A GNSS Code Multipath Model for Semi-Urban, Aircraft, and Ship Environments

Abstract

The University of Colorado Advanced GNSS Multipath Model integrates 3D structure models, electromagnetic ray-tracing algorithms, antenna pattern measurements, and detailed receiver tracking loop models to simulate code multipath errors. This article presents results for three environments -a semi-urban rooftop, an F-18 aircraft, and the aircraft carrier USS Eisenhower. Model accuracy is evaluated on the basis of multipath error statistics as well as time history amplitude and frequency content. In general, 1-s error statistics for all scenarios match the experimental data to within 15 cm, and time history comparisons often show good agreement in terms of amplitude and temporal variability. Frequency content is compared on the basis of a cross-correlation metric, with values of 0.57 or better for at least 67% of the data points. We also demonstrate the application of the modeling tools for the evaluation of additional antenna placements, reflector identification, and the characterization of key multipath signal properties.

A GNSS Code Multipath Model for Semi-Urban, Aircraft, and Ship Environments

“…One can see that the model generally captures frequency components correctly, but that amplitudes are too high, especially after 8 hours. This was true of much of the data set [26]. The cross-correlation results, given in Figure 12, are also not as good as for the roof-top, but nonetheless yield 30% of the correlation data above 0.9 and 67% above 0.57.…”

RF Replay System for Narrowband GNSS IF Signals

“…First, multipath is modeled inside the simulator using separate hardware channels and the number of channels is limited. Secondly, the required information to accurately model a specific environment, using for example raytracing as in Jülg [1] or Weiss et al [2], is generally not available. Unfortunately, this method is not available for users of hardware-based receivers, where the options for performance evaluation are either field tests (time consuming) or simulator scenarios.…”

A Ray-Tracing Technique to Characterize GPS Multipath in the Frequency Domain

“…Not much focus is given on using the ray-tracing based technique to study Doppler frequency differences. The ray-tracing technique facilitates accurate simulation of reflected signals in an urban environment using an urban city model [21]. As reported by Irsigler [23], Doppler frequency differences are very small and therefore a standard receiver cannot resolve them in its tracking loops.…”

“…The simulation was carried out for 10 minutes using the real PRN passes computed using the ephemeris. PRNs 14,18,19,21,22, and 27, which were visible at that location, were selected for the analysis. Looking at the geometry formed by the PRNs, building reflectors, and the test location, it was concluded that PRNs 14, 19, 21, and 27 had a high probability of producing multipath signals.…”

“…Eissfeller and Winkel [19] and Franchois and Roelens [20] describe a mathematical model for multipath and discuss numerical results with respect to pseudorange errors. Weiss et al [21] discuss a GNSS code multipath model for semiurban, aircraft, and ship environments using the ray-tracing technique and present a comparison of simulated and real data results with focus on pseudorange error occurrence, multipath temporal variability, and amplitude. Lau and Cross [22] present a ray-tracing approach to study carrier-phase multipath effects.…”