In May 1993, in support of Eurocontrol's WGS 84 Implementation Programme, a project was undertaken to assess the accuracy of navigation aid coordinates. The exercise involved flying a route over a number of European countries, in an aircraft which was equipped for multi-DME ‘data puddle’ position updating, and which also carried Global Positioning System (GPS) receivers. This test flight, carried out under contract to Eurocontrol, involved two parties, namely the Defence Research Agency (DRA) Bedford, who provided the airborne trials facility and DME data, and the Institute of Engineering Surveying and Space Geodesy (IESSG) at the University of Nottingham, who provided an analysis of the DME coordinate accuracy.

The aim of this test flight was to assess whether it is possible to determine independently the (WGS 84) coordinates of DME ground stations from the air, by using the same DME range measurements which are used to update aircraft position information in-flight. The procedure used to determine DME coordinates involves reversing the position updating principle. Instead of taking the DME ground station coordinates as known points and using the DME range measurements to determine the aircraft's position, the aircraft's position is independently determined (from DGPS) and the range measurements are used to estimate the coordinates of the DME ground stations.