Construction surveying
Construction surveying or building surveying (otherwise known as "staking", "stake-out", "lay-out", "setting-out" or "BS") is to stake out reference points and markers that will guide the construction of new structures such as roads or buildings. These markers are usually staked out according to a suitable coordinate system selected for the project. Coordinate systems used in construction. Land surveys and surveys of existing conditions are generally performed according to geodesic coordinates. However, for the purposes of construction a more suitable coordinate system will often be used. During construction surveying, the surveyor will often have to convert  from geodesic coordinates to the coordinate system used for that project. Chainage or station. In the case of roads or other linear infrastructure, a "chainage" (derived from Gunter's Chain - 1 chain is equal to 66 feet or 100 links) will be established, often to correspond with the centre line of the road or pipeline. During construction, structures would then be located in terms of "chainage", "offset" and "elevation". "Offset" is said to be "left" or "right" relative to someone standing on the "chainage line" who is looking in the direction of increasing "chainage". Plans would often show "plan" views  (viewed from above), "profile" views (a "transparent" section view collapsing all section views of the road parallel to the "chainage") or "cross-section" views (a "true" section view perpendicular to the "chainage"). In a "plan" view, "chainage" generally increases from left to right, or from the bottom to the top of the plan. "Profiles" are shown with the chainage increasing from left to right, and "cross-sections" are shown as if the viewer is looking in the direction of increasing "chainage" (so that the "left" "offset" is to the "left" and the "right" "offset" is to the "right"). "Chainage" may  also be referred to as "Station". Building grids. In the case of buildings, an arbitrary system of grids is often established so as to correspond to the rows of columns and the major load-bearing walls of the building. The grids may be identified alphabetically in one direction, and numerically in the other direction (as in a road map). The grids are usually but not necessarily perpendicular, and are often but not necessarily evenly spaced. Floors and basement levels are also numbered. Structures, equipment or architectural details may be located in reference to the floor and the nearest intersection of  the arbitrary axes. Other coordinate systems. In other types of construction projects, arbitrary "plan north" reference lines may be established, using Cartesian coordinates that may or may not necessarily correspond to true coordinates. The technique is called localized grid. This method uses the plan building grids as their own ordinates. A point of beginning is established at the southwest cross grid. IE [N1000.000,E3000.000] The grids are added together heading north and east to make each line its own ordinate. Equipment and techniques used in construction surveying. Surveying equipment, such as levels and theodolites, are used for accurate measurement of angular  deviation, horizontal, vertical and slope distances. With computerisation, electronic distance measurement (EDM), total stations, GPS surveying and laser scanning have supplemented (and to a large extent supplanted) the traditional optical instruments. The builder's level measures neither horizontal nor vertical angles. It simply combines a spirit level and telescope to allow the user to visually establish a line of sight along a level plane. When used together with a graduated staff it can be used to transfer elevations from one location to another. An alternative method to transfer elevation is to use water in a transparent hose as the level  of the water in the hose at opposite ends will be at the same elevation. A double right angle prism verifies grid patterns, isolating layout errors. Equipment and techniques used in mining and tunneling. Total stations are the primary survey instrument used in mining surveying. Underground mining. A total station is used to record the absolute location of the tunnel walls' (stopes), ceilings (backs), and floors as the drifts of an underground mine are driven. The recorded data is then downloaded into a CAD programme, and compared to the designed layout of the tunnel. The survey party installs control stations  at regular intervals. These are small steel plugs installed in pairs in holes drilled into walls or the back. For wall stations, two plugs are installed in opposite walls, forming a line perpendicular to the drift. For back stations, two plugs are installed in the back, forming a line parallel to the drift. A set of plugs can be used to locate the total station set up in a drift or tunnel by processing measurements to the plugs by intersection and resection. Profession. Building Surveying emerged in the 1970s as a profession in the United Kingdom by a group of  technically minded General Practice Surveyors. Building Surveying is a recognized profession within Britain and Australia. In Australia in particular, due to risk mitigation/limitation factors the employment of surveyors at all levels of the construction industry is widespread. There are still many countries where it is not widely recognized as a profession. The Services that Building Surveyors undertake are broad but include: Building Surveyors also advise on many aspects of construction including: Clients of a building surveyor can be the public sector, Local Authorities, Government Departments as well as private sector organisations and work closely with architects, planners, homeowners and  tenants groups. Building Surveyors may also be called to act as an expert witness. It is usual for building surveyors to undertake an accredited degree qualification before undertaking structured training to become a member of a professional organisation. For Chartered Building Surveyors, these courses are accredited by the Royal Institution of Chartered Surveyors. Other professional organisations that have building surveyor members include CIOB, ABE, HKIS and RICS. With the enlargement of the European community, the profession of the Chartered Building Surveyor is becoming more widely known in other European states, particularly France. Chartered Building Surveyors, where many English speaking people  buy second homes. Distinction from land surveyors. In the United States, Canada, the United Kingdom and most Commonwealth countries land surveying is considered to be a distinct profession. Land surveyors have their own professional associations and licensing requirements. The services of a licensed land surveyor are generally required for boundary (also known as cadastral) surveys for