GPS and GIS... whats it all about... can it work in Malaysia?? GIS Maps?? Part 1

OK we gotta start with the basics...

How do we calculate the XY position on the earth’s surface?? GPS (Global Positioning System) tech is now widely used to do this.

How did this come about?? GPS is a satellite based navigation system developed by the US Department of Defense. Yes, its usage was mainly in military and spying… focused mainly on military based applications. In the 1980s this changed … civilians can use it too. GPS is good because in works in any weather conditions… anywhere in the world… 24 hours a day.
To get into more technical details… GPS satellites circle the earth twice a day and transmits signal information to earth. There are about 24 satellites orbiting…

So the GPS receiver then receives this information from the satellite… and uses trangulation to calculate the user’s location. Actually what does the satellite transmit?? How is the location calculated??

It works like this… the satellites actually transmit time / clock signals to the earth... there is an internal clock in the GPS satellites. The GPS receiver then compares the time a signal was transmitted by a satellite with the time it was received. The time difference between the signal time and receiver time tells the distance between GPS satellite and receiver. This is for one signal. To actually get an exact location of a point on the ground you need more than one signal… from different satellites … this helps to calculate the measurement in a triangular position. Cool huh…

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.