The development of digital databases for airborne applications

Abstract

A joint project was born in the mid 60s between the US and UK cartographic agencies to develop a Digital Radar Land Mass Simulation (DRLMS). It was also recognised that such a database was needed to provide the core requirement for the developing concept of terrain referenced navigation, later to become the TERCOM system used in cruise missile guidance. Other possible applications emerged such as line of sight communications design, selection of mobile surface-to-air missile sites and passive terrain following systems etc. This led to a change of title for the project to the Digital Land Mass System (DLMS). The terrain database (DTED) provides elevation information in metres above Mean Sea Level (MSL) against a matrix structure based on the World Geodetic System (originally the 1972 version but now WGS 84). DFAD is the cultural database of DLMS and was developed to contain natural and man-made features in a vector format using a sequential structure. DTED and DFAD were initially developed primarily for radar simulation purposes. When it became obvious that systems were being designed using DLMS in manned aircraft, another database had to be added-DVOF. This is a list of all known man-made obstructions taller than 46 metres above ground level, although lower obstructions can also be entered. The database structure has a fixed file format based on WGS 84 and provides obstruction height as both AMSL (Above MSL) and AGL (Above Ground Level).