The Global Positioning System (GPS) consists of 27 satellites that orbit the earth. Using receivers on earth, these satellites are used to obtain a wide variety of information for several applications today. Military usage of this technology were one of the first
The Global Positioning System (GPS) consists of 27 satellites that orbit the earth. Using receivers on earth, these satellites are used to obtain a wide variety of information for several applications today. Military usage of this technology were one of the first fields to take advantage of the benefits of this system. Bringing advancements in tracking, communication, and mapping, the GPS technology allowed the military to ultilize its troops more efficiently. In Civilian usage, this system has allowed drivers to navigate more accurately and efficiently. The GPS technology has also served as tracking devices in monitoring vehicles and people in real time, assisting the police force in decreasing crime and violent activity. This instrument has also been a key tool in measuring tectonic motions in earthquake studies. The size of the earthquake can also be more accurately obtained using the GPS system. Engineering fields have also used this technology to expand their knowledge and resources in field surveying, mapping, structural deformation analysis, data inventory, etc. The GPS technology is a crucial tool in the development and advancement of various fields of study in society today.
GPS-10 Group Members
- Brian Sherman: Responsible for describing the alternatives to GPS and performing the GPS experiment
- Jose Rodriguez: Responsible for describing how the GPS system works and performing the GPS experiment
- Sam Agresta: Responsible for describing the military applications of GPS systems
- Jason Caperilla: Responsible for describing the civilian applications of GPS systems
- Danielle Salmon: Responsible for describing the use of GPS systems in Earthquake Studies
- Tharu George: Responsible for describing the use of GPS systems in Engineering applications and Executive Summary
How GPS Systems Work
The Global Positioning System, better knows as "GPS", is a system of 27 satellites that orbit the earth. There are 24 in operation at any given time and three additional satellites in case one fails. It was the U.S. military developed a network for military navigation purposes. Each satellite rotates over the earth at about 12,000 miles and completes two rotations per day. The GPS receivers here on earth locate as many of these satellites as possible at least three are needed however. Using geometry and the mathematical principal of trilateration it can locate the GPS receiver. This video provides a quick one minute briefing on how GPS works. The video was provided by HowStuffWorks, Inc. http://videos.howstuffworks.com/nasa/2191-how-gps-works-video.htm
This unit is made of mostly a plastic shell with a rubber coating back probably for an increase friction factor when the device is placed down. The screw on back can tightly seal water or moisture out of the electronics inside giving it a resistance to water, but by no means is the device waterproof. There is a screen on the front of the device which is difficult to read if there is not adequate light.
GPS in Earthquake Studies
Global positioning systems are used in many different applications including the analysis of earthquakes to measure tectonic motions during and in between sesimic waves. GPS ground-based receivers allows signals to be detected and used in order to determine the receivers' positions (latitude, longitude, height.) The radio signals are sent at two different L-band frequencies (between 390 and 1550 MHz) comprised of a coded sequence. By comparing the received sequence with the original sequence, scientists can determine how long it takes for the signal to reach the Earth from the satellite. The signal delay is useful in learning about the Ionosphere and the Troposphere, two atmospheric layers that surround the Earth's surface.
Additionally, scientists are currently using GPS systems to measure the size of an earthquake by examining the final amount that a station has been displaced in an event.This is done by examining the total distance that a station has moved in an earthquake by comparing its position prior to the event with its position following the event. It has been concluded that there is a relationship between the amount of displacement caused by an earthquake and its magnitude. It is by using this relationship between slip and magnitude that scientists can measure the relative size of an earthquake using GPS.The global positioning system is not used to measure the actual shaking of the ground because of the way in which the actual data is collected. Data is sampled at a certain rate, called a sample rate, which means that the receiver records the information being sent to it from the satellites at a certain interval of time all day long. As a result, data can be processed and a daily solution is determined, which means that the change in position of the receiver is calculated for one day at a time by combining the data collected throughout the day. The data can also be processed at another solution interval. This is the reason why GPS is not used to directly measure the ground shaking during an earthquake. Seismometers are much better equipped to accurately record that sort of high-frequency motion than GPS. So, earthquake size is determined instead by measuring the final displacement of the stations and using the slip versus magnitude relationship.
GPS systems are also being used to provide early earthquake warnings. Currently in California, geophysicists are developing a new network