Introduction to GPS Take a couple of seconds if you will and think of how hard it must have been for our ancestors to travel from place to place. Back in the days before street signs could direct them and streets were almost not even there. Imagine the time when they could not call AAA for journey planning and they were not even always certain which direction to travel in order to reach a destination. How do you think they traveled from point A to point B? They learned that in several ways. They used the stars to direct their way, they put up landmarks to leave track of wherever they had been, they drew maps and oftentimes just roamed about until they arrived wherever they believed they wanted to be. Nowadays, we have it a great deal easier. Not only do we have the advantage of elaborated maps, street names, house names and much more, but we In addition have advanced navigation devices which can assist us along our way in the form of Global Positioning System (GPS). GPSs have revolutionized the way we travel. Formerly, the family holiday meant Dad driving the car and Mom reading a paper map all the while reasoning about the most effective route to take. Technology has progressed a long way and GPS definitely has made a difference in how and even where we travel. It was initially created by the Defense Department for military uses but before long, enterprising firms recognized that this technology could have some really great applications for the day-to-day person and they convinced the government to permit the technology to be brought out for distribution to the general public. At present, average people, with the assistance of a GPS receiver, are able to do much with a GPS system including navigating their way on journeys and even tracking vehicles. The Global Positioning System technology can do so many things that it can be mind boggling and it could help to know how a GPS operates and how it can aid you. The applications are altering almost on a day-to-day basis as the technology develops and grows. In this website, we will try to explain GPS to you, how it functions and how it can work for you. Follow us through the technical stuff and you might be amazed at what you find out! How Does A GPS Operate When people discuss "a GPS," they typically mean a GPS receiver. The Global Positioning System (GPS) is in reality a constellation of twenty-seven Earth-orbiting satellites (twenty-four in operation and three extras just in case one fails). The United States military developed and implemented this satellite network as a military piloting system, but before long opened it up to everyone else. Each one of these three thousand- to four thousand-pound solar-powered satellites circulates the globe at around twelve thousand miles (19300 km), making two full rotations daily. The orbits are arranged so that during any time, anyplace on Earth, there are at minimum four satellites "visible" in the sky. A GPS receiver's task is to locate four or more of these satellites, work out the distance to each one, and apply this information to deduct its own position. This procedure is based on a simple mathematical rule known as trilateration. Trilateration in three-dimensional space could be a bit tricky, so we will begin with an explanation of simple two-dimensional trilateration. Suppose you're somewhere in the U.S. and you are completely lost -- for some reason, you have perfectly no hint where you are. You see a friendly local and ask, "Where in the world am I?" He replies, "You’re six hundred and twenty-five miles from Boise, Idaho." This is a good, true fact; however it is not particularly useful by itself. You could be anywhere on a circle around Boise which has a radius of six hundred and twenty-five miles. You ask another local where you are, and she replies, "you're six hundred and ninety miles from Minneapolis, Minnesota.” Now you are getting somewhere. When you combine this information with the Boise information, you've two circles which intersect. You therefore know that you must be at one of these two points of intersection, if you're six hundred and twenty-five miles from Boise and six hundred and ninety miles from Minneapolis. When a third local tells you that you are six hundred and fifteen miles from Tucson, Arizona, you will be able to eliminate one of the possibilities, since the third circle will only intersect with one of these points. You straightaway know precisely where you are – Denver, Colorado. This similar concept works in three-dimensional space, likewise, but you are dealing with spheres rather than circles. Basically, three-dimensional trilateration Is not much different from two-dimensional trilateration, only it is a bit trickier to visualize. Try to visualize the radii from the earlier examples going off in all directions. So rather than a series of circles, you obtain a series of spheres. How Much Does A GPS Cost There are so many firms that have caught on the “GPS Train” that it could be overwhelming to attempt and work out which one you would like to purchase for yourself. Naturally, one of the greatest considerations you'll want to think of is what you plan to use your GPS system for. We’ll try to go over some of the most well-known products from a few of the most popular manufacturers. Please remember that we do not condone one particular product over the other and we'll try to remain fair in our descriptions taking them from a few of the places that have done reviews of these products. Among the most familiar names in the GPS business is Garmin. Garmin has been developing GPS systems for a long time, and they are remaining top of technology to continually turn out new systems that stay on the top picks of reviewers all over. Reviewers say that the Garmin GPS 60CSx hand-held device is the most dependable all-around hand-held GPS and it receives great scores in reviews for fast map delivering and rapid satellite lock even from a cold start. This is because of its SiRF Star III chipset which is among the most innovative technology around now. This hand-held GPS is rubberized and water-impermeable and comes with a 64MB memory card so you will be able to add extra maps. It comes pre-loaded with North American base maps however reviewers state this unit actually shines when used with the optional Garmin MapSource software. The Garmin GPS 60CSx has got a 2.6 inch color display screen, one electronic compass, and one barometric altimeter, along with an extraordinary geo-caching menu (which we have already discussed before!) It weighs a light seven and half ounces and runs for almost eighteen hours on two AA batteries. Although the Garmin GPS 60CSx is surely among the best hand-held devices around according to reviewers, this type of technology are quite expensive. An estimated price for a unit like this runs in the $400 range, but don’t forget, you're paying for quality and that you'll certainly receive! Military Uses Of GPS With concern to military practical application, GPS permits precise aiming of various military weapons including ICBMs, the cruise missiles, and precision-guided weaponries. It's used to pilot and organize the movement of troops and supplies. The GPS satellites likewise carry nuclear detonation sensors which form a major part of the U.S. Nuclear Detonation Detection System. Precise and up-to-date information on the position of the opposition as well as the military's own army is among the most vital information a military commander looks for. In today’s fast paced electronic battleground such information, if propagated well-timed, can play a major force multiplier. The dawn of the space age has resulted in the evolution of various dual use technologies, which find far-reaching application both in military and civilian fields. Global Positioning System (GPS) is among such technology. Military forces all over the world are employing GPS for various applications both during wartime and peacetime. These include piloting, aiming, rescue operation, guidance of forces and facility management. With war clouds hovering everywhere, the US Government led army is expected to showcase arms, which rely to a great extent on GPS for their accuracy and lethality. Mankind have all of the time looked towards the skies for navigation. Even now heavenly bodies like sun and stars are used for determining the directions. This takes on more importance if you are a soldier moving in strange enemy territory. The importance of locating one’s location in the world cannot be greater than for a soldier, since this could mean the difference between life and death, defeat and triumph. With the arrival of the space age, man has tried to replace these heavenly bodies with artificial orbiters so that piloting is possible both during daytime and nighttime. Global Positioning System (GPS) is one such multiple use technology, which has found far-reaching application both for military and civilian purposes in area of navigation and others. GPS has afforded military forces the deadly combination of precision strike with unfavorable weather performance, standoff area, and functional flexibility - all at a low marginal price. There are actually four things that are highly important in a GPS system that the military requires: precision, all-weather applicable, ease of use, and movable. The GPS system presently in service meets these necessities completely. GPS Maps Almost all GPS receivers come furnished with pre-loaded maps. But, these maps are not always what you require and/or require. That's why you'll prefer to look into resources that will give you additional maps. And there are a whole lot of ways to get extra maps for your GPS. The most basic function of a GPS receiver is to receive the transmissions from at least four satellites and combine the information in those transmissions with information in an electronic almanac, all in order to work out the receiver's location on Earth. As soon as the receiver makes this computation, it will tell you the latitude, the longitude and the altitude (or some similar measurement) of its present position. To make the navigation easier, almost all receivers plug this raw information into map files stored in memory. You may use maps stored in the receiver's memory, connect the receiver to a computer that can keep more elaborate maps in its memory, or just purchase a detailed map of your area and determine your way using the receiver's latitude and longitude readouts. Certain receivers allow you to download detailed maps into memory or supply detailed maps with plug-in map cartridges. A standard GPS receiver will not just position you on a map at any specific location, but will In addition trace your path across a map as you travel. If you keep your receiver on, it could stay in continous communication with GPS satellites to determine how your location is changing. With this data and its built-in clock, the receiver can provide you several pieces of valuable and useful information: • How far you have traveled (odometer) • How long you have been traveling • How fast you are moving (speedometer) • What your average speed is • A "bread crumb" trail displaying exactly where you’ve traveled on the map • The approximate time of arrival at your destination if you uphold your present speed That's why having a large number of maps at your disposal is such an important tool for making your GPS receiver do what you're wanting it to do. When you carry a GPS, you can be guaranteed that you will be able to get from point A to point B with little or no problem. Almost all of the modern GPS systems carry voice capabilities that can give you with verbal directions that allow you to focus on your driving. GPS Background GPS innovation is established partly on ground-based radio navigation systems that evolved in the early forties and these were employed in the Second World War. These systems were called LORAN and Decca Navigator and concentrated on learning about where the opposition was so that they can either assault or back out depending on the size of the army. Further inspiration for modern Global Positioning System came up when Sputnik was launched by the Soviet Union in 1957. A team of scientists watched Sputnik’s radio transmissions and noticed that due to Doppler Effect, the frequency of the signal getting transmitted was high as the satellite came near and lower as it moved away. The Doppler shift is the alteration in frequency and wave length of a wave as it is seen by an observer moving relative to the source of the waves. This team of scientists that was researching Sputnik’s radio transmissions shortly understood that as they knew their exact location on the Earth, they could pin point wherever the satellite was along its orbit by assessing the Doppler shift. This was groundbreaking and very interesting for the armed forces at the time. The US Navy employed the first satellite navigation system known as Transit. It was first successfully tested in 1960 and was rather impressive for everybody in the armed services. When the Navy tried out Transit, they did so hoping for some rather specific results. Using a configuration of 5 satellites, they discovered that the arrangement could give a navigational fix roughly once per 60 minutes. In 1967 the Navy created the Timation satellite which showed the ability to place precise clocks in space. This is a technology that the Global Positioning System or GPS relies on. In the seventies, the land-based Omega Navigation System, established on signal phase comparison, became the first global radio navigation system. In February of 1978 the first experimental Block-I Global Positioning System satellite was launched into space and the evolution of modern GPS systems started. These original satellites were at first built by Rockwell International. Nowadays, the satellites we use for GPS are made by Lockheed Martin. In 1983 Soviet interceptor aircraft shot down a civil airliner flight KAL 007 while it flew in bounded Soviet air space. This monstrous act killed all 269 people on board – every one of whom were civilians. Not long thenceforth, President Ronald Wilson Reagan declared that the Global Positioning System should be made available for civilian use as soon as it was completed. Due to this horrifying act on the part of the Soviets, development of the GPS system was intensified much more than it ever had been before and experiments started earnestly. By mid eighties, 10 more experimental Block-I satellites had been launched into space to verify and validate the concept of Global Positioning System and in 1989; the first modernistic Block-II satellite was launched. By end of 1993, the GPS system accomplished initial functional capability and just a month afterward, a full constellation of twenty-four satellites were in orbit with fully functional capability announced by NAVSTAR in April of 1995. A year later, President Clinton recognized the importance of Global Positioning System to civilian users in addition to military users which motivated him to issue a policy directing that GPS to be a dual-use system meaning civilian and military. He founded an Interagency Global Positioning System Executive Board that was accountable for managing GPS as an asset of the U.S.A Solutions Of Inaccuracy In GPS Electronics errors are among various accuracy-degrading effects. They include ionospheric effect, ephemeris effects, satellite time errors, multi-path shift, tropospheric effect, and numeric errors. Inconsistencies of weather conditions affect the speed of the GPS signals as they pass across the Earth’s atmosphere and ionosphere. Fixing these errors is a considerable challenge to improving GPS position accuracy. These errors are smallest when the satellite is directly overhead and become bigger for satellites closer to the horizon because the signal is affected for a longer time. As soon as the receiver’s approximate location is identified, a mathematical model could be applied to estimate and correct for these errors. Since ionospheric delay affects the speed of microwave signals in a different manner based on frequency – a characteristic called dispersion – both frequency bands could be employed to assist in reducing this error. A few military and costly survey-grade civilian receivers compare the different delay in the frequencies to assess atmosphere dispersion and apply a more accurate correction. This could be done in civilian GPS receivers without deciphering the P(Y) signal carried on L2 by tracking the carrier wave rather than the modulated code. To achieve this on lower cost receivers, a new civilian code signal on L2 known as L2C was added to the satellites. This new signal allows for a direct comparison of the L1 and L2 signals using the ciphered signal rather than the carrier wave. The effects of the ionosphere usually change slowly and could be averaged over time. The effects for any specific geographical region could be easily calculated by comparing the GPS-measured location to a known surveyed location. This rectification is also valid for other receivers in the same general position. A lot of systems send these information over radio or other links to allow L1 only receivers to make corrections. The date is transmitted through satellite system and transmits it on the GPS frequency using a special pseudo-random number so only a single antenna and receiver is necessary. In addition, Humidity causes a variable delay resulting in errors like the ionospheric delay but occurring in the troposphere. This effect is localized to a greater extent and alters more rapidly than ionospheric effects and is not frequency dependent. These characters make it a great deal more difficult to make accurate measurement and compensation for humidity errors than with the ionospheric effects. Shifts in altitude likewise change the amount of delay because of the signal passing across less of the atmosphere at higher elevations. Since the GPS receiver calculates its approximate altitude, this error is comparatively simple to correct. GPS signals could also be affected by multi-path issues where the radio signals reflect off of surrounding terrain like buildings and hard ground. These delayed signals could cause inaccuracy as well. Choosing The Right GPS With all of the different alternatives you have in GPS receivers that are on the market nowadays, you might feel a bit overwhelmed in deciding which one you wish to buy. While you'll want something which can meet your needs, you may wish some features that you don’t even know exists, so we will assist and guide you along the way when it comes to knowing what to search for in a GPS receiver. These suggestions come in no specific order; however they're things that you'll have to consider when picking out a GPS. Each part of your GPS system will work together to present you the options that you're looking for and the performance that you require. First of all, take a look at the display. Seek color displays which are comfortable to see in all lighting situations, like the one found on the Lowrance iWay 500c. Choose a GPS model with a good color screen which could be read in all lighting conditions. The larger the screen the costlier the unit will be, however even large screens could be hard to read in direct sunlight. In addition, check the viewing performance of the display to ensure that you are able to read it from any angle. Seek a model which includes street-level mappings. Some producers charge extra to unlock maps from their sites or CDs, while others include only partial areas. This can get costly if you are planning a cross-country journey. Be sure you are able to update the unit's firmware and mapping information. On almost all portable models, a USB or serial port allows you to connect the system to a personal computer, where you will be able to upload the up-to-date maps and system software as it becomes available. On certain models known as in-dash models, maps are generally read from an incorporated DVD or CD player and needs just the latest discs to be brought to-date. Select a GPS unit to conform to your journeying habits. If you do many long-distance driving, look for a model with a dedicated hard drive which stores maps of the whole country. Alternatively, a model which uses an SD card to store maps is a good bet, and you will be able to purchase more cards to load more maps when required. If you would like to share one unit between more than one vehicles, select a model that is light and easy to install and remove from your vehicle. Stay away from permanent mounting devices unless you plan on using the unit in only one vehicle.