The dramatic increase of Location Based Services and other location and navigation applications gives rise to a crucial need to improve positioning solutions. Currently, the American GPS is the only operational satellite based positioning system as the European Galileo system will be operational by 2010. Hence, this paper only deals with GPS receivers. The Time To First Fix (TTFF) and the sensitivity are the key drivers for their performance evaluation. The TTFF is the time needed for a GPS receiver to provide a first position. The sensitivity is the ability of a GPS receiver to acquire weak signals. For commercial solutions, an efficient receiver is a receiver with a reduced TTFF and high sensitivity. But generally, enhancing the sensitivity results in an increased TTFF and vice versa. In this paper, a use case will be defined which proposes an optimized solution to be applied in each type of GPS terrestrial environments, namely rural, urban and indoor environments.