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Earthmate GPS PN-20 by DeLorme


Executive Summary

This Wiki Report about Global Positioning Systems (GPS) begins with a short introduction of the GPS and the members of group 5. Following is a brief history of ancient methods of measuring latitude and longitude and how it has led to the development of today's GPS. More in-depth research was completed for the specific pages of the Earthmate GPS PN-20, current applications and future possibilities. The rest of the report consists of disassembling, recording parts, and reassembling the GPS, including step-by-step procedures and notes on the process.

The Wiki Report about the GPS has not only increased knowledge on current methods of surveying and its implications on modern technology and engineering, but also putting together a research report in a group. Furthermore, it has familiarized the group with Wikipedia, a current and fast-growing reference web-page, which may become important in future careers.


The Global Positioning System (GPS) was created by the United States Defense Department in the 1970's by utilizing a satellite orbiting the Earth, which provides reliable positioning, navigation, and timing services available worldwide and free of charge. GPS provides accurate time, velocity and location information regardless of weather, time of day, or where in the world the GPS is being used from. The basic reading displayed on each individual GPS at any moment is the position, including longitude, latitude and elevation, the velocity, including the velocity north, east, and up, along with the time, in universal time coordinated, at any instant. The GPS is generally accurate to 10 meters positioning, 10 centimeters per second velocities, and less than 0.1 microsecond time. The GPS has the level of accuracy mentioned before because there are four satellites, guaranteed, available in space to obtain data from at any given time. Additionally, GPS devices are equipped to give directions from where the individual GPS is located to any other place on earth, regardless of the method of transportation (ie: by land, water or air).

GPS-5 Group Members

  • Jackie Bayer: Responsible for disassembly and reassembly of GPS
  • Leah Courtney: Responsible for features of the GPS and current applications
  • Jeffrey Dowgala: Responsible for disassembly and reassembly of GPS
  • Lauren McNally: Responsible for current applications, brief history and future possibilities
  • Austin Wong: Responsible for current applications, brief history and future possibilities


Navigational techniques date back to the second century AD, when the Greek astronomer Claudius Ptolemy prepared a geographical atlas that included estimations of latitudes and longitudes of major Mediterranean cities. Initially, angles and astronomy were primarily used to calculate the individual latitudes of the Earth. On the other hand, longitude values are more difficult to calculate. It is found by astronomically calculating the difference between the times observed of two celestial events, such as an eclipse. For every hour difference in time of the observation of the celestial events, the difference in longitude is 15 degrees.

Navigation readings have come a far way since astronomical estimations were used to determine longitude and latitude. The GPS began as a U.S. Department of Defense military research project in the 1970's. The original idea put forth by the USDOD was to attach atomic clocks on satellites orbiting the Earth and use the gathered data for navigational purposes. The first set of GPS satellites were launched in 1978, and second-generation satellites were then launched in 1989. By 1995, the satellites were fully functional, and used for military purposes, with limited, less accurate use by common citizens. Because of a 1983 misinterpretation of data, in which case a more accurate GPS may have prevented Soviet interceptors from shooting down a Korean Passenger Plane that mistakenly entered Soviet airspace areas, President Ronald Regan allowed the GPS system to be available worldwide free of charge upon completion. Similarly, in 2004, President George W. Bush issued an updated policy to keep GPS free of direct charges worldwide.

Earthmate GPS PN-20 Pages

Satellites Page

The Satellites Page is the first page to appear when the Earthmate GPS PN-20 is turned on. This page summarizes the locations of the various GPS satellites while orbiting the earth, which the individual GPS's are obtaining data from. These satellites make it possible for the GPS system to obtain its various locational data. In addition, this page includes the current GPS status, the signal strength from the satellites, and the GPS accuracy.

Map Page

The Map Page is only available for use if a 2-D or 3-D fix is obtained. If obtained, the GPS can assemble a map of someone's current location with the available satellite data. An example of usage of this page includes driving a car, if a desired location is indicated. Then, the map can be followed to get to the specified location. A few features include the direction of travel, speed of travel, estimated time of arrival to destination, and where to turn, among others. Another feature of this page is the layering application which allows various maps to be available for any particular location. These maps include topographic data, satellite imagery, color aerial imagery, USGS Quads and high-resolution cities.

Compass Page

The Compass Page is a digitally expressed image of an ordinary hand-held needle floating compass. In contrast to a traditional needle floating compass, the GPS page can instruct the compass to point in the direction of a specific destination, instead of it only pointing North, as it traditionally does. If a specific destination is chosen for this page, the GPS will also include the distance and time until the next turn that needs to be taken while traveling.

Trip Info Page

The Trip Info Page can be used to track various components of each trip from start to finish. The screen is divided into eight sections: coordinates (latitude and longitude), trip odometer, trip moving time, trip stopped time, trip total time, current speed, maximum speed and average speed of the trip. This page may be customized by the user to only display certain sections, depending on what information the user finds to be most important.

Find Page

Lost? The Find Page can be used to search for and locate various positions such as addresses, roads, cities, points of interest, way-points, coordinates and more. There are two ways to search on this page. First, there is the "Find Near Map Center", which can be used to locate destinations surrounding a current location, such as geographic features. Second, there is the "Find By Name", which can be used to locate specific locations, such as an address. This page also has a memory for past searches, which allows places previously searched for to be easily pulled up.

Way-points Page

A way-point is a marked location with specific coordinates. It is possible to mark a current location, or a searched location as a way-point by using the "Mark Button". After individual locations have been marked by the way-point page, it can be customized with a name, coordinates and comments. A symbol may be chosen for the way-point to express what the location represents. Symbols include a cave, church, dining area, house, post office, among others, which may be saved for later use. A list of saved way-points may be pulled up to obtain directions to them from any current location.

Routes Page

Various routes may be mapped out using the Routes Page, which include:

  • From a current GPS location to a way-point
  • From a current GPS location to a Find Search result
  • Between two way-points
  • Between two Find Search results
  • Between a way-point and a Find Search result

Once a route is created, its direction can be followed to reach the desired destination.

Tracks Page

By default, the Earthmate GPS PN-20 records & tracks the travel route taken until the recording of the trip is turned off. That is, a user may use the Tracks page it to retrace his or her steps after any distance into the trip. This feature may be helpful for backtracking when lost. Similarly, these tracks may be saved for future use.

Sun/Moon Page

The Sun/Moon Page is used to gain information about the sunrise and sunset or the moon rise and moon set. The GPS can display the times of these, as well as the moon phase for the current GPS location. The screen for the Sun/Moon Page will also display the current time and date, which allows the user to determine how much time until the next rise or set is supposed to occur.

Tide Page

The Tide Page can be used to display information on high and low tides based on a specific time, date and tide station.

Hunt/Fish Page

Convenient for hunters, the Hunt/Fish Page is used to predict if a certain day may be good or bad for hunting or fishing. This page can also predict the best times to hunt or fish for a current GPS location. It is also possible to pan the map to other locations nearby and see the hunting or fishing conditions for that area as well, which makes it easy to find optimum locations and times for hunting and fishing.

Device Setup Page

The Device Setup Page is used to modify default settings on the Earthmate GPS PN-20. Examples of settings that may be altered are battery type, color scheme, back lighting intensity and color contrast.

Current Applications

Basic Current Applications

In general, GPS's are found in everyday life, including in automobiles, aircrafts and ships. Furthermore, they are currently found in cell phones, watches and personal computers. GPS's are used for navigational, construction, surveying and scientific purposes, among others. For example, geologists use GPS's to measure volcanic expansion and fault line movements. Similarly, geographers use GPS's to define spacial relations between different features along the Earth's surface. Finally, GPS's have aided public officials in reducing the time it takes for ambulances, firefighters and police offers to arrive at emergent scenes.


GeoCaching is easily described as a world wide treasure hunt game using GPS navigation. Geocachers hide little trinkets (caches), along with a log book in waterproof containers in various locations around the world. Typically, the caches are not of high value. Each geocacher uses their GPS to determine the coordinates of where they hide their cache, and then enters the coordinates on the geocaching website. Other geocachers then look up these coordination locations and search them out using their own GPS. Once found, the geocacher logs their findings in the log book and on the geocaching website. The geocacher is then free to leave the object there for the next geocacher to find, or they make take the "treasure" and replace it with another treasure of equal or better vaule. This worldwide game has attracted over 480,000 participants and added a fun twist on to the many uses of GPS systems.


Although the GPS cannot replace the accuracy of hands-on field surveying, the maps available on GPS systems can be helpful in preliminary investigations of a plot of land to be surveyed. Also, once the land is surveyed, the data obtained can be uploaded to GPS systems to increase the accuracy of the land data. More recently the use of GPS in surveying in terms of census data in epidemiological research helps show the behavior and movement of diseases based on different spatial geography. This allows researchers to understand the movement of disease in selected areas with different populations of people.


With the various pages and maps available on the Earthmate GPS PN-20, it can make it virtually impossible to get lost. Whether in a car looking for directions to a specific destination or outdoors hiking to find a specific landmark, the GPS system can help anyone find his or her way.

Military Use

Although the military in most situations would use more advanced systems of GPS than the Earthmate GPS PN-20, the same basic applications can be applied. GPS can be used for more accurate location targeting of missile launches, guiding troops who are traveling in unknown territories or in the dark and to enhance communication between air and ground troops.

911 Assistance

Being able to tell 911 exactly where the caller is in an emergency can be extremely helpful, and in some cases, life saving. For example, this would be especially helpful for anyone injured or in danger out in the middle of woods, where there are no roads or signs to distinguish exact locations. Being able to tell 911 the exact global position allows them to get to each emergency quicker.


Also known as geocoding, geotagging allows for people to add geographical metadata to mediums such as websites, GIS databases, and or images. This process also refers to taking non-coordinate points and creating a specific identification to that point. An example of this would be creating coordinate points for new postal addresses in a new residential development. Geocoding helps municipalities create mapping data, with the help of GIS program, of FEMA flood zoning, building zoning, or planning for new developments.

People Tracking

GPS can be used for locating locations as much as people. GPS devices in cell phones allows for parents to monitor their child’s location even at vehicle speeds. Also this would help elderly individuals as well in case of emergencies such as heart attacks, stroke, or simply just lost. Monitoring criminal offenders using GPS saves on the time and energy for an actual person monitoring these criminals. Police can observe and locate people at a centralized location and monitor more than one individual at one time.

Future Possibilities

Precision Agriculture

A new field that is using GPS technology is for agricultural reasons. Farmers can now use GPS data in their machinery. They can tell based on the machine’s location to use a certain amount of fertilizer for less fertile soil and more water in areas with crops that need more watering. This saves them a lot time not adjusting the machinery and ultimately saves them time by allowing them to tend to more crops.

Additional Signals

There are four new signals that are in the process of being developed and added to the current GPS: three civilian signals, L-2C, L-1C and L-5, and one military line, M-1. These new signals are to help facilitate the growing demand for civilian and military uses in the US. These signals are projected to be fully functional by 2013 but early as 2011 with incentives for contractors.

Competing GIS Systems

Other countries are seeing the unlimited benefit of a GPS system. Other nations have or are in the development of a NAVSTAR GPS like system.

  • European Union: Galileo Positioning System hoping to have operational by 2013
  • Russia: GLONASS is projected to have global coverage by 2009
  • China: COMPASS is currently in its experimental phase and hopes to have 35 satellites upon completion.
  • India: The Indian Regional Navigational Satellite System (IRNSS) will have be under complete control over the navigational system. It is unclear whether this will be incorporated with the Russian development of their system.

Before Disassembly Section

The Earthmate GPS PN-20 was in new condition before the disassembly began. The GPS is composed of many elements, but the device was only disassembled down to about nine main parts. Numerous small resistors and capacitors are on the circuit board, and could not be taken off without destroying the equipment. The nine parts include the battery compartment, two double A batteries, memory card, back cover, internal battery, circuit board, keypad and seal, LCD screen, and front cover. In order for the GPS to work, the CD-ROM maps that come in the package with the device need to be loaded on to the memory card. Since group 5 only had one gigabyte of storage, only a few of the maps were put on the card. After the memory card has been inserted in the GPS, it can be used.

As previously stated, the GPS consists of many electronic elements such as resistors and capacitors. These are configured in such a way to make the device operate. The circuit board is the main component in the GPS, and all parts are connected here. Notably, there is a 2-pin molex connection from the batteries to the circuit board and also a LCD flex from the screen to the circuit board, as seen during our disassembly. The user types information into the keypad, which is processed through the circuit board. The data on the memory card is read, and the circuit board sends a signal to the LCD screen after the information has been processed, which shows up for the user to read. The process is powered by the two double A batteries. More detail of the types of materials and how many parts are included can be found in the subsequent sections and photographs.

Disassembly Procedure

The disassembly took place on February 22, 2008 and is outlined below. The only tool used was a small #0 Phillips head screwdriver (typically found in a jeweler's screwdriver kit).

  • 1. Take battery compartment off.
  • 2. Take out the batteries and memory card.
  • 3. Unscrew screws on back cover.
  • 4. Remove cover.
  • 5. Take apart the molex connectors to batteries, internal battery, and sync port.
  • 6. Unscrew screws from circuit board.
  • 7. Remove circuit board from the device.
  • 8. Remove keypad and seal.
  • 9. Snap off screen, but leave LCD flex connected to circuit board.

Most of the disassembly was fairly easy. Steps one and two were especially easy because they need to be done on a regular basis by any user who owns the device. The memory card and batteries need to be replaced often. Taking the screws out was probably the hardest part in the disassembly because they were very tiny, particularly on the circuit board. Removing the wires from certain connections was also pretty easy. The removal of the keypad and seal was tricky because it was easy to tear. Once the screen was taken off, we had to pay special attention not to scratch it or get any marks on it. In general, however, the disassembly was simple.

After Disassembly

Part Table:

Earthmate GPS PN-20 Parts
Part No. Part Name Number of Parts Function Material Image
1 Battery/ Memory Card Cover 1 Protect batteries and memory card Plastic, Rubber
2 Batteries 2 Provide power to the unit Metal
3 Memory Card 1 Provides storage for large maps Plastic, Metal
4 Screws 10 Supports and water resistance Metal
5 Back cover 1 Protection Plastic
6 Circuit Board 1 GPS receiver, processing chip Plastic, Metal
7 Rubber Lining/ Keypad 1 Provides water resistance and a user touch pad Rubber
8 Front Cover 1 Protection Plastic
9 LCD Screen 1 Provides monitor for graphical user interface Plastic, Metal


  • 1. Place the key pad on the back side of the front cover. The key pad should line up in the grooves of the front cover.
  • 2. The circuit board is then placed on top of the key pad inside the front cover making sure the screw holes line up and the LCD screen fits inside its compartment. Double check the lining to be sure it is still aligned in its grooves. (Note: The front cover will have to be lifted up while inserting the circuit board because if the front cover is resting on a surface, then the keys of the keypad will not be able to stick out all the way causing the circuit board not to be inserted correctly.
  • 3. Screw the circuit board screws in. There are only two screws.
  • 4. Plug in the Molex connectors for the double A batteries (3 Pin), the internal battery (2 Pin), and the sync connection (8 Pin).
  • 5. With the lining still in its grooves, place the back cover on making sure the cabling for the batteries on the back cover is inside the back cover and not sticking out into the open area with the batteries and memory card.
  • 6. Screw in the back cover screws. Notice there are rubber rings around certain screws to prevent water penetration into the unit.
  • 7. Place the memory card back in if desired.
  • 8. Insert the double A batteries in their respective positions.
  • 9. Place the battery cover on and tighten the cover with the thumb screws and fold the metal hangers down.

The whole process only involves one tool which is a #0 Phillips head screw driver (typically found in a jeweler's screwdriver kit). During this procedure it is very important that the rubber lining is in its groove before screwing in any screws. If it is not, the unit will be susceptible to water damage if it comes in contact with it. The unit also may not even close properly causing the unit to come apart unexpectedly. The screws should be tightened just enough so that the screws are tight but not so tight that the screws will be stripped when trying to loosen them again. Try not to get any finger prints on the LCD while putting it together. If there are any fingerprints that aren't visible until the unit is turned on, the unit will have to be disassembled again in order to clean it. The LCD screen cannot be taken apart from the circuit board either without force and it will not be easy putting it back together.

After Assembly

After assembly, the unit was turned on and worked just as it did when it first came out of the box. The unit should not be taken apart by just anybody. There are very small and delicate pieces of circuitry inside the unit. If there is an electrostatic building inside the user's body that discharges on the circuitry, it could damage the unit. Also, opening the unit up is voiding some type of warranty which goes for most electronic equipment. If there is a problem with the unit and it is still under warranty, it is wise to just send it back and let the company fix the problem.


[1] Global Positioning System: Serving the World

[2] Geocaching

[3] "Into to GPS"

[4] U.S. Updates GPS Technology

[5] The Global Positioning System: A National Resource