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Chapter 8: GPS and a Real- T ime Situational Displa y           227


                             the red LED will be steady instead of blinking. The receiver’s hold sensitivity is much better
                             than the acquisition sensitivity, so the quadcopter can be put back to a horizontal position
                             while still locked onto the GPS signals.


                        Moving Map System


                             Note:  The original intent of this section was to demonstrate how to display the quadcopter’s
                                position in real time by using the Google Earth application. Unfortunately, I was never able to
                                stream the raw GPS data successfully from the XBee transmitter to the ground-station XBee
                                receiver, and then into a laptop running Google Earth. However, I do show you how to manually
                                enter the coordinates as they are displayed on the LCD screen so that you can have a near real-
                                time location service.
                                I  selected  the  Google  Earth  application  for  the  moving  map  display  because it
                             incorporates a very convenient interface that accepts serial GPS coordinates and can display
                             them on a computer screen in real time. This project was divided into several phases so that
                             I could  experiment  with  the various  technologies  involved  with the moving map and
                             determine how to best implement each phase. The first phase was simply to use an existing
                             hand-held GPS device plugged into a laptop running the Google Earth application.

                             Monitoring the Quadcopter Position
                             with the Google Earth Application
                             Figure 8.31 shows the Google Earth opening screen. I ran the application on a Win7, 11.3-in,
                             and 32-bit Toshiba laptop. You next have to click on the Tools menu bar selection to access
                             the GPS import function. Figure 8.32 shows the real-time GPS menu selection.






























                             Figure 8.31  Google Earth opening screen.
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