Algorithms & Methods

Innovation: Multipath Minimization Method

July 1, 2011By
Fig2-W(top)

Mitigation Through Adaptive Filtering for Machine Automation Applications
Multipath is real and omnipresent, a detriment when GPS is used for positioning, navigation, and timing. The authors look at a technique to reduce multipath by using a pair of antennas on a moving vehicle together with a sophisticated mathematical model. This reduces the level of multipath on carrier-phase observations and thereby improves the accuracy of the vehicle’s position. read more

This article is tagged with , and posted in Algorithms & Methods, Design & Test, From the Magazine, Innovation

Innovation: Doppler-Aided Positioning

May 1, 2011By
Figure 1. Satellite tracking and carrier-phase anomaly summary during the observation time-span. These data were collected in a dense urban environment in both static and kinematic mode. The superimposed red-points show epochs where carrier-phase observables are either missing or contaminated with cycle slips, loss of locks, and/or other measurement anomalies.

Improving Single-Frequency RTK in the Urban Enviornment
A look at how Doppler measurements can be used to smooth noisy code-based pseudoranges to improve the precision of autonomous positioning as well as to improve the availability of single-frequency real-time kinematic positioning, especially in urban environments. read more

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

Innovation: Accuracy versus Precision

May 1, 2010By
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A Primer on GPS Truth
True to its word origins, accuracy demands careful and thoughtful work. This article provides a close look at the differences between the precision and accuracy of GPS-determined positions, and should alleviate the confusion between the terms — making abuse of the truth perhaps less likely in the business of GPS positioning. read more

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

Innovation: Hybrid Positioning

March 1, 2010By
Figure 11. The electronic car used in the test.

A Prototype System for Navigation in GPS-Challenged Environments
A team of Australian and U.S. researchers have integrated a ground-based system with GPS and INS to create a hybrid system that provides precise and accurate position information continuously in a variety of environments where GPS alone comes up short. read more

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Multi-Sensor, Multi-Network Positioning

February 1, 2010By
FIGURE 1. Sample WLAN or Bluetooth fingerprint map, in meters.

Currently, no single technology, system, or sensor can provide a positioning solution any time, anywhere. The key is to utilize multiple technologies. We are now exploring a multi-sensor multi-network (MSMN) approach for a seamless indoor-outdoor solution. Its hardware platform is described in the previous article. The digital signal processor (DSP) is embedded in the GPS module. All sensors are integrated to the DSP that hosts core software for real-time sensor data acquisition and real-time processing to estimate user location. A smartphone handset provides wireless network measurements. read more

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

Innovation: Collective Detection

January 1, 2010By
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Enhancing GNSS Receiver Sensitivity by Combining Signals from Multiple Satellites
A new approach to enhancing signal sensitivity combines the received signal power from multiple satellites in a direct-to-navigation solution. read more

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Innovation: Improving Dilution of Precision

November 1, 2009By
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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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