城市典型环境下单频导航型GNSS接收机多路径误差特性分析

Multipath Error Analysis of Single Frequency Navigation GNSS Receiver in Typical Urban Environment

在高大建筑物、树木遮挡等城市复杂环境中,多路径误差和纯反射(NLOS)信号误差难以准确建模,严重影响行人GNSS导航定位的精度和可用性。本文首先对比分析了多路径延迟和纯反射信号延迟的误差特性,然后利用双差观测方程提取多路径和NLOS延迟误差,分析了两种延迟误差对伪距、载波相位和多普勒观测值的影响。通过UBLOX-NEO-M8T单频导航型接收机在建筑物附近和树木遮挡两种观测环境下的实测数据处理与分析,结果表明:载噪比(C/N0)较小时多普勒噪声明显变大。对于M8T导航型接收机,多路径影响严重的环境下C/N0低于30 d BHz,多普勒噪声变大。而NLOS影响严重的环境下多普勒噪声与C/N0之间关系不明显,在较大的C/N0,多普勒噪声仍然很大;在树木遮挡时,主要受多路径效应的影响,引起伪距的误差量级在10~150 m之间,对相位和多普勒的影响不明显;在高楼遮挡时,会出现NLOS信号干扰,对伪距和载波相位观测值的影响相同,延迟量大小与反射点的距离有关,可达到几百米,对多普勒观测值也有明显影响。

In the complex urban environment such as tall buildings and trees, multipath error and non-line-of-sight （NLOS） signal error can＇t be modeled accurately,which badly affect the accuracy and usability of pedestrian GNSS navigation and positioning.This paper comparatively analyses the characteristics of multipath error and NLOS signal error at first, and then separates multipath error and NLOS signal error using double difference observation equation to analyze the influence on pseudo range, carrier phase and doppler of two kind error.By analysing the data measured by UBLOX-NEO-MST single frequency navigation GNSS reeeiver beside tall buildings or trees,the results show that Doppler noise is significantly larger when C/N0 is small.For M8T navigation receiver, Doppler noise becomes larger when C/N0 is lower than 30 dBHz under Multi-path seriously affected environment.The relationship between Doppler noise and C/N0 is not obvious under NLOS seriously affected environment.Doppler noise is still significant when C/N0 is larger.Satellite signal is mainly affected by the multipath effect when the trees are obscured,which causes pseudo range error is between 10- 50 m, and the impact on phase and Doppler is not obvious.Satellite signal is mainly affected by NLOS when tall buildings are obscured,which causes the same effect on pseudorange and carrier phase observations.The amount of the delay depends on the distance between the reflection point and the receiver,sometimes can reach a few hundred meters.Doppler observations also have a significant impact.