Geodesy Wikipedia. Geodesy ,1 also known as geodetics, geodetic engineering or geodetics engineering a branch of applied mathematics2 and earth sciences, is the scientific discipline that deals with the measurement and representation of the Earth or any planet, including its gravitational field, in a three dimensional time varying space. Geodesists also study geodynamical phenomena such as crustal motion, tides, and polar motion. For this they design global and national control networks, using space and terrestrial techniques while relying on datums and coordinate systems. DefinitioneditGeodesy from the Ancient Greek word geodaisia literally, division of the Earth is primarily concerned with positioning within the temporally varying gravity field. Geodesy in the German speaking world is divided into higher geodesy Erdmessung or hhere Geodsie, which is concerned with measuring the Earth on the global scale, and practical geodesy or engineering geodesy Ingenieurgeodsie, which is concerned with measuring specific parts or regions of the Earth, and which includes surveying. Such geodetic operations are also applied to other astronomical bodies in the solar system. It is also the science of measuring and understanding the earths geometric shape, orientation in space, and gravity field. The shape of the Earth is to a large extent the result of its rotation, which causes its equatorial bulge, and the competition of geological processes such as the collision of plates and of volcanism, resisted by the Earths gravity field. This applies to the solid surface, the liquid surface dynamic sea surface topography and the Earths atmosphere. For this reason, the study of the Earths gravity field is called physical geodesy by some. HistoryeditGeoid and reference ellipsoideditThe geoid is essentially the figure of the Earth abstracted from its topographical features. It is an idealized equilibrium surface of sea water, the mean sea level surface in the absence of currents, air pressure variations etc. The geoid, unlike the reference ellipsoid, is irregular and too complicated to serve as the computational surface on which to solve geometrical problems like point positioning. The geometrical separation between the geoid and the reference ellipsoid is called the geoidal undulation. It varies globally between 1. GRS 8. 0 ellipsoid. A reference ellipsoid, customarily chosen to be the same size volume as the geoid, is described by its semi major axis equatorial radius a and flattening f. The quantity f  a ba, where b is the semi minor axis polar radius, is a purely geometrical one. The mechanical ellipticity of the Earth dynamical flattening, symbol J2 can be determined to high precision by observation of satellite orbit perturbations. Its relationship with the geometrical flattening is indirect. The relationship depends on the internal density distribution, or, in simplest terms, the degree of central concentration of mass. This is a list of geocoding systems, in the sense of schemes that assign systematic labels to geographic entities. This is not a list of software systems that can. Mehaffey, Yeazel and DePriests site provides dozens of reviews and technical articles on GPS receivers and software, and a huge list of links. The 1. 98. 0 Geodetic Reference System GRS 8. This system was adopted at the XVII General Assembly of the International Union of Geodesy and Geophysics IUGG. It is essentially the basis for geodetic positioning by the Global Positioning System and is thus also in widespread use outside the geodetic community. EasyGPS free GPS software for your Garmin nvi 1300 GPS receiver. Garmin nuvi 1300, Garmin nvi 1300, nuvi1300. Project Management White Paper Index. The Project Perfect White Paper Collection has been put together from our own resources, and some of our customers. Datasets in the Global Wind Atlas. The data used in the Global Wind Atlas was chosen from the best availible global datasets for each required category. Driver San Francisco 3D Models there. Rmx0yRBxyvBJVDJFeX3wmre_nrQ5iHiniVViqi_SCaMcICuolgYtjPlmXPjoxGfC3I' alt='Mgrs Mapping Software' title='Mgrs Mapping Software' />The numerous other systems which have been used by diverse countries for their maps and charts are gradually dropping out of use as more and more countries move to global, geocentric reference systems using the GRS 8. It should be noted that the geoid is realizable, i. Earth by suitable simple measurements from physical objects, e. It can therefore be considered a real surface. The reference ellipsoid, by contrast, has many possible instantiations and is not readily realizable, so is an abstract surface. The third primary surface of geodetic interest, the surface of the Earth itself, is a realizable surface. Coordinate systems in spaceeditThe locations of points in three dimensional space are most conveniently described by three cartesian or rectangular coordinates, X, Y and Z. Since the advent of satellite positioning, such coordinate systems are typically geocentric the Z axis is aligned with the Earths conventional or instantaneous rotation axis. Prior to the era of satellite geodesy, the coordinate systems associated with a geodetic datum attempted to be geocentric, but their origins differed from the geocentre by hundreds of metres, due to regional deviations in the direction of the plumbline vertical. These regional geodetic data, such as ED 5. European Datum 1. NAD 2. 7 North American Datum 1. It is only because GPS satellites orbit about the geocentre, that this point becomes naturally the origin of a coordinate system defined by satellite geodetic means, as the satellite positions in space are themselves computed in such a system. Geocentric coordinate systems used in geodesy can be divided naturally into two classes Inertial reference systems, where the coordinate axes retain their orientation relative to the fixed stars, or equivalently, to the rotation axes of ideal gyroscopes the X axis points to the vernal equinox. Co rotating, also ECEF Earth Centred, Earth Fixed, where the axes are attached to the solid body of the Earth. The X axis lies within the Greenwich observatorys meridian plane. The coordinate transformation between these two systems is described to good approximation by apparent sidereal time, which takes into account variations in the Earths axial rotation length of day variations. A more accurate description also takes polar motion into account, a phenomenon closely monitored by geodesists. Coordinate systems in the planeeditIn surveying and mapping, important fields of application of geodesy, two general types of coordinate systems are used in the plane Plano polar, in which points in a plane are defined by a distance s from a specified point along a ray having a specified direction with respect to a base line or axis Rectangular, points are defined by distances from two perpendicular axes called x and y. It is geodetic practicecontrary to the mathematical conventionto let the x axis point to the north and the y axis to the east. Rectangular coordinates in the plane can be used intuitively with respect to ones current location, in which case the x axis will point to the local north. More formally, such coordinates can be obtained from three dimensional coordinates using the artifice of a map projection. It is not possible to map the curved surface of the Earth onto a flat map surface without deformation. The compromise most often chosencalled a conformal projectionpreserves angles and length ratios, so that small circles are mapped as small circles and small squares as squares. An example of such a projection is UTM Universal Transverse Mercator. Within the map plane, we have rectangular coordinates x and y. Php Project Script. In this case the north direction used for reference is the map north, not the local north. The difference between the two is called meridian convergence. It is easy enough to translate between polar and rectangular coordinates in the plane let, as above, direction and distance be and s respectively, then we havexscosyssindisplaystyle beginalignedx scos alpha y ssin alpha endalignedThe reverse transformation is given by sx.