摘要
为了满足民用航空用户在精密进场与着陆中的应用需求,美国联邦航空管理局设计了GPS局域增强系统(Local Area Augmention System,LAAS)。LAAS地面站设备采用3-4个安装在机场固定已知点的高性能GPS接收机,观测所有可见卫星,并将这些观测数据同时发送给处理单元,处理单元将码相位测量的伪距数据进行载波相位平滑,同时使用差分技术获得每颗可用卫星的误差修正值,并进行完善性监测,最后利用甚高频(VHF)广播这些修正数据。当某颗卫星出现故障后,整个系统的可用性发生改变。通过仿真研究可以得到当可见卫星数量在6颗或6颗以上时,减少一个卫星对完善性影响不大,甚至会变好,在可见卫星为5颗的时候较少一个完善性的可用性降低。并且完善性还和卫星的几何分布有关。
The Local Area Augmention System （LAAS） is an augmentation of the Global Positioning System to allow for precision approach and landing at airports. The LGF includes a small collection （typically 3 to 4） of GPS reference receivers and antennas placed at precisely known locations, observes all of the satellites and sends the observed data to unit of processing. Finally, the corrections ,along with integrity parameters and approach-path information, are broadcast to approaching aircraft via a Very High Frequency（VHF） data link. When a satellite failed, the availability and integrity will change. The value of VPL will decrease when one of only five visible satellites failed. But, when the visible satellites were six or more, the value of VPL change infinitesimally, and increase sometimes. The integrity is also correlation to the distribution of GPS.
出处
《指挥控制与仿真》
2009年第4期87-89,96,共4页
Command Control & Simulation
