GPS

GPS - Global Positioning System

GPS stands for Global Positioning System, built by the US Department of Defense in order to get a highly precise form of worldwide positioning.  It is formed by a constellation of 24 satellites and with their ground stations.  These satellites are used as reference points to calculate positions which are accurate to a matter of about 20-25 meters radius.  However, with a Differential GPS (DGPS) the accuracy improves within 3 meters radius. 

The basis of GPS is to be able to obtain "triangulation" from the satellites. Measuring the distance from one satellite narrows our location down to a particular sphere. The signal from a second satellite will also give a sphere, and the intersection of these 2 spheres gives us a circle which will effectively be the radius of our location.

The name of the GPS chip we are using is the Motorola M12. It operates on 3V and uses Motorola binary communication.  Below is the picture of the GPS chip and the antenna.

The objective of the project was to navigate the robot to a destination coordinate using GPS. Therefore the robot needs a heading to turn towards the destination point. As the robot moves, we stored seven coordinates along the way. These seven points are then used to calculate a best fit line using the method of least squares. From this we got a heading by which when the robot turned, it would face the destination coordinate. The figure below shows the least squares solutions for some random points which could represent a path.