Skip to main content

What is GPS?

            Having seen what GIS is, we will now have a look at what GPS or the Global Positioning System is! Wikipedia's following GPS definition says it all. "The Global Positioning System (GPS) is a space-based global navigation satellite system (GNSS) that provides reliable location and time information in all weather and at all times and anywhere on or near the Earth when and where there is an unobstructed line of sight to four or more GPS satellites."

           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. The 24 satellites 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.



            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.



             Today's GPS receivers are extremely accurate. Today GPS receivers are embedded in a large number of phones. Day-by-day, knowingly or un-knowingly the common man is getting more and more exposure to GIS and GPS technology based systems. Cheers to Geo!...
Labels:

Comments

  1. Hrishikesh PNovember 27, 2010 at 6:16 PM

    have you heard about USGS? Its one and only service provider for all GPS systems. Not even google provides its own map service, google too uses USGS. For more info visit usgs.gov

    ReplyDelete
  2. Shreerang PatwardhanNovember 27, 2010 at 6:20 PM

    Ya...It's the US Geological Survey...Isn't it?...Yes I know about it!

    ReplyDelete

Post a Comment

Please leave your comments here...

Recommended for You

Where does Google get it's live traffic data from?

Referring to a post that I wrote earlier, Google’s - Live traffic Layer , ever wondered how Google collected this data? I was wondering the other day, how Google received live data to display it on their maps as a layer! I looked up the web and found something very interesting and am sharing the same with you all. As we all know, the traffic layer is available most accurately in several states in USA. Most major metro areas in the US have sensors embedded in their highways. These sensors track real time traffic data. Easy to miss at high speeds (hopefully anyway, traffic permitting), more commonly noticed may be the similar sensors that often exist at many busy intersections that help the traffic lights most efficiently let the most amount of people through. The information from these tracking sensors is reported back to the Department of Transportation (DOT). The DOT uses this data to update some of the digital signs that report traffic conditions in many metro areas. They als...
17 comments
Read more

Playing with the markers and info window bubbles...

    In the last few posts, we have seen some marker examples and some information window examples. Now, lets do something interesting combining these two things. Just writing that "This is an info window" in the information bubble is not very interesting! And I know this...Have gone through the same phase!     So, today we will do something interesting! We will display the latitude- longitude co-ordinates of the point that the user clicks on the map! Doing this is not at all complex! Copy paste the following code and you will see for yourself a map coming to life!     The output of the above code looks as seen in the result section above! If you have any queries regarding the above code please comment on the blog post or feel free to contact me at my mail ID .
3 comments
Read more

Form info window

         Today we will look at a Google Maps API v3 example to add a form in the information bubble! This is usually required when we wish to accept some data/information from the user! This data can be saved to a server in the form of an XML file or a database! The information can then be retrieved back at a later stage, when necessary!          In this example we will only look at form in the information bubble! The connectivity part with the server will be discussed in another post! So, today's code snippet is as seen below! <html> <head> <title> Google Maps API v3 - Adding marker and info window on Click and creating a form in the infowindow with the lat-lng information in it. </title> <script type="text/javascript" src="http://maps.google.com/maps/api/js?sensor=false"></script> <script type="text/javascript"> var map;    //When using ev...
5 comments
Read more

Retriving co-ordinates...

         We have seen 2 Google Maps API v3 examples wherein we have retrieved the latitude-longitude co-ordinates of the point of click on the map. In the first example we have displayed the co-ordinates in the information window and in the second , we have displayed the co-ordinates in a form in the information window.         Today we will create a code to retrieve the latitude longitude co-ordinates in a text box while simultaneously a marker appears on the map as well. So, here goes the code. <html> <head> <title> Google Maps API v3 - Adding marker on Click and retrieving the co-ordinates in a text box </title> <script type="text/javascript" src="http://maps.google.com/maps/api/js?sensor=false"></script> <script type="text/javascript"> var map;    //When using event as a parameter to a function declare map, strictly as a global variable fun...
5 comments
Read more

Two maps on the same page - Side-by-side

    How good I am feeling to post a code example after such a long time! It's been all "news" over the past so many posts! Well now that I am finally doing a code example, I am posting a very highly requested code sample. Placing two Google Maps on the same page (Now that's simple you would say!), but side by side. Now this is the thing that most people struggle with. Well, implementing the second part is also very simple, as you will see in today's code.     Let's see the code. Here it is!     The output of the above code will be as seen in the result section above.     As most of you will realize, there are two maps, one centered at "Pune" and other at "Noida". Why I chose these two locations? Well, just like that!...The main issue of concern is how the maps appeared side-by-side and not one below the other as would be normal behavior of two "div" elements used in the same page. Now here is the trick! Check out the...
10 comments
Read more