Servo - July 2010

quality is saved so that if the application cannot see any satellites, it stops updating the GPS location of the robot. If this is not done, you will start reading invalid values. latitude

long i tude

Building the Web Page

Once you know the location of your bot, it is time to map out the location in the Google Maps API. The Google Maps API lets you embed Google Maps in your own web page. With a latitude/longitude, the server is able to map the location of the device on a web page. If the device is located on a street that supports Google Street View, then this is also drawn on the web page. (See the figure for the web page example.)

The web page that is displayed to the user is separated into two different maps. On the left, a map is centered on the area that was last received by the local GPS location object. On the right, a panoramic picture of the nearest street location supported by Google Street View is displayed. If no nearby street is supported by Google Street View, the image is not rendered.

Initializing, drawing, and centering the map are completed with two lines of code calling the Google API.

 var map = new GMap2(document.getElement
 ById(“map_canvas”));
 map.setCenter(new GLatLng(<!
————————FUNCTIONCALL getLat —>,<!—
FUNCTIONCALL getLon —>), 16);

The FUNCTIONCALL comment in the HTML code is a utility function provided by NetBurner that allows HTML code to call C/C++ functions prior to rendering the web page. In this case, the functions getLat and getLon are called. These are functions that return the most recent

latitude and longitude in plain text.

Creating the panoramic view works in a nearly identical way. The difference is that instead of creating a GMap2 object, a GStreetviewPanorama object is created. Once created, you center the view on your location with a setLocationAndPOV API call.

Additional Capabilities

Many options exist to extend this application with a little work. Logging incoming data to your web server will allow you to create a path in Google Maps to track the entire journey of your robots. Directions could be sent to the robot via text messages, turning any phone into a navigational device. SV