Issue link: https://autonomy.trimble.com/en/resources/i/1410500
TECHNICAL PUBLICATION WHAT IS TRIMBLE DOING ABOUT GNSS MULTIPATH? Everest Plus has several components contributing to the resulting multipath improvements: ► An improved tracking discriminator which inherently reduces the amount of multipath on the raw measurement. ► Additional information is extracted from the hardware to go into a multipath estimator. ► A neural network has been added that takes data from the hardware and derives an improved multipath estimate which is removed from the pseudorange observables. ► Improvements in code/carrier filter for PVT solution to better handle challenging environments. For example driving in a built up area, around trees and freeway applications. Figure 1 shows these improvements, derived from the raw pseudorange without the code/ carrier filter. The data shows the well-known MP1 estimate, filtered with a 10 second time constant. The blue curve shows the pseudorange multipath on L1 from legacy Everest, the green shows the multipath from Everest Plus. In this example the multipath reduction is over 50%. Evaluating all GPS satellites from the same data set in a rooftop environment yields an average multipath reduction of 31% with the new technique (Figure 2). To evaluate the positioning improvements of Everest Plus dynamic tests were performed compared to a high precision GNSS/INS post processed truth reference. Data was collected in the following environments: ► Freeway ► Downtown San Jose ► Open Parking Lot ► Trimble Campus – walking pace ► Urban The data included mostly dynamic data, but also static sections such as stops at gas stations, traffic lights, stop signs and covered a variety of traffic speeds. The summary statistics are tabulated below. The Time column provides the total duration for each environment classification. Overall we get an improvement in the 2D 95th percentile of between 15% and 30% in the SBAS pseudorange solution depending on the environment. Sub-meter 95% performance was delivered in all environments except downtown San Jose and the Trimble campus where the vehicle was driven very close to buildings and trees. MP1 (cm) PRN Everest Everest+ Reduction 1 21.6 20.2 6.48% 3 33.0 31.1 5.76% 8 27.4 21.5 21.53% 10 20.5 11.9 41.95% 11 23.4 15.0 35.90% 14 12.1 13.3 -9.92% 18 35.4 16.2 54.24% 21 41.4 22.3 45.74% 22 23.6 20.7 12.29% 24 41.1 19.5 52.55% 27 27.8 16.4 41.01% 31 21.6 18.7 13.43% 32 13.4 9.7 27.61% Average 26.3 18.2 30.85% Figure 1 Figure 2 TRANSFORMING THE WAY THE WORLD WORKS