The Pioneer SmartCradle for iPhones is compatible with all GPS enabled apps, including MotionX-GPS Drive and is the first of its kind to incorporate a built-in gyro sensor and accelerometer combined with an external antenna for improved GPS reception and location accuracy, even if GPS signals are limited by high rise buildings and tunnels.

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America is planning to improve its satellite-navigation system further: next year, it will start launching a second generation of GPS satellites, which will offer greater accuracy for civilian users and, for military purposes, greater protection against the signal being jammed by an enemy.

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For example, researchers in Arizona are using real-time kinematic global positioning systems, an ultra-precise version of GPS that can measure positions with sub-inch accuracy levels, to control weeds in cotton fields with steel cultivators.

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Not only does it use GPS co-ordinates for mobile telephony, but also refines its accuracy using cell masts to better locate a shop or restaurant in a large building.

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The researchers said that if GPs evaluated people who might have depression over two appointments instead of one their diagnostic accuracy rate would rise to 90%.

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The costs of producing GPS chips is dropping constantly and a new generation of satellites that will deliver improved accuracy are due to start reaching orbit by 2008 or so.

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By supplementing the GPS data with accelerometers and gyroscopes, researchers can use direction changes and speed to fill in the blanks, improving accuracy from a crude-at-best 49 feet to between 3 and 7 feet.

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