This Global Positioning System (GPS) project was done for CAEE-211. Our group looked at the technical and practical uses of the GPS system.
By Alex Craft
Man has navigated the earth since the beginning of his existence thousands of years ago. Simple early land navigation stems from creating orientation reference points, such as: rivers, mountains, and other landscape features. Navigation started out strictly orally conveyed, but as navigation techniques evolved with increasing complexity, orally conveyed navigation would not suffice and thus maps were conceived. Cartographic representations are still prevalent today and helped to lay the foundation for modern navigation techniques, like electronic GPS systems.
"Some centuries ago, it was possible to achieve a determination of your position on Earth which was almost as accurate as with GPS – but only with time, craftsmanship and significantly more complexity." 
More than two centuries ago, it was possible to very accurately pinpoint your position on earth by means of 'satellites'. 
Most ancient navigation techniques were based upon the sun and the stars and were capable of providing very accurate navigation. However, most ancient navigation was founded on a precopernican world.* Ancient Polynesians were one of the first sea-farmers, and thus were one of the first civilizations that learned to navigate by meteorological data. Before famous and distinguished European navigators, the Polynesians had created navigation techniques based purely on the sun and stars.
(*the belief that the earth is at the center of the universe and the sun and the stars thus revolve around the earth)
“Shooting stars” was a way to navigate ones position on earth by determining the degree of longitude and degree of latitude. These coordinates were derived from measuring the angle of the sun or stars relative to the horizon. The history of navigation has seen many devices used to measure the above mentioned angle associated with the horizon. These tools include; the astrolbium beginning in the fourth century, the quadrant beginning in the thirteenth century, the cross-staff beginning in the seventeenth century, and finally the octant and sextant beginning in the eighteenth century.
Time line depicting key contributions in the history of Navigation:
- 13th Century:
- Mariner's compass, invented in Europe
- Dead line; tool for measuring depth of water and topography of bottom ocean
- Portalon Charts; first nautical charts, showed importance to trade routes rather than their actual geographical size
- 14th Century
- Astrolabe (1484) invented by Martin Behaim, to measure the angle above the horizon of the sun and stars to determine latitude
- 15th Century
- Chip Log, crude way to determine the speed of a ship by dragging a line in the water for a given time.
- Mercator Projection (Gerardus Mercator 1569), first accurate representation of the spherical earth
- 17th Century
- Charts of Magnetic Variation (1701), allowed compass to be consistently accurate navigation tool no matter where in the world it was being used.
- Seagoing chronometer (1764), invented by John Harrison, first accurate clock, revolutionized navigation
- 19th Century
- Gyroscopic Compass (1907), invented by Elmer Sperry, first compass to point to true north, unaffected by variation or deviation
- Radar (radio detection and ranging 1935) invented by Robert Watson-Watt, able to locate objects beyond the range of vision by projecting radio waves against them
- Loran (Long Range Navigation 1940’s), hyperbolic navigation system that used radio waves
- GPS (Global Positioning System 1973), created by U.S. Department of Defense, space based radio navigation system.
By Matt Orloff
The GPS system started with the beginning of satellite usage. In 1957, William Guier and George Wiefenbach discovered a method of determining the orbit of Sputnik by using the Doppler alterations in its radio signal frequency that was transmitted. These two researchers were members of the John Hopkins Applied Physics Laboratory in Maryland. A few years later another Hopkins researcher named Frank McClure was looking for a system to let nuclear submarines keep exact coordinates of their location. He simply took the system that Guier and Wiefenbach used and reversed it. Basically, if the submarine could measure a signal from a satellite with a confirmed location, it could then use that and determine its own location.
From this pattern of discoveries in 1964, McClure then influenced a fellow researcher named Kerschner to design a number of satellites whose system would be solely to provide navigational information. There ended up being five satellites. These satellites gave off two types of signals one of which allowed for the signal delays through the ionosphere. The navigation at that point allowed a submarine to get a location accurate to 25 meters in less than ten minutes.
From 1967 to 1971 two other military navigational systems were being experimented with. The navy implemented TIMATION, which used extremely accurate clocks which meant better accuracy on location, but a longer time to establish the coordinates. The Air Force was using a program known as 621B which resisted signal jamming and interestingly enough provided altitude information which was extremely helpful to the Air Force.
Bradford Parkinson was put into the 621B program in 1972. At this time they needed cooperation from the entire military to invest in one single system to eliminate satellites bumping into one another and getting mixed signals. He went before the Department of Defense and tried to get allowance for 621B. The DOD initially said no, but wanted it to be a joint project which ended up being for the better.
Before returning to the DOD for authorization to explore further the three systems were combined with all three of their best attributes. Orbiting prediction came from TRANSIT, the clockwork was taken from TIMATION, and the signal structure came from 621B. The new program (called NAVSTAR) was approved in 1973.
In 1978, the system went online. For the military it was accurate up to 10 meters or about 30 feet. The system was had limited availability to civilians at the time and accuracy was about 50 meters. Surveyors began using this system almost immediately.
Today there are 25 GPS functioning satellites orbiting earth. Statistics show that if an open sky is provided at least six and not more than eleven will give a signal. At first, the military had strict regulations on civilian usage, but after seeing the benefits in allowing non-military usage (particularly in air travel), it became legal and encouraged.
Mechanics of the GPS
By David C. Moncrief
When most people refer to a GPS they are referring to a GPS reciever. This reciever can get signals from three or more sattelites of the 24 GPS sattelites in orbit. 
The sattelites orbit the earth about 12,000 miles (19,300 km) above earths surface. They orbit the earth about twice per day, and are positioned so that at any time at least four sattelites are available for any location on earth.
How location is calculated
A GPS reciever locates at least 4 sattelites and calculates the distance to each. It then uses 3-D Trilateration to calculate it's location.
By intersecting two spheres from the sattelites you create a circle. When you intersect this circle with another sphere from another satellite it creates two points. One of those points is located on earth, which is a sphere itself, which can be used to calculate your location. With each additional sattelite that is used the degree of accuracy increases.
The distance and location of the sattelite are transmittes via low frequency radio waves. These radio waves travel at the speed of light (about 186,000 miles per second, 300,000 km per second in a vacuum). Each sattelite resets it's pattern of signal of pseudo-random code daily. The GPS receiver recognizes these patterns from the different sattelites because it runs the same exact pattern that is reset at the same exact time daily. The delay of the signal is the time it takes for the signal to travel to the GPS reciever. To make this calculation the clocks of the reciever and sattelites have to be precise down to the nano second.
Because each sattelite has an atomic clock on it which costs in excess of $50,000 (US), the reciever can use the signals from each sattelite to calculate the time. By using the sattelites to calculate the time, the reciever can be perfectly synchronized to the sattelites and calculate the travel time of the signal more accurately. The sattelites clocks are also monitored constantly. Because there is less gravity from the earth at 12,000 miles the clocks behave differently. This is partially because the time-space continuim is bent less from the mass of the earth, which leads to time actually occuring at a faster rate in space. Each of the sattelites is monitored by the US military and calibrated constantly with an atomic world clock on earth.
The paths of the sattelites is stored in an almanac in each GPS reciever. Because gravitational pulls from objects such as the sun and moon can affect the orbits of the sattelites, the sattelites send corrections to the recievers along with the time signals.
Because GPS recievers use radio signals that can be affected by the earths atmosphere and objects located on earth, Differential GPS systems are used to correct any large inaacuracies. Radio signals speed varies in the ionospere and troposhere and can be difficult to account for. Differential GPS recievers are in a set location. Because they know their own location and they recieve the signals from the same sattelites as other recievers they can correct any inaccuracies. A lot of Differential GPS send out correction signals for other recievers in the area. 
By Paul Nettleton
Advancements in GPS receiver technology has made it affordable and accurate enough for recreational Land Navigation. Recreational Land Navigation can refer to many activities, but the scope of this paper focuses on hiking, climbing, hunting and fishing, and geocaching.
Outdoor recreational sports, such as hiking, climbing, hunting and fishing, benefit from GPS by providing numerical longitude and latitude coordinates as well as visual mapping. GPS receivers of this sort are usually handheld receivers and come with a wide range of features. When choosing a GPS receiver for land navigation it is important to consider which features are important for your activity. Perhaps the most important feature is that the receiver has a Map screen as opposed to a screen that simply displays your coordinates (longitude and latitude). Map screens usually come in black and white or in color. It is important for hikers to be wary of color screens because many of them are hard to read in direct sunlight (with TransReflective Screens being the exception) ( http://gpsinformation.us/main/gpshiking.htm ). Map screens are desirable because they make it easier to see where you are relative to waypoints. Durability and waterproofness are also important. Because these outdoor activities involve the elements, a GPS handheld receiver should be able to withstand these conditions. Long hikes and endurance climbing can go on for days and battery life can become a concern. Models with a longer battery life are recommended. GPS receivers should also come with build in maps and be able to store many routes (20) and waypoints (500) ( http://gpsinformation.us/main/gpshiking.htm ). Bearing to the next waypoint is crucial for hiking and should therefore be considered a necessary feature. Most of the receivers now are lightweight and small, but for climbing, choosing a GPS receiver based on size could be a factor. A large amount of space for uploading Maps and TopoMaps is a feature which can do wonders for novice to experienced hikers. Antennas and reception is important in densely wooded areas and extreme terrain.
Here’s a fun little video: http://www.youtube.com/watch?v=xo_-DFpDo6A&feature=related
Geocaching is an outdoor treasure-hunting game using a GPS receiver to locate certain “geocaches.” Geocaches are small, waterproof containers containing a small treasure and a logbook. The coordinates of the geocache is posted on a website along with other details. Geocachers can then look up the coordinates and with the aid of a GPS receiver can locate the geocache. The geocachers record their findings in the logbook and online and can take the treasure as long as they leave a treasure of similar to higher value. The official site for geocaching can be found here: http://www.geocaching.com/.
Land Navigation is much easier with the aid of a GPS receiver. GPS receivers can vary from expensive to inexpensive depending on their various features. However, the type and affordability of the receiver will be affected by the type of Land Navigation. For example, Geocaching requires a much simpler and therefore cheaper receiver than hiking. Despite its variability, GPS receiver technology is a source of entertainment which the upper bounds have yet to be reached. If you’re looking into a GPS for recreational Land Navigation, visit http://www.gpslodge.com/archives/cat_handheld_gps_reviews.php for more information.
Use of specific GPS given in class
By Michael Kane
Step 1 - Opening the Packaging
Open all the packaging for the GPS unit and all related accessories and lay all the components on a desk free of clutter. The key components you should make sure you have are the GPS unit, the power adapter for the GPS unit, and the Lithium-Ion battery.
Step 2 - Installing the batteries
Turn the unit over so the screen is facing the table. On the back of the unit are two 'D' rings. Flip those 'D' rings up, unscrew them, and lift off the battery cover. Place the Lithium-Ion battery into the unit, paying close attention the poles of the battery are correct. Plug one end of the power adapter into the GPS unit, and the other end into a 120VAC wall outlet. Let charge for a couple hours
Step 3 - Turning on the GPS unit
Hold the unit so the screen is facing you, the power button is the button with a red graphic in the lower right portion of the unit.
Press and hold this button for approximately 1.5 second. The unit should now turn on, and you should see the satellites page.
Step 4 - acquiring a fix of the current location
Walk outside where you have a clear view of the sky. Turn the unit on. You will notice that once the unit is turned on the satellites page will appear. After waiting a few minutes, you will notice satellites appearing on the screen, and their respective power listed on the bottom of the screen.
After a minimum of four satellites are fixed, the unit will read a position. Press the page button to see where you are on the map screen.
- In/Out - Use to zoom in and out on a map
- Press and hold to zoom all the way in or out on a map
- Press In/Out to scroll page-by-page through a multi-page list.
- Page - Use to cycle through the available pages. The typical page sequence is
- Trip Info
- Route Directions (when available)
- Menu - Give you access to the menu and functions on particular pages.
- Find - Used to search for a point of interest, waypoint, address, coordinate, etc.
- Mark waypoint - Use to mark a waypoint at your current location, assuming you have 4+ fixed satellites.
- Arrow Keypad - Can be used for the follow commands:
- Move the cursor on the map
- Pan the map, by moving the cursor to the edge of the map
- Highlight options on a menu or list. Press and hold to quickly move through a list.
- Highlight character on the on screen keyboard.
- Enter - Can be used for the following functions:
- Select an entry on an on-screen menu,list,button or field
- Get detailed information about the location the cursor is hovering over the map. (If available)
- Quit - Used to cancel actions, or move backwards through a menu tree.
- Power - Used to control do the following functions
- Turn on the unit - press and hold for 1.5 seconds
- Turn off the unit - press then press the enter button when prompted to.
- Change the backlight intensity - press and hold for 3 seconds, with unit already on, and use the arrow pad to change the backlight intensity.
- Turn the backlight off - press and hold until the backlight turns off, with the unit already on.
- Set the unit - press and hold for seven(7) seconds.
Step 6 - Transferring Map data to the Unit
The unit comes shipped with a low detail map covering the entire earth, but the unit is capable of displaying more detailed maps. In order to display these more detailed maps they must be loaded on by you, the user. There are two methods to get detailed maps for your local onto your unit:
- Compatible DeLorme Mapping Software - In the packaging containing your unit, you should have also received the mapping software 'Topo USA 7.0'. Please refer to the directions for that software for details on sending data to your device
- Online Map Cutter - Available at http://data.delorme.com . For detailed information on transferring data to your unit using this method please refer to the 'Online Map Cutter - system help'
Step 7 through ∞ - enjoy you GPS unit
Use your GPS to help you travel through unknown territory, explore areas by geocaching, create routes to travel to new interesting locals.
By Brent Schrader
GPS receivers for car use are similar to handheld units used for camping with a few exceptions. Car receivers are portable just like those used for camping, but they are not ruggedized, meaning car receivers are not water resistant and will not take the same kind of abuse that a GPS receiver designed for outdoor use would. Car receivers also have larger screens and are more likely to have full maps instead of just co-ordinates. The larger screen makes battery life much shorter for car receivers because of this car receivers can be plugged into cigarette lighters. Car receivers also have more features like audio directions, built in MP3 player, local gas prices, weather forecasts, and even local movie times. Car receivers vary largely price. They have a range of $150-$750. The top competitors in this market are currently Garmin and Tom Tom. 
Another option when traveling is the use of Bluetooth GPS for a PDA or laptop computer. Many PDA’s on the market have GPS applications and are capable of many of the feature mentioned previously. Laptops can also use the Bluetooth technology in order to become a GPS receiver. The laptop option is frowned upon by many because it can be a greater distraction while driving and can cause unsafe situations. 
GPS can also be used to track various things such as trucks, objects, and even people. There are numerous fleet tracking devices available. These devices are able to track the location of fleet vehicles, record speed, record stops, and also record mileage. Most devices claim real time updates these updates actually range from five minutes to as short as every ten seconds. Some of these devices have a monthly fee that go along with the service. In 1999 the FCC mandated that all cell phones should be GPS capable. Since then cellular phone companies have been able to assist the police in tracking people if they go missing and instances of that nature. Cellular service providers can also allow parents to track children through cell phones. Verizon Wireless calls this service Chaperone. Through either a website or the “parent chaperone” phone a parent can track the location of there child. Parents can also set up zones where they are notified if a child enters or leaves the predetermined zone. If you are a pet lover then you might want to look into getting a GPS tracking unit for your cat or dog. GPS tracking of pets is very similar to GPS tracking of children. A small modem is attached to the animal’s collar. When the animal leaves a predetermined area the owner gets a message, with the locale of their pet, on their cell phone or computer.
Today GPS can be used to find the quickest way around a traffic jam or to find what time that new movie is playing and of course help you to find your way if you get lost. No more road atlas lying in the back seat or in the trunk. No more trying to figure out how to refold the maps so it can be returned to the glove box. GPS makes navigating to a new place in an automobile easy and fun.