In 1953 an Institute working party was set up to investigate the accuracy of dead reckoning in air navigation and to attempt to produce error data covering a wide range of operational conditions. Dead reckoning errors fall into two categories, those due to wind finding and forecasting, and those due to instruments. Mr. Durst's paper surveys the whole problem, laying particular emphasis on the meteorological aspects, and represents the main progress in this subject to date.

The error of a dead reckoning position in the air will depend on the accuracy of the initial position from which the departure is made, the accuracy of the course steered (compass error), the accuracy of distance flown (airspeed-indicator or engine-revolution error), and the accuracy of the wind used (forecast error, found-wind error, &c). These quantities can be expressed mathematically, as is done in Appendix I, and it will be seen that if a pair of fixes is available it is possible to derive the dead reckoning error. The standard error that will arise when a large number of D.R. positions have been calculated on different occasions using a large number of aircraft and observers can be written symbolically; the expressions are fairly simple provided that the errors made in the different classes listed above (e.g. the errors in compass and distance run) are not closely correlated.