Passive Altimeter Study Using GPS Flight Data (Preprint)
Passive Altimeter Study Using GPS Flight Data (Preprint)
复制标题
使用 GPS 飞行数据进行被动高度计研究（预印本）
DOI：
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
Y. Morton
中科院分区：
文献类型：
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作者：
L. L. Liou;J. Tsui;D. Lin;J. Schamus;F. Graas;Y. Morton
摘要：给出了利用 GPS 信号的陆上无源高度计应用的软件 GPS 接收器结果。飞行数据是使用俄亥俄大学运营的 DC-3 飞机收集的。这次飞行发生在俄亥俄州东南部上空，那里地形丘陵，森林茂密。飞机上的 GPS 接收器包含两个通道。第一个通道具有朝上的右旋圆极化天线，第二个通道具有朝下的左旋圆极化天线。向上天线主要接收GPS直达信号，而向下天线主要接收地面反射GPS信号。软件无线电 GPS 算法用于处理从上行信道接收的数据。处理后获得的信息包括接收机位置数据、可见卫星、C/A码延迟、多普勒频率和作为时间函数的导航数据位。该信息用于生成参考信号以关联从下行信道接收的数据。由于参考信号和反射信号之间的多普勒频移可能不同，因此相干积分时间的长度受到限制。此外，反射信号的多普勒频移会随着地形的变化而快速变化。因此，相干和非相干积分的组合被用来增强反射信号的信噪比。相关结果显示了与直接信号和反射信号之间的路径长度差相对应的 C/A 码延迟。根据接收器和卫星的已知位置，可以计算出接收器距地面的高度。飞行数据覆盖地面以上 0 米至 3000 米的高度。
Abstract : Software GPS receiver results are presented for an over-land, passive altimeter application utilizing GPS signals. The flight data were collected using a DC-3 aircraft operated by Ohio University. The flight took place over southeast Ohio, where the terrain is hilly and forested. The GPS receiver on board the aircraft contains two channels. One channel has a right-hand-circular-polarized antenna facing upward, and the second has a left-hand-circular-polarized antenna facing downward. The upward antenna primarily receives the GPS direct signals, while the downward antenna primarily receives the ground-reflected GPS signals. Software radio GPS algorithms are used to process the data received from the upward channel. The information obtained after processing includes receiver position data, visible satellites, C/A code delay, Doppler frequency and navigation data bits as functions of time. This information is used to generate a reference signal to correlate the data received from the downward channel. Since the Doppler shift can be different between the reference and the reflected signals, the length of the coherent integration time is limited. Furthermore, the Doppler shift of the reflected signal can change rapidly as a function of the terrain. Therefore, a combination of coherent and noncoherent integration is used to enhance the signal-to-noise ratio of the reflected signals. The correlation result shows a C/A code delay corresponding to the path length difference between the direct and reflected signals. From the known locations of the receiver and the satellites, the height above ground of the receiver can be calculated. The flight data cover heights ranging from 0 to 3000 meters above the terrain.