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Location Awareness and Navigation in Location-Based Systems
Published in Krzysztof W. Kolodziej, Johan Hjelm, Local Positioning Systems, 2017
Krzysztof W. Kolodziej, Johan Hjelm
Absolute positioning is when objects have specific (x, y, z) coordinates (globally expressed in latitude, longitude, and altitude) or are positioned as a metric offset from a fixed reference. There is a spatial reference unique to each specific position. Absolute information provides three-dimensional position coordinates in standard format relative to the Earth, using WGS84 as the reference system (Department of Defense, 2000). Latitude and longitude are defined with respect to the WGS84 ellipsoid representation of the Earth. Altitude or elevation is defined as the distance above the ellipsoid (representing the surface of the Earth). Furthermore, an absolute position allows the determination of positioning information of disjunct systems independently, in reference to the same point in the inertial system. Also, dynamic navigation systems can surpass this problem partially by adding motion in form of a history of past positions or velocities to the problem’s solution.
Active Microwaves
Published in Iain H. Woodhouse, Introduction to Microwave Remote Sensing, 2006
The geoid is not always the best reference surface, however — what is “mean sea level” to someone living in Switzerland? The geoid is also difficult to use for mapping purposes since it is a real property that must be measured, rather than being a mathematically well-defined reference surface. The latter are referred to as ellipsoids, which are created to provide a common reference surface in order to define vertical location and to form the basis of map projections. In Chapter 10 we will discuss the need for some reference surface onto which we can project our radar image. WGS84 (the World Geodetic System defined in 1984) in one such global ellipsoid that is commonly used in planetary-scale studies and Earth observation. Ellipsoids
The definition of time and different time systems
Published in Lucien Wald, Fundamentals of Solar Radiation, 2021
Geographic coordinates Φ and λ are associated with a geodetic system, which is a mathematical expression aimed at getting as close as possible to the gravity field of the Earth. The most widely used geodetic system in the world today is the World Geodetic System 84 (WGS84). It is the basis of the Global Positioning System (GPS) frequently used to know the geographic coordinates of a place. This geodetic system differs from the sphere since it takes into account in particular the flattening at the poles. This is why the geocentric and geographic coordinates differ. The difference must be accounted for when calculating the angles defining the position of the sun relative to a ground observer.
NDT spatial data integration for monumental buildings: technical information management for the Royal Alcazar of Seville
Published in Building Research & Information, 2023
Francisco M. Hidalgo-Sánchez, Marta Torres-González, Emilio J. Mascort-Albea, Jacinto Canivell, Rocío Romero-Hernández, J. J. Martín-del-Río
The 2D features corresponding to each ULA have been drawn manually using the computer-aided design software AutoCAD Map 3D v.2021. These 2D polylines have been drawn on the geo-referenced base planimetry of the RAS previously created by the authors, thereby guaranteeing their correct geographical location. The WGS84 geographic projection system is used. These 2D features of each ULA were exported to shapefile files with polygonal geometry and imported into ArcGIS Pro v.2.9 software as independent layers. In order to facilitate their management, all 2D geometry layers are converted into feature classes of a single geodatabase. Finally, each feature is assigned its corresponding identification code (Figure 9). Figure 8 includes a quantification of the number of 2D features that have been modelled.
A novel context-aware system to improve driver’s field of view in urban traffic networks
Published in Journal of Intelligent Transportation Systems, 2022
A. Nourbakhshrezaei, M. Jadidi, M. R. Delavar, B. Moshiri
where represents the vehicle movement. In order to prevent additional processing on the main server, the mentioned condition is checked on the client’s application. GPS positions are recorded as Latitude and Longitude with respect to the WGS84 reference ellipsoid. As the smartphone application is used to find the location of the vehicles, the accuracy of the positioning is related to the quality of the GPS antenna embedded in the smartphones. The mean accuracy in an urban environment is about 3 meters under good condition (Dabove & Di Pietra, 2019). However, there is a strong correlation between the accuracy and building’s height. The height of buildings can affect accuracy in two ways: a) Satellite signal blockage (Tirkas et al., 1998) and b) Signal reflection (multi-path) (Byun et al., 2002). These two errors decrease accuracy to up to 15 meters in some places. The accuracy is acceptable since the purpose of using GPS data in this research is to calculate the relative distance between camera’s location (east, west, north, south) and the vehicles near to RSU. To classify vehicles regarding their distances from the RSUs, ellipsoid curvilinear positions should be projected to the plane using UTM projection system.
Error analysis of exterior orientation elements on geolocation for a Moon-based Earth observation optical sensor
Published in International Journal of Digital Earth, 2020
Huadong Guo, Hanlin Ye, Guang Liu, Changyong Dou, Jing Huang
This model includes the geometric relationship and the image model. The geometric relationship is the foundation of this model and the latter describes the one-to-one mapping process between the Earth surface feature and the image, considering the sensor’s position on the lunar surface and the precise Earth–Moon geometric relationship. We have proposed the transformation process in the previous study (Liu et al. 2016; Ren et al. 2017; Ye et al. 2017). Eight coordinate systems are defined and the transformations of different coordinate systems are given. The diagram of the transformation process is shown in Figure 1. The position of the Earth surface feature is expressed as the latitude, longitude, and altitude defined in WGS84. Through a series of coordinate system transformations, the position of the Earth surface feature is finally defined in the sensor body-fixed coordinate system. The sensor body-fixed coordinate system is with the origin at the centre of the lens of the sensor, its Z-axis points to the direction of the look vector, Y-axis is along to the zenith, and the X-axis is completed by right-hand rule.