http://www.ehow.com/about_5765705_functions-gps-tracking-system_.html
http://electronics.howstuffworks.com/gadgets/travel/gps4.htm
https://www.youtube.com/watch?v=0n0T992ccik
http://www.trimble.com/gps_tutorial/howgps-measuring.aspx
http://www.mio.com/technology-history-of-gps.htm
http://www.ehow.com/list_5912431_advantages-disadvantages-gps-systems.html
http://www.nasa.gov/sites/default/files/images/190844main_GPN-2002-000166_full.jpg
http://www.bisbos.com/images_spacecraft/sputnik_1_800.jpg
http://upload.wikimedia.org/wikipedia/commons/3/39/Transit-1A.jpg
http://www.astronautix.com/graphics/z/ztransit.jpg
http://timeandnavigation.si.edu/sites/default/files/multimedia-assets/520-77305a.jpg
http://media4.s-nbcnews.com/i/newscms/2014_29/569616/140707-flt-007-filer-1p_58d4c9649eb7418f07a6d9523c22414c.jpg
http://timeandnavigation.si.edu/sites/default/files/multimedia-assets/520-nasm-7b31753.jpg
http://im.rediff.com/news/2011/aug/03sli8.jpg
http://i.ytimg.com/vi/9VA4W1wDMAk/maxresdefault.jpg
http://cdn.sheknows.com/articles/gps-in-car.jpg
http://eduscol.education.fr/orbito/system/navstar/images/navstar1.jpg
http://upload.wikimedia.org/wikipedia/commons/e/e2/GPS-constellation-3D-NOAA.jpg
http://i.stack.imgur.com/FVsHS.gif
http://www.audiovideodirect.net/media/catalog/product/cache/1/image/1200x1200/9df78eab33525d08d6e5fb8d27136e95/g/a/garmin_010-00924-02_montana_650t_gps_receiver.jpg
http://news.nationalpost.com/2014/03/18/flight-mh370-went-missing-after-transponder-was-shut-off-why-do-planes-even-have-an-off-switch-for-crucial-device/
http://i3.mirror.co.uk/incoming/article3580124.ece/alternates/s2197/MH370-Main.jpg
https://www.youtube.com/watch?v=PLjld-edVj8