The Global Positioning System, GPS technology has been widely used in positioning and attitude determination. It is well known that the accuracy, availability and reliability of the positioning results are heavily dependent on the number and geometric distribution of tracked GPS satellites. Because of this limitation, in some situations, such as in urban canyons, underground space or inside of ...

This report describes the key elements and results of Stanford University’s contribution to the development of the Wide Area Augmentation System (WAAS) and its underlying technologies. The Wide Area Augmentation System (WAAS) became the first operational space based augmentation system (SBAS) in July 2003. WAAS augments the Global Positioning System (GPS) with the following three services: inte...

The global positioning system (GPS) has found application in many different fields, in areas where there is a good line-of-sight (LoS) to GPS satellites, this technique provides a good estimate of the location of user terminal (UT). However, in indoor and dense urban environments, localization has always been a more challenging problem for several reasons. Typically the GPS signal is not strong...

Natural hazards including earthquakes, volcanic eruptions and tsunamis have been significant threats to humans throughout recorded history. Global navigation satellite systems (GNSS; including the Global Positioning System (GPS)) receivers have become primary sensors to measure signatures associated with natural hazards. These signatures typically include GPS-derived seismic deformation measure...

Reliable and precise electrical wave measurements are essential to the stability and efficiency of a power system. Phasor Measurement Units (PMUs), also known as synchrophasors, are devices that provide precise synchronized voltage magnitude and phase measurements at a high sampling frequency. Widely regarded as one of the most vital devices in monitoring and control for the future of power sys...

Deep and frequent Global Positioning System (GPS) signal fading due to strong ionospheric scintillation is a major concern for GPSguided aviation in equatorial areas during high solar activity. A GPS aviation receiver may lose carrier tracking lock under deep fading, and a lost channel cannot be used for position calculation until lock is reestablished. Hence, frequent loss of lock due to frequ...

This report describes the key elements and results of Stanford University’s contribution to the development of the Wide Area Augmentation System (WAAS), its underlying technologies, and alternative methods to provide global vertical guidance to aircraft. WAAS became the first operational space based augmentation system (SBAS) in July 2003. WAAS augments the Global Positioning System (GPS) with ...

A three-dimensional ray tracing model with aiming algorithms for global positioning system (GPS) signal is proposed to make simulations conform to the realistic radio occultation (RO) signal propagation. The two aiming algorithms used in this study ensure the initial and end point ray trajectories are located in the prescribed region. In past studies, the ray tracing techniques applied to the R...

In this paper, we present the design of a Software Defined Radio (SDR) architecture that is used for geotagging camera images. In this architecture, only the radio frequency (RF) front-end of the SDR is installed on the camera to reduce the power required for collecting Global Positioning System (GPS) geolocation data. A brief snapshot of the GPS signals is collected when a picture is taken and...

Global Navigation Satellites Systems (GNSS) such as the Global Positioning Systems (GPS) are well known for their ability to obtain position regardless of where in the world they operate. In order to function properly, GPS generally requires that a minimum of 4 satellite signals be present at any given time, in order to solve for three dimensions, and local receiver time offset. This minimum re...