. It is primarily used for military-grade receivers to output navigation, timing, and satellite status data. ASSIST-QuickSearch Basic Search (.mil) Overview and Purpose Standardization
In the early 1990s, GPS was moving from a strictly military tool to a commercial reality. However, hardware manufacturers were speaking different languages. You couldn't plug a Garmin receiver into a Rockwell-Collins flight deck without a custom interface card. icd-gps-153 protocol