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. GPS was originally intended for military applications, but in 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. There are no subscription fees or setup charges to use GPS.
How it works
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. 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 distance measurements from a few more satellites, the receiver can determine the user’s position and display it on the unit’s electronic map.
A GPS receiver must be locked on to the signal of at least three satellites to calculate a 2D position (latitude and longitude) and track movement. With four or more satellites in view, the receiver can determine the user’s 3D position (latitude, longitude and altitude). Once the user’s position has been determined, the GPS unit can calculate other information, such as speed, bearing, track, trip distance, distance to destination, sunrise and sunset time and more.
The GPS satellite system
The 24 satellites that make up the GPS space segment are 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.
Here are some other interesting facts about the GPS satellites (also called NAVSTAR, the official U.S. Department of Defense name for GPS):
The first GPS satellite was launched in 1978.
A full constellation of 24 satellites was achieved in 1994.
Each satellite is built to last about 10 years. Replacements are constantly being built and launched into orbit.
A GPS satellite weighs approximately 2,000 pounds and is about 17 feet across with the solar panels extended.
Transmitter power is only 50 watts or less.
What’s the signal?
GPS satellites transmit two low power radio signals, designated L1 and L2. Civilian GPS uses the L1 frequency of 1575.42 MHz in the UHF band. The signals travel by line of sight, meaning they will pass through clouds, glass and plastic but will not go through most solid objects such as buildings and mountains.
A GPS signal contains three different bits of information — a pseudorandom code, ephemeris data and almanac data. The pseudorandom code is simply an I.D. code that identifies which satellite is transmitting information. You can view this number on your Garmin GPS unit’s satellite page, as it identifies which satellites it’s receiving.
Ephemeris data tells the GPS receiver where each GPS satellite should be at any time throughout the day. Each satellite transmits ephemeris data showing the orbital information for that satellite and for every other satellite in the system.
Almanac data, which is constantly transmitted by each satellite, contains important information about the status of the satellite (healthy or unhealthy), current date and time. This part of the signal is essential for determining a position.
GSM and GPRS Technology
As GSM (Global System for Mobile communications) continues to assert itself as the world’s leading cellular communications technology, the addition of GPRS (General Packet Radio System) has enabled “always on” data connectivity to IP-based systems and opened up a host of new applications.
Hiphen Solutions has a strong track record in GSM and GPRS systems design and satellite network topology which has enabled us to integrate the technologies of GSM, GPRS, GPS, and GIS for the safety of lives and property to all our clients.
GPRS thus facilitates data transfer to our web based secured server platform and home automation which is the ability to remotely access and control in-house appliances and machines.
In addition, GPRS facilitates instant connections to send or receive information immediately as the need arises. No dial-up modem connection is necessary.
|Geographic Information Systems as an Integrating Technology is one of many information technologies that have transformed the ways we conduct research and contribute to society.
GIS have evolved by linking a number of discrete technologies into a whole that is greater than the sum of its parts. GIS have emerged as very powerful technologies because they allow geographers to integrate their data and methods in ways that support traditional forms of geographical analysis, With GIS it is possible to map, model, query, and analyze large quantities of data all held together within a single database.
GIS is a special-purpose digital database in which a common spatial coordinate system is the primary means of reference.
Comprehensive GIS require a means of:
Data input, from maps, aerial photos, satellites, surveys, and other sources
Data storage, retrieval, and query
Data transformation, analysis, and modeling, including spatial statistics
Data reporting, such as maps, reports, and plans
GIS allows us to arrange information about a given region or city as a set of maps with each map displaying information about one characteristic of the region.