An example of an early airways strip map guide from 1928
Aeronautical Maps
Until the 1920's most pilots relied on the Aeronautical Bulletins for accurate airfield data, but they had to rely on railroad and state road maps for navigation as there were few if any "official" aerial maps being produced. While road maps contained detailed information useful to travelers on America's roads, to a pilot flying at 2,500-5,000 feet the boundary lines, and other such information indicated on such maps was of little use. And in winter frozen and snow-covered rivers which were marked on maps were difficult to locate. At an altitude of 5,000 feet, with favorable visibility a pilot's horizon extends over an area in excess of 30,000 square miles! Thus his eye is naturally attracted to those features which stand out in such a vast vista. Railroads, cities & towns, lakes and other natural landmarks were of primary interest to such men, and the development of specialized maps for aerial use became an important concern as aviation grew.
The Army Air Corps and aviation branch of the U.S. Navy had produced a few maps in the early 1920's, but it was not until around 1926-27 that the Department of Commerce, under the Air Commerce Act, was tasked with the responsibility of charting civil airways and publishing aerial maps. The actual survey work was carried out by the Coast and Geodetic Survey a bureau under the Commerce Department. Until the 1930's three separate agencies produced maps. The Air Corps and the U.S. Naval Hydrographic Office both produced maps, as well as the Department of Commerce. While the Air Corps and Commerce Department published in 10-1/2 inch widths, the Naval maps were 15 inches wide. Yet both sizes provided the pilot with an 80 mile representation along his route providing a 40 mile deviation to the right and left of the airway being followed.
The early federal program undertook to create and publish airway "strip maps". These maps were designed to provide pilots a map covering 330 miles of flight information. The scale of these maps was set at 1/500,000 (approximately 8 miles to 1 inch). They were published on heavy stock paper which would hold up to the rigors of repeated in-flight use, and were printed in three colors (red for airfields and other navigation aids, as well as prominent hazards; black & red arrows indicated local magnetic deviations; useful topograhic features such as mountains, streams and bodies of water were printed in contrasting colors). Other features added on later maps included: balloon and airship facilities, lighted beacons, radio beacons, radio stations, and radio compass stations. The maps measured 24-48 inches in length by 11 inches wide, and cover approximately an area of 80 miles in width and 200-400 miles in length. This format remained in use until after World War II, when advances in radio navigation and increased speeds and ranges of aircraft required more elaborate mapping techniques.
A number of non-government agencies undertook publishing of other aerial maps. The Rand McNally company of New York published the "Standard Aviation Map" in the 1930's which was used at flight training schools throughout the country.
The following examples are illustrative of the maps which were available to aviators of the late 1920 and 1930's.
An example of an early airways strip map guide from 1928
Airway Map no. 129 (Greensboro, North Carolina to Richmond, Virginia)
(courtesy of the Virginia Avaition Museum)
(click for larger image)
An example of a later version of the strip map from 1933 (showing the radio
beacons)
A 1933 "key sheet" indexing the 87 airway maps covering the U.S.
As can be seen from the above examples, modern sectional charts have their origins in the Golden Age. It should also be mentioned here that an airline pilot, Elrey Jeppesen, kept a meticulous set of notes on his routes which he later incoporated into a series of published pamphlets he then made available to fellow aviators. It was these pamphlets which marked the beginning of one of the largest producers of aeronautical data today -- Jeppesen Company.
To learn more about Jeppesen click on the book
Today it is very difficult to locate copies of early aeronautical maps. One can only surmise that as their usefulness diminished they were discarded, much to the frustration of modern researchers. Yet, every once in a while an example does show up at auctions. I have occassionaly seen examples appear in classified sections of historical aviation journals, and even on the internet auctions pages such as Ebay.Com. If you are fortunate enough to purchase one please let me know.
!!UPDATE!!
(click)I recently discovered a useful guide for reading strip maps.
2003 Wings Publishing