Design & Test

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

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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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Innovation: GNSS Antennas

February 1, 2009By
FIGURE 7. Quantifying multipath caused by vertical object reflections.

An Introduction to Bandwidth, Gain Pattern, Polarization and All That
How do you find best antenna for particular GNSS application, taking into account size, cost, and capability? We look at the basics of GNSS antennas, introducing the various properties and trade-offs that affect functionality and performance. Armed with this information, you should be better able to interpret antenna specifications and to select the right antenna for your next job. read more

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Innovation: Tsunami Detection by GPS

February 1, 2008By
QuickBird satellite image of Kalutara Beach on the southwestern coast of Sri Lanka showing the receding waters and beach damage from the Sumatra tsunami.

How Ionospheric Observations Might Improve the Global Warning System
Recent investigations have demonstrated that GPS might be an effective tool for improving the tsumani early-warning system through rapid determination of earthquake magnitude using data from GPS networks. A less obvious approach is to use the GPS data to look for the tsunami signature in the ionosphere. 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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