JIMI Electronic

There are a variety of uses for GPS technology today, from basic positioning applications which might provide a traveller with their current location, speed, and direction to their destination, to highly complex applications where the user’s position information is feed into a system that provides location-specific features and services tailored for that user. What follows are some examples of how GPS technology is being used to enhance the capabilities of intelligent vehicle platforms. The initial examples illustrate some of the more traditional positioning applications, such as basic location and autonomous navigation systems, which are already seeing widespread use today. This is followed by examples describing how GPS-derived positioning information is being used to provide location-based services in vehicles today, and how the richness and complexity of those services will increase in the near future. A  portable tracker , while not strictly an intelligent vehicle system,...

There are many parameters used by the industry to assess the performance of a GPS receiver, and to evaluate the relative performance of comparable receivers. The most common parameters being used to evaluate GPS receiver performance include positioning and timing accuracy, time-to-first-fix, reacquisition time, and receiver sensitivity. Positioning and timing accuracy The most obvious of these parameters is positioning accuracy – how accurate are the positions calculated by an autonomous GPS receiver, based on the number of satellites that can be seen by that receiver? This is typically measured by performing a mapmatching test, where positions calculated by a receiver for landmarks on a map are compared to their known positions. This is a standard test that is often used to compare the accuracy of multiple GPS receivers simultaneously. When the S/A feature was still enabled, the accuracy of the SPS signal served as the baseline for positioning accuracy for commercial GPS rece...

The development tools available for GPS application design vary depending on the complexity of the target system and the GPS solution being used. Most  GPS tracker  vendors offer software tool suites that allow a developer to communicate with the GPS receiver through the serial port of a personal computer. These software tools typically use messages compatible with the standard NMEA (National Marine Electronic Association) format, but many vendors also offer their own customized sets of messages and message formats.  The more advanced development tools, available for some GPS chip sets, are intended to help the application developer integrate their software with the GPS tracking software running on the same MCU. Because of the hard real-time constraints typical of GPS software implementations, the most efficient way to enable the smooth integration of the  GPS tracking platform  with the application software is through a clearly defined software API. With a sta...

When access to the GPS first became available for military and commercial use, only a few companies had the technology and expertise to develop reliable, accurate  GPS Tracking Device  . Application developers who needed GPS services would simply purchase a board level solution from a GPS supplier, and integrate it into their design. In the past, GPS correlators were designed with a single channel, which was multiplexed between each SV signal being received. This resulted in a very slow process for calculating a position solution. Today, systems come with up to 12 channels, allowing the correlator to process multiple SV signals in parallel, achieving a position solution in a fraction of the time. Also, while the correlator functionality is sometimes performed in software using a high-performance digital signal processor (DSP), the real-time processing requirements and repetitive high rate signals involved make a hardware correlator solution ideal, from both a cost and through...

In order to design and build a GPS receiver, the developer must understand the basic functional blocks that comprise the device, and the underlying hardware and software necessary to implement the desired capabilities. The sections below describe the main functional blocks of a GPS receiver, and the types of solutions that are either available today or in development to provide that functionality. The demand for the integration of positioning technology into smaller devices is challenging antenna development. The industry is already pushing for smaller antennas for applications such as a wristwatch with integrated GPS, which is smaller than most patch antennas available today. Another demand is for dual-purpose antennas that do double duty in wireless communication devices, such as in a mobile telephone with an integrated GPS receiver. Inevitably, the future will bring smaller and more flexible antennas for  GPS Tracking Device  . The function of the downconverter is to s...

While most  GPS Tracking Device  have the same functionality, there are a lot of differences in manufacturer and model user interfaces. In a way it’s like sitting someone down in front of three personal computers, one running Microsoft Windows XP, one running Linux (with the KDE or Gnome interface), and the other a Macintosh, and asking a computer novice volunteer to perform an identical set of tasks on each of the computers. Good luck! Because of this, you’re not going to find detailed instructions on how to use specific GPS receiver models. What you will find is information on how to use most any GPS receiver, with some kindly suggestions tossed in when it’s appropriate to consult your user’s guide for details. GPS receiver models are constantly changing and being updated. Instead of recommending that you buy a certain brand or model (that could possibly be replaced by something cheaper and better over the course of a few months), I’ll tell you what questions to ask whe...

GPS receivers are composed of three primary components: the antenna, which receives the radio frequency (RF) broadcasts from the satellites; the downconverter, which converts the RF signal into an intermediate frequency (IF) signal; and the baseband processor or correlator, which uses the IF signal to acquire, track, and receive the navigation message broadcast from each SV in view of the receiver. In most systems, the output of the correlator is then processed by a microprocessor (MPU) or microcontroller (MCU), which converts the raw data output from the correlator into the positioning information which can be understood by a user or another application. The sections below provide an overview of the three key components of a GPS receiver, describing in generic terms the functionality and capabilities typically found in these systems. As the capabilities of the MPU or MCU needed to process the correlator output is largely dependent on the needs of the applications and the particular...

Additional techniques are being developed for increasing the accuracy of the positioning information derived from the GPS for certain applications. One technique, which has been developed by the US Federal Aviation Administration (FAA), uses transmissions from communication satellites to improve the positioning accuracy of GPS tracking device in aircraft. This technique, known as the wide area augmentation system (WAAS), uses a network of wide area ground reference stations (WRS) and two wide area master stations (WMS) to calculate pseudorange correction factors for each SV, as well as to monitor the operational health of each SV. This information is uplinked to communication satellites in geostationary earth orbit (GEO), which transmit the information on the L1 frequency, along with additional ranging signals. This system has improved the positioning accuracy of GPS on board aircraft to within 7 metres horizontally and vertically, allowing the system to be used by aircraft for Catego...

Enhanced client-assisted GPS positioning The enhanced client-assisted GPS positioning technique is a hybrid between autonomous GPS and server-assisted GPS. This type of solution is similar to the serverassisted GPS, with the location server providing the mobile unit with a list of visible satellites on demand. However, in an enhanced client-assisted system, the mobile unit does the complete PVT calculation rather than sending pseudorange information back to the location server. This technique essentially requires the same processing power and capabilities as an autonomous  GPS solution , in addition to a communication link between the mobile unit and the location server. However, the amount of time required to complete the PVT calculation is much less than with an autonomous GPS solution, because of the satellite view information provided by the location server, and fewer exchanges with the location server are required than with a server-assisted solution. Dead reckoning ...

Server-assisted GPS positioning Server-assisted GPS is a positioning technique that can be used to achieve highly accurate positioning in obstructed environments. This technique requires a special infrastructure that includes a location server, a reference receiver in the mobile unit, and a two-way communication link between the two, and is best suited for applications where location information needs to be available on demand, or only on an infrequent basis, and the processing power available in the mobile unit for calculating position is minimal. In a server-assisted GPS system, the location server transmits satellite information to the mobile unit, providing the reference receiver with a list of satellites that are currently in view. The mobile unit uses this satellite view information to collect a snapshot of transmitted data from the relevant satellites, and from this calculates the pseudorange information. This effectively eliminates the time and processing power require...