Magellan Roadmate 1700 Extended Mount
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Global Positioning System (GPS) is new tool used for either positioning of ground locatings or as for surveying. It has become very usual amid pros ranging from surveys to engineers to archaeologists. Many of them are using GPS on their survey work. For galore of us, it may seem complicated, but the principle is very simple. GPS stand for Global Positioning System which is a tool applied for locating ourselves on the earth. This tool ( based on satellite communicating system) was applied by United States Military and later extended to civilian use. It uses 4-orbital satellites (moving along 6-orbital planes) orbiting at an altitude of approximately 20200 Km each 12 hours. The communication or carrier waves broadcast from these satellites are employed to emplacement on a given ground position. In essence, the scheme uses a radio receiver (located on ground) that receive signal from satellites thereby locating it is geographic coordinates. More specifically, the ground receivers will transmit its' positions and time by making simultaneous measurements to the satellites. Then three orbiting satellites will derive the 2-d dimensional position or location. If 3 dimensional coordinates (latitude, longitude and height) are needed, it is necessary to commune with minimum of four satellites within the signal range. Use of GPS in Surveying GPS seems to be an splendid technique for surveying. In a heap of civil engineering fieldwork, it is applied widely at present. It is primarily employed for mapping, precise emplacement or the spots, world work, topographic surveys. In combining with other latest proficiencies it has become a ready substitute for the established surveying techniques. The selection of the type of GPS depends on the level of accuracy expected. Many engineers may be happy with the degree of accuracy possessed by hand-held GPS. This has been an necessary item ( or surveying tool) for field investigation and reconnaissance work. The hand kept one may not be the best equipment, where accuracy within a meter is required. For example, for surveying involving trench stakeouts, contour surveys and recording of websites at scales up to 1:2500, using of Differential GPS may be appropriate. For more precise recording, such as grid layouts, excavation plans and topographical surveys, Carrier-Phase GPS will have to be used. Thus implying very high level of accuracy up to millimeter. GPS Compared to Total Station Until lately the Total Station Theodolite (TST) has become the preferent tool for setting out of trenches, surveying websites or topographical surveys. Frequently in archaeological work, Now GPS has become the standard tool for galore surveying professionals. It outperformed TST when the work has to be done: o Where internet sites are remote and has fixed access, hard details are not available, and positioning may be unreliable. In addition, GPS may need less man power and less time to finish same coverage of TST. In other words, both setting up and surveying time is substantially reduced. When using GPS, one will have to recognise the masters and cons. There are limitations related with GPS. Since, this system depends on communication with satellite system, when carrying out surveys, clear sky have to be there. Similarly, you may detect poor satellite signal reception when in thick forest cover or close to tall buildings. Finally, it is necessary to know the cost of GPS. The cost may vary according to the level of accuracy you need. The accuracy comes with a price tag. |
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