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aSDR1

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5	5	=== Introduction ===
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7		The use of GPS services growing just as fast as the development and accessibility of mobile devices. A GPS devices, which used to be a significant investment, is now included in every smartphone that emerges on the market. These services have assisted many as they navigate themselves from place to place outdoors.
	7	The use of GPS services is growing just as fast as the development and accessibility of mobile devices. A GPS devices, which used to be a significant investment, is now included in every smartphone that emerges on the market. These services have assisted many as they navigate themselves from place to place outdoors.
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9	9	Although GPS is well-defined outdoors, localization indoors is still an active research problem. GPS signals indoors tend to be weaker; even if they are usuable, the accuracy associated with GPS signals is not up to par. Large errors (on the order of meters) associate with GPS generally do not affect the user's ability to navigate to buildings, parks, landmarks, etc. Errors on the order of meters indoors, however, could mean that somebody is in a different room or different building altogether. A fine-grained service, down to the centimeter, is needed to localize indoors.