How does GPS work

I did a small research on GPS through the Internet recently.As i got my uni vacation,I used my free time to find some information about this technology.I was surprised when I found how this thing works.The credit goes to the US government.Although people are used to find faults about US always,at this point I am thankful to them.Because of them we are experiencing the advantages of this great technology.

People have a belief in them that a satellite is what gives all this information,but that is just a part of the real story.The real thing works like this.

It is not just a satellite which does this thing.we need 3 satellites in order to find a 2d location and more to find a 3d location,and in the space,we have got 24 satellites in order to determine the location of different GPS receivers all around the world,and US owns them all.

I was thinking about the difference between 3d and 2d location for a while.Then I came to a conclusion like this.Suppose if you are in the 20th floor of the world trade center.The 2d location finder could find the exact place you are(i.e you are in the world trade center),but not the floor(i.e in how much height you are),but the 3d location finder should give the details above mentioned plus the height you are from the sea level or a reference ground.

GPS receiver is all about measuring time.It sends signals to different satellites and compares the time difference of each signal to reflect back.According to the satellites' positions at that specific time,the GPS receiver determines the location of the user.remember the satellites are not in equilibrium.They orbit around the earth twice a day.If you are interested,find about how the distance measurement works in a GPS.It is just a simple theory of mathematics;the cosine rule.

Wondering about the beauty of Mathematics.