Bob