A training film introducing the air map and how it is used as an essential guide for navigation. The basic concepts are explained for low medium and high flight. The ability to correlate features on the ground with their representation on air maps is paramount, as is the concept of lapsed time during a flight. The film follows a predetermined flight path at a height of 3,000 feet, which is repeated at low level.
Map reading is still the most accurate method of locating and fixing of position, and is regarded by pilots and navigators as a vital essential skill should other means of navigation employing instrumentation fail. The main principle of air map reading is the correlation of symbols on the map with features on the ground. To avoid complication only features which are essential are marked on an air map, hence some features seen on the ground will not be seen on the map. Cut to close up of air map showing a town. On the contrary every feature on the map will be located on the ground with very few exceptions. To plan a route, a line is drawn on the map representing the flight line, and observing the convention map to ground viewing, recognisable features are noted along the flight line. Major topographic (rivers, lakes, woods hills) and cultural (railways, roads, towns) are useful features to look for but their identification is dependent upon your height and climatic conditions.
Film cuts to aerial view at 10,000 feet. Adequate time to look but many useful features are not seen at this height. Cut to aerial view at 5,000 feet and now many road and field boundaries can be identified. Cut to a very restricted view flying at tree height when only features such as distant hills are identified. Photographic views of the navigational value of a variety man-made and natural features, seen at a range of heights now follows, whilst the commentator lists their relative value as navigational aids. The representation of these features on a map is discussed.
"Exercise at 3,000 ft": A cross country circular flight (flying to starting point) is demonstrated. The flight path is drawn on the map, potential navigational features noted, and the aircraft takes of from RAF Hullavington and climbs to 3,000 ft. remaining at this height for the duration of the flight. The map is orientated until the drawn line is parallel with the aircraft's flight track, as the first feature, Stroud, comes into view. The commentator indicates the associated features that confirm the fix. The flight continues, Ledbury, Ludlow, Shrewsbury and Ellesmere, are passed in similar fashion. The aircraft turns onto the second leg at Birkenhead, and the third leg at Southport, the map reoriented at each turning point. The exercise continues, flying over the Pennines, down to Lincolnshire (passing RAF Cranwell) and back to Hullavington. Throughout the exercise the commentator has made good use of the very varied terrain to indicate how a 'target' (the topographic fix) may be confirmed by looking at auxiliary features.
"Exercise at low level": Map reading at low level is more difficult than reading at medium to high levels. With modern aircraft speeds are such that at low level features are only in view for a few seconds. The features used so far cannot be seen at low level, and it is thus necessary to depend upon a careful pre-flight study of the route integrated with lapsed time as the aircraft proceeds along the flight path. Anticipation of what lies ahead and when, is the guiding principle. The flight will be made following the first two legs of the 300 foot exercise. Study of the map will reveal which features may be seen at low level (river valleys, prominent hills etc) and committed to memory. The question of lapsed time is now considered. The ground speed or air speed is calculated to be 180 knots or three nautical miles per minute. The flight path is drawn on the map, as before, and marked every fifteen nautical miles or five minutes flying along the marked track.
Film cuts to view from cockpit as the aircraft departs Hullavington flying low up the Stroud valley. Major river and road features are noted, and 23 minutes into the flight the annotated map indicates the aircraft will be over Shrewsbury in 2 minutes time. The fix is is duly confirmed as the aircraft passes over the distinctive river and railway pattern. The flight proceeds in this manner as major features appear on schedule with the time marks on the map. The flight ends at Southport, on schedule after 40 minutes flying time.
The art of air map reading is learnt from experience – gained by practice. The film is designed to show the basic principles of the art, intelligent use of the map, correlating features and the importance of time.