《定位系統(tǒng)》ppt課件-全文預(yù)覽
【正文】 satellites are in view ?It can be as rough as 100’s of kms ? We can also give synchronisation information to aid the GPS receiver to acquire the satellite’s signals: doppler shift and code phase delay. ?We allow the receiver to (coherently) accumulate more signal higher SNR! better sensitivity ?The receiver starts looking for the satellites right where they are timing information it is “immediately” extracted ? We can then provide the navigation data to the GPS receiver, and then we do not need to wait to decode the data from the satellite ? This is achieved by having a reference GPS receiver station which is constantly receiving and decoding the GPS signals in view and extracting signal parameters (navigation data, signal doppler and signal delay) The concept of AGPS ? A GPS monitoring station constantly receives signals from all visible satellites ? It stores the navigation data, together with SV acquisition data ? The AGPS receiver is relatively close to the monitoring station so that it sees the same SVs. ? The GPS receiver can request assisting data and then use it for a fast TTFF ? The reference receiver sends signal measurements. SV1 – Code phase: chips – Doppler: Hz – Navigation data SV2 – Code phase: chips – Doppler: Hz – Navigation data SV3 – Code phase: chips – Doppler: Hz – Navigation data … 827 1,467 135 +54 1008 190 8261,4771345310091888251,4891335110101878241,50313250 1011186Dti Dfi Lat: 43176。坐標(biāo)原點(diǎn)為地球質(zhì)心，其 地心空間直角坐標(biāo)系 的 Z軸指向 BIH （國際時間）（ CTP)方向，X軸指向 BIH CTP赤道的交點(diǎn)， Y軸與 Z軸、 X軸垂直構(gòu)成 右手坐標(biāo)系 ，稱為 1984年世界大地坐標(biāo)系統(tǒng) 。 ? 一部分是對每一個用戶接收機(jī)所共有的，例如：衛(wèi)星鐘誤差、星歷誤差、電離層誤差、對流層誤差等； ? 第二部分為不能由用戶測量或由校正模型來計算的傳播延遲誤差； ? 第三部分為各用戶接收機(jī)所固有的誤差，例如內(nèi)部噪聲、通道延遲、多徑效應(yīng)等?，F(xiàn)在用在原子鐘里的元素有氫 (Hydrogen)、 銫 (Cesium)、 銣 (Russium)等。 GPS接收機(jī)接收此信息，使之與自身的時鐘同步，獲得準(zhǔn)確的時間。 導(dǎo)航電文包括 衛(wèi)星星歷、工作狀況、時鐘改正、電離層時延修正、大氣折射修正等信息。由于大氣層電離層的干擾，這一距離并不是用戶與衛(wèi)星之間的真實(shí)距離，而是 偽距 （ PR）。 ?地面監(jiān)控部分 （全部在美國境內(nèi)） ?1個主控中心（另有 1個備用） ?4個專用地面天線 ?6個專用監(jiān)視站 ?用戶設(shè)備部分 ?GPS接收機(jī) ? 已知 A、 B、 C三個節(jié)點(diǎn)的坐標(biāo)，以及它們到節(jié)點(diǎn) D的距離，確定節(jié)點(diǎn) D的坐標(biāo) GPS：定位原理 If you know the distance to 4 KNOWN locations: The fourth sphere (not shown) will intersect only one of these two locations. How does 3dimensional (3D) positioning work? 3 Dimensional Fix! GPS Receiver Position Calculation The location will be somewhere on the surface of the sphere The two spheres will intersect for
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