Design & Test

Innovation: Improving Dilution of Precision

November 1, 2009By
Inn-T

A Companion Measure of Systematic Effects
GPS receivers must deal with measurements and models that have some degree of error, which gets propagated into the position solution. If the errors are systematically different for the different simultaneous pseudoranges, as is typically the case when trying to correct for ionospheric and tropospheric effects, these errors propagate into the receiver solution in a way that is fundamentally different from the way that random errors propagate. So in addition to dilution of precision, we need a companion measure of systematic effects. In this month’s column, we introduce just such a measure. read more

This article is tagged with and posted in Algorithms & Methods, Innovation

Innovation: It’s Not All Bad

October 1, 2009By
Mauna Kea GPS station MKEA, facing northwest

Understanding and Using GNSS Multipath
Telltale signs of multipath are the fluctuations in the signal-to-noise ratios (SNRs) reported by some GNSS receivers. In this month’s column, the authors look at how an analysis of SNR values can be used to map the multipath environment surrounding an antenna so that models of multipath can be constructed to further minimize its effect. Also, although an annoyance for most GNSS users, it turns out that multipath has its positive points. read more

This article is tagged with and posted in Algorithms & Methods, Innovation

Septentrio Launches Inertially Aided Receiver, Plus New AsteRx2eH

September 28, 2009By

Septentrio has launched two new products. The AsteRxi is the company’s first multi-sensor GNSS receiver. AsteRxi processes high-quality GNSS measurements with IMU-measurements to generate an enhanced integrated position. read more

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Photos from ION GNSS 2009

September 25, 2009By

Photos from ION GNSS 2009 in Savannah, Georgia read more

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Real-Time Software Receivers: Challenges, Status, Perspectives

September 1, 2009By
FIGURE 2. Single-instruction single-data versus single-instruction multiple-data.

By Marcel Baracchi-Frei, Grégoire Waelchli, Cyril Botteron, and Pierre-André Farine The idea of a software receiver is to replace the data processing implemented in hardware with software and to sample the analog input signal as close as possible to the antenna. Thus, the hardware is reduced to the minimum — antenna and analog-to-digital converters (ADCs) — while all the signal processing... read more

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Innovation: Where Is GIOVE-A Exactly?

July 1, 2009By
photo1

Using Microwaves and Laser Ranging for Precise Orbit Determination
Though Galileo’s GIOVE-A is a test satellite not necessarily ready for scientific use, orbit analyses with a reduced accuracy can help to identify weaknesses and suggest improvements. This month, the authors share work being carried out to precisely determine the orbit of GIOVE-A using SLR and microwave observations. This preliminary investigation will benefit the procedures to be implemented for the future Galileo constellation. read more

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Integer ambiguity validation: Still an open problem?

July 30, 2007By

By Sandra Verhagen High-precision Global Navigation Satellite System (GNSS) positioning results are obtained with carrier phase measurements, once the integer cycle ambiguities have been successfully resolved. The position solution is obtained in four steps: 1. Float solution:least-squares, discarding integer nature. 2. Integer solution: real-valued float ambiguities mapped to integer-valued ambiguities.Examples of integer estimators (Teunissen, 1998a): Integer Least-Squares: optimal, requires search... read more

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Antenna-Induced Biases in GNSS Receivers

May 17, 2007By

By Inder Jeet Gupta It is well known that the phase center of a GNSS antenna can vary with the satellite direction. This phase center movement leads to aspect dependent carrier phase and code phase biases in the satellite signal. For precise geo-location, one needs to characterize the antenna-induced carrier and code phase biases over the upper hemisphere. In the... read more