外文翻譯---gps全球衛(wèi)星定位系統(tǒng)-文庫吧資料
2025-01-23 23:23本頁面
【正文】 ly 19 and 24 cm, respectively).The satellite signals consist of the Lband carrier waves modulated with a Standard or英文文獻The Global Positioning SystemThe global Positioning System (GPS) is revolutionizing surveying technology, Like its predecessor , the TEANSIT Doppler system, GPS shifts the scene of surveying operations from groundtoground measurements to groundtosky , with obvious implications : intervisibility of marks is no longer a criteion for their location 。 operations are possible in nearly all kinds of weather and be performed during day or night 。S code (formerly called the C/A code),a Precise or P code and a Navigation Message containing, amongst other things ,the coordinates of the satellites as functions of timethe Broadcast Ephemerides. The S code which is intended mainly for civilian use , yields a range measurement precision of about 10 meter, The navigation service provided by this code is referred to as the Standard Positioning Service, The p code is intended for military and selected civilian use only and yields a measurement precision of about 1 meter, The navigation service provided by the P code is therefore referred to as the Precise Positioning Service (PPS) Although both codes can be used for surveying , a more accurate method is to measure the phase of the carrier signal , For this reason , we will not discuss the detailed characteristics of the codes in this monograph . There are currently eight usable satellites in orbit. These are the experimental, ”Block 1” satellites, which will be progressively replaced as the “block 2”, operational satellites are placed into orbit beginning in 1989 the system should be plete, with 18 satellites in six orbital planesat about 20200 km altitude, allowing for simultaneous visibility of at least four satellites at any time of day almost anywhere in the world. The present constellation of satellites is configured to provide the most favorable geometry for testing the system over North America.As it happens, the observation geometry is equally favorable in Australia, and it i
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