GPS technology has the potential to become of the most miraculous tools for saving lives. At the moment, most GPS devices work great only if they are out in clear settings. The GPS satellite orbiting the planet sends down low level radio transmissions to be picked up by your GPS handheld device. However, these transmissions often can t go through rocks, buildings or trees. If you are trying to find your way through the woods in deep winter, your GPS might be useless. So, here s a summary of a GPS comparison made by the United States Department of Agriculture Forest Service.

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p>Test Parameters

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p>These GPS comparison tests were made in the summer of 2000, about a generation of GPS devices ago. Most of these models or updated versions are available. Three test courses were used in three National Forests and training centers in Montana, California and Idaho. The goal was to work under very thick forests in the height of their foliage. There were about five volunteers in the GPS comparison study.

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p>Devices Compared

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p>The GPS comparison was between:

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p>Rockwell PLGR-96

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p>Trimble Pro XR

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p>Trimble GeoExplorer 3

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p>Magellan Map 410

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p>Garmin GPS III

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p>Summary

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p>The GPS comparison also included how accurate the GPS devices data was to where they actually were. They found it was very hard to get an accurate reading when directly under a tree. They still needed to try to get a clear patch of sky in order to get an accurate reading. Not only that, they needed to see a recognizable constellation, like the Big Dipper. One of the advantages of a forest is that stars are much more brilliant because artificial lighting isn t covering them up.

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p>In the end, the GPS comparison did not recommend the Rockwell and the Trimble Geo 3. The Rockwell is professional device of $10,000 and well out of the reach of any camper or mountain rescue unit. All of the other units of handheld GPS devices were recommended. But the costs of GPS devices have lowered considerably since the 2000 GPS comparison tests.

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p>They also recommended purchasing additional antennas that can be attached to most GPS units to amplify the reception of the GPS satellite radio signal. Some GPS units now come with antennas that can extend out like a transistor radio antenna. These antennas often fit cellular phones. The GPS comparison test showed that the latest technology and latest models were more cost efficient in finding out where you were in the forest.