Global Positioning System

The Global Positioning System (GPS) is the only fully functional Global Navigation Satellite System (GNSS). Utilizing a constellation of at least 24 medium Earth orbit satellites that transmit precise microwave signals, the system enables a GPS receiver to determine its location, speed/direction, and time.

Developed by the United States Department of Defense, it is officially named NAVSTAR GPS (Contrary to popular belief, NAVSTAR is not an acronym, but simply a name given by Mr. John Walsh, a key decision maker when it came to the budget for the GPS program[1]). The satellite constellation is managed by the United States Air Force 50th Space Wing. The cost of maintaining the system is approximately US$750 million per year,[2] including the replacement of aging satellites, and research and development. Despite these costs, GPS is free for civilian use as a pub read this entry »

The code tracking loop is used to make pseudorange measurements between the GPS satellites and the GPS receiver.  The receiver’s code tracking loop generates a replica of the C/A-code of the targeted satellite.  The estimated doppler is removed by the phase rotation circuit prior to the correlator.

In order to align the received signal with the internally generated replica, the internally generated code is systematically slewed past the received signal. Typically the output of the correlator is integrated over 1 to 10 ms. If correlation is not detected the phase of the internally generated code is advanced by one chip.  If correlation is not detected after the whole code has been searched the doppler is adjusted and the process repeated until correlation is achieved. Code synchronization is initially maintained by also correlating the received signal with half chip early and late codes. A simple feedback system keeps the prompt (“on time”) code correctly positioned.

To extract the carrier which is still modulated by the navigation message,  the prompt code is subtracted from the incoming signal.  The delay that the receiver must add to the replica code to achieve synchronization (correlation), multiplied by the speed of light, is the pseudorange measurement.  Once the carrier is reconstructed, the center frequency of the replica code is adjusted using Doppler measurements from the carrier tracking loop to achieve a precise frequency lock to the incoming signal, thereby allowing more precise pseudorange measurements. The bandwidth of the code tracking loop is typically 0.1 Hz, which implies that independent measurements are available at approximately 10 s intervals.

GPS needs driver and you can search a driver download on the internet. It might based on windows drivers and you should know about this. Since GPS is mobile thing, you may not need computer drivers but you need mobile GPS for your gadget.

We learn about the nature and scope of regular GPS systems and how the latest Microsoft GPS programs have improved upon this concept for vehicle tracking beyond the earliest felt need of the US Defense Military services – for which they were first developed.

The nature of the GPS device, or the Global Positioning Satellite as it is actually called, is that it is a very advanced navigation system based on satellite communication mad read this entry »

If you are someone who travels a lot because of business or who just enjoys traveling to discover or visit new places that you have not been to before? Then a GPS device is definitely your ultimate travel companion and guide. The US Department of Defense developed this technology and they can be used by anyone, anywhere, and are often used for navigation and are the world’s only fully functional global navigation satellite system (GNSS). read this entry »