The iPhone 3GS has a built-in magnetometer - or compass. To use the compass open the Compass application. The compass works whichever orientation the iPhone is held - so you don't need to hold it flat and horizontal like a normal compass.

Obviously the compass shows you the direction of North - the figure at the top of the screen is the direction the top of the phone is facing - eg 220° SW.

The digital compass can be distracted by electromagnetic interference - to reset it move the iPhone 3GS around in a 'figure 8' pattern.

The Compass application also shows you the geographic co-ordinates of your current location in longitude and latitude - for instance 51°31'12"N, 0°8'17"E. Just look in the bar at the bottom of the screen for your current geographic location.

Click on the i button on the bottom right of your screen to switch the compass between True North and Magnetic North.

Click on the crosshair icon at the bottom left of the screen to go to your current loction on the Google Maps application.

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