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GPS (Global Positioning System) is a satellite-based positioning and navigation system owned and operated by the US Department of Defense. GPS satellites circle the earth twice a day in a very precise orbit and transmit signal information to earth. GPS receivers take this information and use triangulation to calculate the exact position of them. GPS receiver compares the time a signal was transmitted by a satellite with the time it was received. The time difference tells the GPS receiver how far away the satellite is. With the distance measurements from a few more satellites, the receiver can determine its position with centimeter accuracy.
TOTAL STATION SURVEY
A total station is an optical instrument used in modern surveying. It is a combination of an electronic theodolite (transit), an electronic distance meter (EDM) and software running on an external computer known as data collector. A total station allows the surveyor to store all information he needs to establish a setting out and can store all information taken from site as existing features, original ground levels, road edges, etc.
Also the remote measurements are facilitated by the total station where a direct access is not available. For example the height of street light poles, ground clearance of overhead power lines, etc.
A theodolite is an instrument for measuring both horizontal and vertical angles, as used in triangulation networks. It is the old, mechanical / manual version of total station. Theodolite survey widely using for single line executions like pipe lines, cable routes, curb lines, road centre lines, etc.
A modern theodolite consists of a movable telescope mounted within two perpendicular axes-the horizontal or trunnion axis, and the vertical axis. When the telescope is pointed at a desired object, the angle of each of these axes can be measured with great precision, typically on the scale of arcseconds.
DUMPY LEVELS SURVEY
A dumpy level is an optical instrument used in surveying to transfer, measure, or set horizontal levels with reference to the mean sea level or available approved datum precisely. The instrument and staff are used to gather and/or transfer elevations (levels) during site surveys.
Measurement generally starts from a benchmark with known height determined by a previous survey, or an arbitrary point with an assumed height.
Utility surveying is the process of identifying public utility mains that are located underground. Utility surveying accounts for lines that serve telecommunication, electricity distribution, natural gas, cable television, fiber optics, traffic lights, street lights, storm drains, water mains, and waste water pipes. Also, in most cases, major oil and gas pipelines, national defense communication lines, mass transit, rail and road tunnels etc run beneath the ground level.
Since different types of underground utilities are made of different materials, different kind of detection and location methods have to be used.
This involves determination of vehicle or pedestrian numbers, vehicle types, vehicle speeds, as well as information such as trip length, trip purpose and trip frequency.
Transportation planning based on the results of an in-depth traffic surveying could directly contribute to better efficiency and life of roads, provide better means to utilize other roads in case of special events in the locality, and altogether help the development of roads and infrastructure.
Contour map of an area serves as the direct indicator of the ground profile at that area. Many times in the case of site suitability studies, an engineer has to analyze the contour map of the area, and identify the nature of the ground, and finally works out the suitability of the site for the project works to be taken up. Contour maps helps in finding out depth of cutting and filling, if formation level of road/railway is decided. The routes of the road, railway, canal or sewer lines could be planned such that the earthwork and excavation are minimized and balanced with the help of such an analysis. From the contours, it is possible to determine the capacity of a reservoir. The stock volume of materials that are piled up on the ground (e.g.: quarries) could be estimated using the values provided by a contour map of the area. Further, in the hydrology domain, a contour map helps calculate the catchment area and reservoir capacity, hence quantity of water flow at any point of a water body which is useful in pointing out the flood levels of the concerned water body.