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Georeferenced
Georeferencing or georegistration is a type of coordinate transformation that binds a digital raster image or vector database that represents a geographic space (usually a scanned map or aerial photograph) to a spatial reference system, thus locating the digital data in the real world. It is thus the geographic form of image registration or image rectification. The term can refer to the mathematical formulas used to perform the transformation, the metadata stored alongside or within the image file to specify the transformation, or the process of manually or automatically aligning the image to the real world to create such metadata. The most common result is that the image can be visually and analytically integrated with other geographic data in geographic information systems and remote sensing software. A number of mathematical methods are available, but the process typically involves identifying a sample of several ground control points (GCPs) with known locations on the image ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orthophoto
An orthophoto, orthophotograph, orthoimage or orthoimagery is an Aerial photography, aerial photograph or satellite imagery geometrically corrected ("orthorectified") such that the scale is uniform: the photo or image follows a given map projection. Unlike an uncorrected aerial photograph, an orthophoto can be used to measure true distances, because it is an accurate representation of the Earth's surface, having been adjusted for Topography, topographic relief, Barrel distortion, lens distortion, and camera tilt. Orthophotographs are commonly used in geographic information systems (GIS) as a "map accurate" background image. An orthorectified image differs from "rubber sheeted" rectifications as the latter may accurately locate a number of points on each image but "stretch" the area between so scale may not be uniform across the image. A Digital elevation model, digital elevation model (DEM) is required to create an accurate orthophoto as distortions in the image due to th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Remote Sensing
Remote sensing is the acquisition of information about an physical object, object or phenomenon without making physical contact with the object, in contrast to in situ or on-site observation. The term is applied especially to acquiring information about Earth and other planets. Remote sensing is used in numerous fields, including geophysics, geography, land surveying and most Earth science disciplines (e.g. exploration geophysics, hydrology, ecology, meteorology, oceanography, glaciology, geology). It also has military, intelligence, commercial, economic, planning, and humanitarian applications, among others. In current usage, the term ''remote sensing'' generally refers to the use of satellite- or airborne-based sensor technologies to detect and classify objects on Earth. It includes the surface and the atmosphere and oceans, based on wave propagation, propagated signals (e.g. electromagnetic radiation). It may be split into "active" remote sensing (when a signal is emitted b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data Model (GIS)
A geographic data model, geospatial geographical measurements, or simply data from modules in the context of geographic information systems (GIS), is a mathematical and digital structure for representing phenomena over the Earth. Generally, such data modules represent various aspects of these phenomena by means of statistical data measurement, including locations, change over time. For example, the vector graphic data model represents geography as collections of points, lines, and arrays, and the elimination data model represent geography as space matrices that store numeric values. Data models are implemented throughout the GIS ecosystem, including the software tools for data management and spatial analysis, data stored in very specific languages of GIS file formats specifications and standards, and specific designs for GIS installations. While the unique nature of spatial information has led to its own set of model structures, much of the process of data modeling is similar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coordinate Transformation
In geometry, a coordinate system is a system that uses one or more numbers, or coordinates, to uniquely determine and standardize the position of the points or other geometric elements on a manifold such as Euclidean space. The coordinates are not interchangeable; they are commonly distinguished by their position in an ordered tuple, or by a label, such as in "the ''x''-coordinate". The coordinates are taken to be real numbers in elementary mathematics, but may be complex numbers or elements of a more abstract system such as a commutative ring. The use of a coordinate system allows problems in geometry to be translated into problems about numbers and ''vice versa''; this is the basis of analytic geometry. Common coordinate systems Number line The simplest example of a coordinate system is the identification of points on a line with real numbers using the ''number line''. In this system, an arbitrary point ''O'' (the ''origin'') is chosen on a given line. The coordinate of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rubbersheeting
In cartography and geographic information systems, rubbersheeting is a form of coordinate transformation that warps a vector dataset to match a known geographic space. This is most commonly needed when a dataset has systematic positional error, such as one digitized from a historical map of low accuracy. The mathematics and procedure are very similar to the georeferencing of raster images, and this term is occasionally used for that process as well, but ''image georegistration'' is an unambiguous term for the raster process. Applications in history and historical geography Rubbersheeting is a useful technique in HGIS, where it is used to digitize and add old maps as feature layers in a modern GIS. Before aerial photography arrived, most maps were highly inaccurate by modern standards. Rubbersheeting may improve the value of such sources and make them easier to compare to modern maps. Software * ESRI's ArcGIS 8.3+ has the capability of rubbersheeting vector data, and Ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geographic Information System
A geographic information system (GIS) consists of integrated computer hardware and Geographic information system software, software that store, manage, Spatial analysis, analyze, edit, output, and Cartographic design, visualize Geographic data and information, geographic data. Much of this often happens within a spatial database; however, this is not essential to meet the definition of a GIS. In a broader sense, one may consider such a system also to include human users and support staff, procedures and workflows, the Geographic Information Science and Technology Body of Knowledge, body of knowledge of relevant concepts and methods, and institutional organizations. The uncounted plural, ''geographic information systems'', also abbreviated GIS, is the most common term for the industry and profession concerned with these systems. The academic discipline that studies these systems and their underlying geographic principles, may also be abbreviated as GIS, but the unambiguous GIScie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thin Plate Spline
Thin plate splines (TPS) are a spline-based technique for data interpolation and smoothing. They were introduced to geometric design by Duchon. They are an important special case of a polyharmonic spline. Robust Point Matching (RPM) is a common extension and shortly known as the TPS-RPM algorithm. Physical analogy The name ''thin plate spline'' refers to a physical analogy involving the bending of a plate or thin sheet of metal. Just as the metal has rigidity, the TPS fit resists bending also, implying a penalty involving the smoothness of the fitted surface. In the physical setting, the deflection is in the z direction, orthogonal to the plane. In order to apply this idea to the problem of coordinate transformation, one interprets the lifting of the plate as a displacement of the x or y coordinates within the plane. In 2D cases, given a set of K corresponding control points (knots), the TPS warp is described by 2(K+3) parameters which include 6 global affine motion parameters a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Distortion (optics)
In geometric optics, distortion is a deviation from rectilinear projection; a projection in which straight lines in a scene remain straight in an image. It is a form of optical aberration that may be distinguished from other aberrations such as spherical aberration, coma, chromatic aberration, field curvature, and astigmatism in a sense that these impact the image sharpness without changing an object shape or structure in the image (e.g., a straight line in an object is still a straight line in the image although the image sharpness may be degraded by the mentioned aberrations) while distortion can change the object structure in the image (so named as distortion). Radial distortion Although distortion can be irregular or follow many patterns, the most commonly encountered distortions are radially symmetric, or approximately so, arising from the symmetry of a photographic lens. These ''radial distortions'' can usually be classified as either ''barrel'' distortions or ' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
World File
A world file is a six line plain text sidecar file used by geographic information systems (GIS) to georeference raster map images. The file specification was introduced by Esri. Filename extension The base filename of a world file matches the raster's base filename, but has a different filename extension (suffix). There are three filename extension naming conventions used for world files, with variable support across software. One simple convention with widespread support is to append the letter "w" to the end of the raster filename. For example, a raster named should have a world file named . An alternative file naming convention that uses a three-character extension to conform to the 8.3 file naming convention uses the first and last character of the raster file's extension, followed by "w" at the end. For example, here are a few naming conventions for popular raster formats: A third convention is to use a file extension, irrespective of the type of raster file, as suppo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spatial Resolution
In physics and geosciences, the term spatial resolution refers to distance between independent measurements, or the physical dimension that represents a pixel of the image. While in some instruments, like cameras and telescopes, spatial resolution is directly connected to angular resolution, other instruments, like synthetic aperture radar or a network of weather stations, produce data whose spatial sampling layout is more related to the Earth's surface, such as in remote sensing and satellite imagery. See also * Image resolution Image resolution is the level of detail of an image. The term applies to digital images, film images, and other types of images. "Higher resolution" means more image detail. Image resolution can be measured in various ways. Resolution quantifies ... * Ground sample distance * Level of detail * Resel References Accuracy and precision {{physics-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Affine Transformation
In Euclidean geometry, an affine transformation or affinity (from the Latin, '' affinis'', "connected with") is a geometric transformation that preserves lines and parallelism, but not necessarily Euclidean distances and angles. More generally, an affine transformation is an automorphism of an affine space (Euclidean spaces are specific affine spaces), that is, a function which maps an affine space onto itself while preserving both the dimension of any affine subspaces (meaning that it sends points to points, lines to lines, planes to planes, and so on) and the ratios of the lengths of parallel line segments. Consequently, sets of parallel affine subspaces remain parallel after an affine transformation. An affine transformation does not necessarily preserve angles between lines or distances between points, though it does preserve ratios of distances between points lying on a straight line. If is the point set of an affine space, then every affine transformation on can ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Universal Transverse Mercator
The Universal Transverse Mercator (UTM) is a map projection system for assigning coordinates to locations on the surface of the Earth. Like the traditional method of latitude and longitude, it is a horizontal position representation, which means it ignores altitude and treats the earth surface as a perfect ellipsoid. However, it differs from global latitude/longitude in that it divides earth into 60 zones and projects each to the plane as a basis for its coordinates. Specifying a location means specifying the zone and the ''x'', ''y'' coordinate in that plane. The projection from spheroid to a UTM zone is some parameterization of the transverse Mercator projection. The parameters vary by nation or region or mapping system. Most zones in UTM span 6 degrees of longitude, and each has a designated central meridian. The scale factor at the central meridian is specified to be 0.9996 of true scale for most UTM systems in use. History The National Oceanic and Atmospheric Administratio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
