The present invention is related to location positioning systems, and more particularly, to a method and apparatus for making accuracy improvements to a GPS receiver's navigation calculations. According to a first aspect, the invention provides an extreme sensitivity GNSS tracking architecture. According to other aspects, the architecture includes multiple loops per channel, with the loops implemented with hardware and/or software. According to still further aspects, the architecture includes a multi-level lock detection algorithm designed to provide a trade-off between sensitivity and speed that is not possible with existing tracking architectures.