GPS, CONCPTS ,PRNCIPELS &APPLICATIONS 14/04/2019 GPS, CONCPTS ,PRNCIPELS &APPLICATIONS sokkia saudi survey sys

sokkia saudi survey sys. Introduction :- The Global Positioning System (GPS) is a satellite-based navigation system made up of a network of 24 satellites placed into orbit by the U.S. Department of Defense. GPS was originally intended for military applications, but in the 1980s, the government made the system available for civilian use. GPS works in any weather conditions, anywhere in the world, 24 hours a day. There are no subscription fees or setup charges to use GPS. sokkia saudi survey sys.

sokkia saudi survey sys. The system's positioning and timing data are used for a variety of applications, including air, land and sea navigation, vehicle and vessel tracking, surveying and mapping ,asset and natural Resource management. GPS is the shortened form of NAVSTAR GPS. This is an acronym for Navigation system with Time and Ranging. sokkia saudi survey sys.

sokkia saudi survey sys. The GPS SYS is composed of a constellation of satellites orbiting approximately 20,000 km (about 12,500 miles) above the Earth. The full constellation is defined as 24 satellites. sokkia saudi survey sys.

sokkia saudi survey sys. The satellites are arrayed in 6 separate orbits, each inclined about 55° with respect to the equator. The orbit is traversed in about 12 hours. With a full constellation, receivers located on most spots on the Earth can see at least 6 satellites, and sometimes as many as 12 of the satellites at any one time. sokkia saudi survey sys.

sokkia saudi survey sys. GPS receivers use triangulation to calculate the user's exact location Precise microwave signals are transmitted from the satellites, allowing a GPS receiver to determine its location, speed and direction. sokkia saudi survey sys.

sokkia saudi survey sys.

sokkia saudi survey sys.

sokkia saudi survey sys. Competitors of GPS GLONASS - Russian Federation’s satellite navigation system Galileo -European Union and the European Space Agency sokkia saudi survey sys.

sokkia saudi survey sys. The receiver can compute its position using trilateration. Three spheres intersect at a point, there are 3 distances or ranges to resolve, latitude, longitude and height. tracking four satellites is required in order to correct the receiver's clock error. Here there are four ranges to resolve, latitude, longitude, height and time. Using just the receiver, (NAVIGATOR)accuracies are about +/- 10metres sokkia saudi survey sys.

Three Segments of the GPS Space Segment User Segment Three Segments of the Global Positioning System The Global Positioning System is comprised of three segments: the Control Segment, Space Segment and User Segment. Control Segment Ground Antennas Master Station Monitor Stations

sokkia saudi survey sys. Segments of GPS System This system consists of three segments:- the space segment. the control segment and the user segment sokkia saudi survey sys.

sokkia saudi survey sys. space segment 1- The GPS space segment consists of a constellation of satellites transmitting radio signals to users. The Air Force manages the constellation to ensure the availability of at least 24 GPS satellites. sokkia saudi survey sys.

sokkia saudi survey sys. THE CONTROL SEGMENT This part consists of 5 worldwide base-stations that monitor the satellites to track their exact position in space, and to make sure that they are operating correctly. The stations constantly monitor the orbits of the satellites and use very precise radar to check altitude, position and speed. sokkia saudi survey sys.

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sokkia saudi survey sys. THE USER SEGMENT Consists of the GPS Receiver equipment's which receives the signals from the GPS satellites and uses the transmitted information to calculate the user location. sokkia saudi survey sys.

single point positioning In single point positioning coordinates of a receiver at an "unknown" point are sought with respect to the earth's reference frame by using the "known" positions of the GPS satellites being tracked. sokkia saudi survey sys.

Point positioning Fig. 1:Point Positioning of GPS receiver In this figure, s1, s2, s3 and s4 represent four different satellites (least required) being tracked. The positions of these satellites are referenced to the centre of the earth in the X, Y, Z coordinate frame. The coordinates for s1 are shown as (xs1, ys1, zs1). The coordinates of r, the unknown point, as referenced to the centre of the earth, are assumed to be (xr, yr, zr). The observed code, Prs1, relates the known coordinates of satellite 1 with the unknown coordinates of the receiver using the equation for a line in three-dimensional space. That is, Prs1 = [(Xs1 - Xr)2 + (Ys1 - Yr)2 + (Zs1 - Zr)2] + error Thus, from four satellites, four distance equation can be formed leading to computation of the four unknowns (xr, yr, zr and clock bias) can be computed.

sokkia saudi survey sys. Relative positioning The concept of relative positioning is Instead of determining the position of one point on the earth with respect to the satellites (as done in single point positioning), the position of one point on the earth is determined with respect to another "known" point. sokkia saudi survey sys.

sokkia saudi survey sys. differential positioning (DGPS) The accuracy can be improved by using two or more receivers which will give ‘differential’ position (DGPS). It is possible to know the position of B in relation to A when the co-ordinates of A are known and the satellites are tracked simultaneously. In this situation, (A) would be called a reference station, or base station and( B) would be called a Rover. sokkia saudi survey sys.

sokkia saudi survey sys. GPS TECHNIQES Static Positioning :- - it used when we want to establish control points from known points. - This method provides the highest accuracy and requires long observation times. - This method requires post processing software sokkia saudi survey sys.

sokkia saudi survey sys. * * Time in unknown point =10mint +2xdist (km) accuracy :- 3 mm + 0.5 X dist (Km) Hz 5 mm +0.5 x dis(Km) V Example for base line length 10km :- Time = 10 + 2x 10km = 30 mint. Accuracy = 3mm + 0.5x10 = 8mm Hz 5mm + 0.5x10 = 10mm v BASE (known point) Unknown point sokkia saudi survey sys.

(RTK( REAL TIME KINEMATIC RTK GPS survey consist of a data transfer link and at least one GPS receiver over a known point usually a Control Survey Marker which remains stationary and a rover which moves from point to point In a RTK survey shots are taken from a fixed base station to a rover station, which then transfers the corrections to the rover. Sokkia Saudi survey sys.

(RTK( REAL TIME KINEMATIC Occupation times for the rover are generally a few seconds to a few minutes Effective for areas with a clear view of the horizon No need for post processing software . BASE ROVER sokkia saudi survey sys.

sokkia saudi survey sys. GPS Coordinate System GPS measurements are referenced to the 1984 World Geodetic System reference ellipsoid, known as WGS84. It is better to display and store results in terms of a local coordinate system. Before you start a survey, choose a coordinate system. Depending on the requirements of the survey, you can choose to give the results in the national coordinate system, a local coordinate grid system, or as local geodetic coordinates. When you have chosen a coordinate system, search your survey archives for any horizontal and vertical control points in that coordinate system that are in the area to be surveyed. You can use these to calibrate a GPS survey. sokkia saudi survey sys.

Local Coordinate Systems A local coordinate system simply transforms measurements from a curved surface (the earth) onto a flat surface (a map or plan). Four important elements constitute a local coordinate system: local datum datum transformation map projection calibration (horizontal and vertical adjustments) When you survey using GPS, consider each of these. sokkia saudi survey sys.

Earth Ellipsoid An Earth ellipsoid is a mathematical figure approximating the shape of the Earth, used as a reference frame for computations in geodesy, astronomy and the geosciences. Various different ellipsoids have been used as approximations.

sokkia saudi survey sys. Using a Geoid Model The geoid is a surface of constant gravitational potential that approximates mean sea level.(assume if the sea covered the earth) it is used with the GPS ellipsoid height observations to provide an estimate of elevation. sokkia saudi survey sys.

Ellipsoid Scale Factor This scale factor accounts for the height of the ground above the reference surface (the ellipsoid). This scale factor is defined geometrically: Consider the following diagram: Dist ground/(R+h) = dist elip/R Dist elip/dist ground = R/(R+h) kelip = R/ (R+h) sokkia saudi survey sys.

sokkia saudi survey sys. Applications of GPS Civil Engineering • Civil engineering firms utilize GPS systems for road construction projects, earth moving projects etc….. • Some earth moving projects can involve real-time differential data collection and display that links with the operator in the cab, allowing the person to determine if the correct grade has been reach • The same technology can also be utilized to properly place building foundations and other structural features sokkia saudi survey sys.

sokkia saudi survey sys. • Other engineering applications include the analysis of structural deformation for various features – Bridges – TV towers – Dams • GPS can also be utilized to analyze land subsidence caused by oil or groundwater extraction or mining sokkia saudi survey sys.

Example for the application of GPS in civil engineering In road construction and Earth moving, GPS, combined with wireless communication and computer systems, is installed onboard the Earthmoving machine. Designed surface information, in a digital format, is uploaded into the system. With the help of the computer display and the real-time GPS position information, the operator can view whether the correct grade has been reached. In situations in which millimeter-level elevation is needed, GPS can be integrated with rotated beam lasers sokkia saudi survey sys.

Road construction with GPS sokkia saudi survey sys.

sokkia saudi survey sys.

Mining • Surveys and drill patterns associated with mining were often completed using conventional methods • Stakes marking locations and transects would get misplaced or buried, and bits on drill rigs would be estimated for depth • Many mining operations now utilize RTK GPS which significantly improves accuracy regarding depth of drilling as well as direction of tunneling

Utilities • GPS can also be utilized in the utilities industry • Up-to-date maps of utilities are essential for utility companies – Maps allow companies to plan, build, and maintain their assets. • GPS can be used to gather precise location information about various lines, as well as any additional attribute information • Most line mapping requires little to no ground marking

14/04/2019 Forestry • Applications in the forestry industry include – fire prevention and control – harvesting operations – insect patterns – boundary determinations – aerial spraying sokkia saudi survey sys

Factors affecting accuracy Number of visible satellites Position dilution of precision Satellite elevations Multipath Distance between space station and rover receivers