GPS (Global Position System):

 The GPS (Global Positioning System) is a "constellation" of 24 well-spaced satellites that orbit the Earth and make it possible for people with ground receivers to pinpoint their geographic location. The location accuracy is anywhere from 100 to 10 meters for most equipment. Accuracy can be pinpointed to within one (1) meter with special military-approved equipment. GPS equipment is widely used in science and has now become sufficiently low-cost so that almost anyone can own a GPS receiver.

 The GPS is owned and operated by the U.S. Department of Defense but is available for general use around the world. Briefly, here`s how it works:

• 21 GPS satellites and three spare satellites are in orbit at 10,600 miles above the Earth. The satellites are spaced so that from any point on Earth, four satellites will be above the horizon.
• Each satellite contains a computer, an atomic clock, and a radio. With an understanding of its own orbit and the clock, it continually broadcasts its changing position and time. (Once a day, each satellite checks its own sense of time and position with a ground station and makes any minor correction.)
• On the ground, any GPS receiver contains a computer that "triangulates" its own position by getting bearings from three of the four satellites. The result is provided in the form of a geographic position – longitude and latitude – to, for most receivers, within 100 meters.
• If the receiver is also equipped with a display screen that shows a map, the position can be shown on the map.
• If a fourth satellite can be received, the receiver/computer can figure out the altitude as well as the geographic position.
• If you are moving, your receiver may also be able to calculate your speed and direction of travel and give you estimated times of arrival to specified destinations.

 The GPS is being used in science to provide data that has never been available before in the quantity and degree of accuracy that the GPS makes possible. Scientists are using the GPS to measure the movement of the arctic ice sheets, the Earth‘s tectonic plates, and volcanic activity.

 GPS receivers are becoming consumer products. ln addition to their outdoor use (hiking, cross-country skiing, ballooning, flying, and sailing), receivers can be used in cars to relate the driver's location with traffic and weather information.

GPS & Navigation: 

 If you are in a storm the maps and compass could not help as it is difficult to determine your actual position but GPS tracking system can help you get back home. Get GPS devices and never loose your way! 

Put away your compass and your maps, a GPS tracking system will take care of all your navigation needs. A GPS system is the most effective navigation tool on the market today. Using satellite systems around the world, GPS navigation system is able to locate your exact position in the world, no matter where you are.

GPS is a satellite-based radio-navigation system that was developed and operated by the U.S. Department of Defence. GPS allows land, sea, and airborne users to determine their position, velocity, and time 24 hours a day, in all weather, anywhere in the world with a precision and accuracy far better than other systems available today or in the foreseeable future.

GPS has become a widely used program used for map-making, commerce, land surveying, hunting, and scientific research. Not only is it used for civilian purposes, it is also used for military and naval exercises. Most importantly, what is trusted by the military and navy is now available to the average person. 

A GPS receiver calculates its position by measuring the distance between itself and three or more GPS satellites. By measuring the time delay between transmission and reception of each GPS microwave signal, the GPS calculates the distance based on the time delay.

GPS receivers come in a variety of formats and, due to the increase in technological advancements GPS can be integrated into cars, phones, and even watches. GPS systems have become easy to use and easy to care. Thus people all across the world are taking the time to understand the benefits the GPS navigation system.

With GPS devices you will never loose your way but GPS devices are also beneficial in farming, balloon tracking, cell phone tracking, roadside assistance, hunting, etc. So get a GPS navigation system and discover the world!   " Paul Matthew"

GPS Antenna:

 GPS Antenna is an important part of the user facility: GPS receiver gets satellite signals and related data through an antenna; the baseline and three-dimensional coordinates vector GPS obtained which used for geodetic measurements, is the result of the coordinate vector between the centers of GPS antenna, plus the antenna height, then after corresponding correction. For the characteristics of the GPS antenna itself, there is inconsistent between geometric center and the electrical phase center. Not only in three directions of the east, north, elevation being a fixed bias, and changes with the altitude and azimuth of GPS satellite receiver. Sometimes this change will bring in a dozens centimeters of error in the elevation direction of, if leave out to be amended, will impact on the measurement results, especially in the high-precision GPS measurements.

 While using GPS for static measurements, conducts short baseline or ultrashort baseline static measurements with the same type of antenna, the GPS antenna in the both ends of the baseline can receive the same number of satellites and signal strength(assuming no environmental interference stations). The electrical phase center of GPS antenna at both ends of baseline has the same changes with GPS satellite receives. This situation can be considered a change in the antenna phase center resulted in a small amount of translation of the baseline. But the baseline length and the corresponding three-dimensional coordinates components are unaffected. So in the baseline resolving there is no need to consider corrections with changes in the antenna phase center.

 But when conducting long distance and high-precision measurement with the same type of antenna, the GPS antenna in the both ends of the baseline receives inconsistent satellite, not only the elevation angle, azimuth angle may be different, but the number of the satellites may be different. In this case, corrections with changes in the antenna phase center must be considered when calculating baseline. Carry out high-precision measurement when using of different types of antennas, must consider corrections with the change of antenna phase center.