The use of GPS provides one of the best means we currently have for preserving the locations of old abandoned graveyards.
WHAT IS IT?The Global Positioning System (GPS) is a satellite-based navigation system made up of a network of 24 satellites placed into orbit by the U.S. Department of Defense, orbiting the earth about 12,000 miles above us. They are constantly moving, making two complete orbits in less than 24 hours. These satellites are travelling at speeds of roughly 7,000 miles an hour. GPS satellites are powered by solar energy. They have backup batteries onboard to keep them running in the event of a solar eclipse, when there's no solar power. Small rocket boosters on each satellite keep them flying in the correct path. The satellite orbits are calculated to provide continuous global coverage; with all 24 satellites in operation, the necessary four satellites are in view of a GPS receiver 100% of the time. On average, eight satellites are present above the horizon at any given time.
Because GPS satellites can break down and their orbits are subject to drift, the Global Positioning System also includes a set of ground stations around the earth that monitor the satellites' operation and location. The ground stations relay information to a master ground station, which then sends updated information back to the satellites so that they can send more accurate signals to GPS receivers on earth.
GPS works in any weather conditions, anywhere in the world, 24 hours a day. The full constellation of 24 satellites was achieved in 1994. Each satellite weighs approximately 2,000 pounds and is about 17 feet across with the solar panels extended. transmitted power is less than 50 watts and they are built to last about 10 years. Replacements are constantly being built and launched into orbit. There are no subscription fees or setup charges to use GPS.The following websites offer
- GPS Primer
An excellent illustrated resource about GPS. Includes nine pages of content plus images, from the Aerospace Corporation.
- US Naval Observatory
- Global Positioning System Overview
A very thorough overview of GPS.
THE HISTORY OF GPS
The United States Department of Defense began work on the current GPS system early in the 1970's, when satellite technology made it feasible to provide the military with continous global coverage. The first GPS satellite was launched in 1978, and the system was declared fully operational in July of 1995. ln the 1980s, the government made the system available for civilian use. GPS works in any weather conditions, anywhere in the world, 24 hours a day.
In 1996 the National Security Council published the following goals for the GPS system:
- To strengthen and maintain national security.
- To encourage acceptance and integration of GPS into peaceful civil, commercial and scientific applications worldwide.
- To encourage private sector investment in and use of U.S. GPS technologies and services.
- To promote safety and efficiency in transportation and other fields.
- To promote international cooperation in using GPS for peaceful purposes.
- To advance U.S. scientific and technical capabilities.
On March 29, 1996, a Presidential Decision Directive (PDD) was signed by President Clinton that described GPS as an international information utility. The PDD included the following directives:
- The U.S. government will continue to operate, maintain and provide basic GPS signals worldwide, free of direct user fees.
- The U.S. will advocate the acceptance of GPS and it's augmentations as a standard for use by initiating international discussions and agreement with Japan and Europe.
The United States government permits worldwide, continuous access to GPS signals, free of charge. And, since the GPS system became operational in 1995, the development of "civil, commercial and scientific applications" has proceeded at breakneck speed. The development of these applications in 2000 and beyond will be particularly exciting because the United States government has abandoned its policy of "Selective Availability." Under this policy, civilian users of GPS could only pinpoint their location to within about 100 meters (330 feet). As of May, 2000, however, civilian users can obtain the same accuracy as military GPS users. This means that all GPS applications will be able to pinpoint a location to within 20 meters (66 feet).
A full history of the GPS system can be found at the GPS History, Chronology & Budgets website located at http://www.rand.org/publications/MR/MR614/MR614.appb.pdf (PDF)
HOW GPS OPERATES
GPS satellites circle the earth twice a day in a very precise orbit and transmit signal information to earth. GPS receivers take this information and use triangulation to calculate the user's exact location by the use of longitude and latitude information. Essentially, the GPS receiver compares the time a signal was transmitted by a satellite with the time it was received. The time difference tells the GPS receiver how far away the satellite is. Now, with measurements from a few more satellites, the receiver can determine the user's position and display it on the unit's electronic map. Today's GPS receivers are extremely accurate, and they maintain strong locks, even in dense foliage or urban settings with tall buildings. Certain atmospheric factors and other sources of error can affect the accuracy of GPS receivers. GARMIN GPS receivers are accurate to within 15 meters on average. It should also be noted that the military places a random error in the signals so that civilian units are not as exact in pinpointing locations as the military units.
Latitude is measured as distance from the equator, given in degrees. Think of these latitude degrees or lines as "tomato slices" of the globe. The equator is assigned the value of 0o (read as "zero degrees") latitude. The north pole is assigned the value of 90o North latitude while the south pole sits at 90o South latitude. These north and south pole values establish the extreme limits of latitude.
Latitude has been used in establishing U.S. state boundaries. For example, the line that forms the southern border of Tennessee is the 35o North latitude line, Kansas' northern border is the 40o North latitude line, and Wyoming's northern border is the 45o North latitude line--or half the distance between the equator and the north pole.
North latitude is also commonly referred to with a positive value while latitudes south of the equator are often referred with a negative value. Thus the city of New Orleans, Louisiana, could be approximated at 30o North latitude or simply + 30o latitude while the city of Durban in South Africa far south of the equator could be approximated at 30o South latitude or simply -30o latitude.
Longitude is measured as distance east or west from an imaginary line drawn from the north pole to the south through Greenwich, England (the home of the person who made up the system of longitude), given in degrees. Think of these degrees or lines like "orange quarters" of the globe. There are 180o (read as "one hundred eighty degrees") in either direction--east or west--of the line through Greenwich. At 180o the east and west longitude lines merge in the Pacific Ocean, forming another well-known line called the international date line.
Longitude lines have also been used in establishing U.S. state boundaries. For example, the western border of Nevada north of Carson City is the 120o West longitude line. The 94o West longitude line cuts right through Daviess County so all longitudes in the county will be very close to 94o West longitude.
Like latitude, longitude can be referred to with a positive or negative value instead of east or west. If longitude is positive, it is a place east of Greenwich; if longitude is negative, it is a place west of Greenwich. Therefore, all longitudes in the U.S. are west, or negative, longitudes.
By converging a latitude line (a horizonal line) with a longitude line (a vertical line), a unique and precise spot on the globe is located. Both latitudes and longitudes are further broken down into minutes and seconds. Each degree has from 0 to a maximum of 59 minutes and each minute has from 0 to a maximum of 59 seconds.
Some use UTM (Universal Transverse Mercator) readings which is a grid coordinate system that gives you a position in specific zones. The GPS Device is a machine that sends and receives signals to and from the satellites in an effort to determine your current position. GPS devices were long used by boats and airplanes, but the technology has become so affordable, that consumers can now buy them for personal use.
For Additional Information, please visit the following online GPS Tutorials:
- All About GPS
An animated tutorial on the basics of GPS from Trimble Navigation. The site also includes information on how Differential GPS works and the application of GPS to free flight avionics navigation.
The application of the GPS to a cemetery appears to be somewhat unique, though it differs very little from other consumer applications. By using a GPS device, you can stand in the middle of a cemetery, and it will determine the latitude and longitude coordinates, and even altitude if it has enough satellites tracked. It can store up to 500 locations in memory so that you can refer back to it later on.
A sample listing for the Crosier Cemetery located in South Harbor, Minnesota would look like this:
Global Positioning System (GPS) Latitude/Longitude:
46.07889 / -93.65333
A good example of the use of determining the boundaries of a cemetery can be found at the Jewish Cemetery in Rozhnyatov website located at:
Additional information on this subject can be found at:
- Using A GPS Device
Steve Paul Johnson
- Lost? Get A GPS
Elizabeth Kelley Kerstens, CGRS
- The Global Positioning System: Assessing National Policies