Global Positioning System or GPS refers to arbitrary images of maps, grid, satellites, automobile and handheld navigation devices, or military-slash-secret service gadgets used for investigation. When the use of GPS started, it granted mankind with many applications since people become adapted to Hollywood sci-fi movies that deal with surveillance and high-tech themes.
The United States Department of Defense (DoD) developed the GPS in 1973. GPS functioned to assist soldiers, military vehicles, planes and ships to precisely find out their locations worldwide. The system is composed of 27 solar-powered satellites orbiting over 20,000 kilometers above the earth. From the 27 satellites, 24 are required by the system to cover the entire planet and the remaining 3 satellites serve as back-up in case one fails. The “trilateration” method of GPS acts as receivers on earth wherein 4 satellites are needed. Thus, all satellites are positioned in any way at anytime on earth. The system only requires 4 satellites to be visible in the sky. Ground-based stations receive signals from aerial satellites. With this, satellite motions are being monitored accurately.
Today, commercially available GPS receivers are used as navigation and positioning tools in airplanes, boats, cars, and for outdoor recreational activities. Scientifically, meteorologists use GPS receivers for weather forecasting and global climate studies while geologists used it for earthquake studies. Since 1991, researchers at the Department of Science and Technology’s Philippine Institute of Volcanology and Seismology (DOST-PHIVOLCS) have been using the GPS technology to learn earthquake potentials or active faults in the country. Through the use of millimeter-accurate dual-frequency receivers, Dr. Teresito Bacolcol, Head of the GPS Working Group at DOST-PHIVOLCS, stated that the functions of GPS equipment cover those earthquake measuring devices like strain meter, tilt meter, and those of conventional surveys. GPS receivers have antennas that pick up satellite signals necessary to settle on the coordinates (latitude, longitude and height) of a permanent location. This helps the researchers to spot which areas of these faults are “locked” or are presently storing up elastic strain. Earthquake potential for a locked fault is greater than if the fault were just sliding. GPS technology can predict earthquake.
But dual-frequency GPS receivers are high-priced so the PHIVOLCS GPS Working Group recommend the utilization of the “campaign mode” in determining fault movements. Campaign mode is the occasional occupation and measurement of benchmarks so that a wider area is covered in a lesser cost. PHIVOLCS GPS Working Group has now established around 200 GPS points all over the country and uses 13 dual frequency GPS receivers wherein 8 of which were acquired last year through DOST’s Grants-In-Aid (GIA) budget. DOST had established partnership with various foreign research groups to be able to maintain around 30 nonstop GPS sites established along the Philippine Fault.