A GPS enabled Emergency Messaging System (GEMS) includes: Emergency Response Centers (ERC's) for defining emergency broadcast messages directed to specified geographic areas; a GPS Control Segment (CS) facility that receives messages generated by the ERC's and coordinates uplink and downlink communications with orbiting GPS satellites; a GPS Space Segment (SS) that includes the multiple orbiting GPS satellites and that receives emergency messages from the CS facility and broadcasts transmissions containing both GPS navigational information and an emergency broadcast message; and GEMS-enabled user equipment that is capable of receiving and processing broadcast emergency messages. The system permits emergency messaging data to be superimposed on the existing GPS signal structure and delivered to users with GPS receivers capable of receiving the superimposed messaging data.