There are 24 GPS satellites orbiting at 20,200km in a 12 hour orbit which pin points our location and altitude anywhere on earth, any time! GPS can also be used for determining our speed and heading. It is widely used for tracking and many other very useful applications. For civilian use their accuracy is in the order of 20 meters but it varies depending on how many line of sights between the GPS receiver and satellites is uninterrupted at the same time. This depends on the location of the GPS receiver, date, and time. For determining ones location at least 3 and to get the altitude information 4 satellites have to be in line of site with the receiver. GPS satellites broadcast at 1.575 GHz which is attenuated in the ionosphere and troposphere. The radio signals sent by the GPS satellites attenuate during their journey of 20,200 km to the GPS receiver. There are issues like reflections, multi-path reception, cycle error, loss of reception which also brings inaccuracies to the picture. Accuracy is also determined by the GPS receiver sensitivity, processing hardware and the algorithms used in processing the information sent from the GPS satellites. Its accuracy mainly depends on how many and how well the GPS receiver can processes the received signals coming from different GPS satellites at any time. There is always a need of knowing the accuracy of a GPS hardware at any chosen time and place or compare one hardware to another objectively. Once positional accuracy is determined then one can calculate the error bounds in speed and bearing. This can be “only” done by marking the GPS coordinates on the map and comparing it with the predicted coordinates. The accuracy numbers produced by the GPS hardware are basically error bounds of the location for a given percentage of readings. So these numbers are not “real”, because in reality GPS does not know its “real” position on the earth. But these numbers give a good idea about the error bounds. Using the map support functions of the GPS Tester one can mark its present location on the map. The second step is selecting the duration of the test at a stationary location. After a period of several minutes of warming up the GPS receivers will calculate its position and will check the way of increasing its accuracy. After initialization typically GPS will start giving coordinate information every second. The GPS data given by the GPS receiver module will be compared to the “actual” position which was marked from the map. It displays the calculated position and altitude and gives the accuracy based on the marked position and calculated position over the specified period of time. So basically the user becomes the tracker of the GPS satellites! It is fun and very useful for many applications like predicting the bounds of speed and heading errors based on location errors!
Satellite Viewer with Magnetic Compass! – This is a very easy to use polar diagram which has concentric circles representing the elevation angle of the GPS satellites and another perpendicular axes showing the North-South and East-West direction.
Colorful Dynamic Signal Strength Bar See the received signal strengths of each GPS satellite in a colorful display real time like in music sets.
Dynamic Colorful Display of GPS Satellites in Use See all the satellites in use or not used for GPS purposes.
See the GPS satellites as they orbit around the Earth in real time
Advanced Mapping Functions - Using Satellite and Street Map modes find your location and mark it as “reference” point. Distance between gps location updates. Zoom and Pan functions which moves you around the world with ease.
Scatter Plot of the Position and Altitude See and compare the “real” errors associated with the GPS location and altitude for a given duration of time.
Email the log of GPS coordinates and the actual coordinates. This feature is for data analysis of the error and for perfecting the algorithms.
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