Several military and commercial platforms are currently installing GPS and inertial navigation sensors concurrently with the introduction of high-quality visual capabilities and digital mapping/imagery databases. This enables autonomous geo-registration of sensor imagery using GPS/inertial position and attitude data, and also permits data from digital mapping products to be overlaid automatically on the sensor imagery. This paper describes the system architecture for a Navigation/Electro-Optic Sensor Integration Technology (NEOSIT) software application. The design is highly modular and based on commercial off-the-shelf (COTS) tools to facilitate integration with sensors, navigation and digital data sources already installed on different host platforms.