The Smartphone Revolution

December 1, 2009By

Seven technologies put GPS in mobile phones around the world. Here is the how and why of location’s entry into modern consumer mobile communications. read more

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On the Edge: Multipath Measures Snow Depth

November 1, 2009By
FIGURE 2. Snow depth derived from GPS (red squares), the three ultrasonic snow depth sensors (blue lines), and field measurements (black diamonds). Bars on field observations are one standard deviation. GPS snow-depth estimates during the first storm (doy 85.5–86.5) are not shown (gray region) because the SNR data indicate that snow was on top of the antenna.

The September “Innovation” column in this magazine, “It’s Not All Bad: Understanding and Using GNSS Multipath,” by Andria Bilich and Kristine Larson (see www.gpsworld.com/multipath), mentions the use of multipath in studying soil moisture, ocean altimetry and winds, and snow sensing. An experiment the authors conducted, designed to study soil moisture, yielded a surprise bonus: a new methodology for measuring snow depth via GPS multipath. It has important implications for weather and flood forecasting, and could also bring new insight to bear on GPS antenna design. read more

Higher Timing Accuracy, Lower Cost

November 1, 2009By
AURORA BOREALIS seen from Churchill, Manitoba, Canada. Ionospheric scintillation research can benefit from this new method.

Inside a typical GNSS receiver, the estimate of the error in the local oscillator is formed as a component of the navigation solution, which is in turn based on the output of each satellite-tracking channel propagating its estimate of carrier and code measurements to a common future point. But this method limits the resolution with which the noise of the local oscillator can be quantified. To bypass this shortcoming requires a method of coherently gathering information about the phase change in the local oscillator across all available satellite signals: to use the same samples simultaneously for all satellites in view to estimate the center-point phase error common across the visible constellation. We explore how. read more

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Innovation: Improving Dilution of Precision

November 1, 2009By

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

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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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