Global Navigation Satellite Systems (GNSS) has become increasingly interwoven into the fabric of our infrastructure and economic system. However, as GNSS becomes more important for safety of life and economically critical infrastructure, subversive elements will be increasingly tempted to deny or spoof its signals. The fact that GNSS has vulnerabilities is well known and it is becoming recogniz...

Science-based instruments which use radio signals from Global Navigation Satellite Systems (GNSS) have been successfully deployed on several NASA missions. Applications range from Precise Orbit Determination (POD), limb sounding and formation flying. Remotely sensing the Earth's surface using reflected GNSS signals as a bi-static radar source (GNSS-R) is one of the most challenging applications...

A USRP-BASED FLEXIBLE GNSS SIGNAL RECORDING AND PLAYBACK SYSTEM: PERFORMANCE EVALUATION AND STUDY by Ruihui Di Global Navigation Satellite Systems (GNSS) signals are often subjected to both manmade and natural interferences such as RF jamming, ionosphere scintillation, multipath, and signal anomaly. In order to achieve desired navigation application performances, advanced receiver processing or...

Low-cost MEMS-based IMUs, video cameras and portable GNSS devices are commercially available for automotive applications and some manufacturers have already integrated such facilities into their vehicle systems. GNSS provides positioning, navigation and timing solutions to users worldwide. However, signal attenuation, reflections or blockages may give rise to positioning difficulties. As oppose...

Fast and reliable ambiguity resolution (AR) has been a continuing challenge for real-time precise positioning based on dual-frequency Global Navigation Satellite Systems (GNSS) carrier phase observation. New GNSS systems (i.e., GPS modernization, BDS (BeiDou Navigation Satellite System), GLONASS (Global Navigation Satellite System), and Galileo) will provide multiple-frequency signals. The GNSS...

Historically, the military has used special purpose Global Positioning System (GPS) radios for radio navigation. This has the disadvantage of locking users into fixed technology solutions designed to meet a fixed set of requirements. Software Defined Radios (SDR) have the advantage of being able to easily adapt to provide new capabilities using current generation technology. Continued improveme...

With the modernization of the GNSS, the techniques of multi-GNSS navigation and positioning are becoming increasingly important. For multi-GNSS double-difference data processing, a tight combination (TC) strategy can provide more observations and higher reliability, which emploies a single reference satellite for all observations from different GNSS. However, multi-GNSS will bring some challeng...

SUMMARY The applications of GPS can be found across almost all of a nation's economic, scientific and social activities. The major shortcoming of GNSS is that it is usable everywhere where there is clear sky, and hence fails to operate where it's impossible or difficult to receive the satellite signals. In some difficult signal environments – principally where the satellite signals are weak (<-...

A new global navigation satellite system (GNSS) carrier-phase attitude model and its solution are introduced in this contribution. This affine-constrained GNSS attitude model has the advantage that it avoids the computational complexity of the orthonormality-constrained GNSS attitude model, while it still has a significantly improved ambiguity resolution performance over its unconstrained count...

When applying the Global Navigation Satellite System (GNSS) for precise kinematic positioning in airborne and shipborne gravimetry, multiple GNSS receiving equipment is often fixed mounted on the kinematic platform carrying the gravimetry instrumentation. Thus, the distances among these GNSS antennas are known and invariant. This information can be used to improve the accuracy and reliability o...