Barbara M. Linde 
All About Road Maps and GPS [PDF ebook] 

What highways go from Maine to Florida? What’s the distance from Los Angeles to San Francisco? How do I get to my friend’s house? How does GPS work? As readers enjoy this volume, they will find answers to these questions and more. Readers learn to use the map key to identify different types of roads. They’ll plan routes for long and short trips, calculating distances with the scale of miles. After studying diagrams of the GPS, they will give a basic explanation of how it works.