Tutorials and links

GPS tutorial basics

GPS Compendium
Even miniature GPS receivers feature position accuracy in the meter range. But do you know how these tiny devices achieve such stunning accuracy using signals from satellites more than 20,000 kilometers away?
u-blox' GPS Compendium is a tutorial designed to introduce you to the principles behind Global Navigation Satellite Systems.
GPS_Compendium(GPS-X-02007) 6.1 Mb

u-blox' GPS Dictionary
Acronyms, Abbreviations and Glossary related to GPS 
u-blox GPS Dictionary 247.6k

Origins of GPS
The original system study, the key innovations, and the forgotten heroes of the world’s first — and still greatest — global navigation satellite system. 
The Origins of GPS 4.4MB

GPS data resources and links

GPS Status and Outage Information
GPS status Information concerning maintenance outages, satellite launches and removals, and notices of changes to GPS operations are posted on this website run by the US Coast Guard. This information is generated by the Air Force 2nd Space Operations (2SOPs) as operators of the GPS system. 

Information and current status on WAAS (Wide Area Augmentation System) and EGNOS (European Geostationary Overlay Service). 

The National Marine Electronics Association (NMEA) is a U.S. standards committee that defines data message structure, contents, and protocols to allow the GPS receiver to communicate with other pieces of electronic equipment. NMEA 0183 is the standard data communication protocol used by GPS receivers. 

RTCM SC-104 (Radio Technical Commission for Maritime Services Special Committee 104) recommendations define the correction message format and various different correction message types. 

GPS Signal Specifications

GPS SPS Signal Specification specifying GPS SPS (Standard Positioning Service) signal characteristics and the minimum requirements for receiving and using the SPS ranging signal.

GPS SPS Signal Specification Annex This document consists of three Annex to the GPS SPS Signal Specification.

GPS User Equipment Introduction describing the basic principle of operation and algorithms and ideas of the GPS System.

GPS Interface Specification (IS GPS 200) describing Signal Structure and Payload as transmitted by the GPS satellites.