Concrete arrows of the sky: Relics of early Air Navigation
In the USA, enormous overgrown concrete arrows once served as navigation elements. These large symbols, visible from great heights, are a remnant of an old system that can be considered a precursor to today's GPS.
25 November 2024 13:19
These concrete arrows were part of a bold project from when aviation was just beginning to develop. The pioneering task of airplanes was to transport mail. However, as this task developed, a challenge arose: how can we navigate effectively to reach the destination precisely? In areas with diverse landscapes, distinctive points could be used as indicators. The problem arose on vast plains where pilots primarily had to rely on the sun. At night, when the sky was overcast, navigating by stars was also difficult.
Transcontinental Airway System – how was navigation formed?
The solution to these problems was the ingenious Transcontinental Airway System, which served as the postal infrastructure on a large scale.
Beginning in 1923, markers were constructed — large, several-metre-long concrete arrows covered with bright yellow paint, visible from a great distance, even from an altitude of 16 kilometres. At the top of each arrow, a concrete platform was installed with a 16-metre lattice navigation tower, which, like a lighthouse, was equipped with a 60-centimetre spotlight activated at night.
Additionally, each installation had coloured lights emitting Morse code signals with an identifier. In areas without power lines, small houses were built with power generators.
Within a year, arrows placed every several kilometres outlined a route connecting New York and San Francisco, covering nearly 4,330 kilometres and utilizing 284 markers.
The concrete navigation system proved to be effective. Previously, mail was transported by cars at night, but with the Transcontinental Airway System, flights became possible around the clock. The infrastructure included emergency, lit-at-night runways every several dozen kilometres.
Concrete arrows on the continent - what are they used for?
Thanks to the Transcontinental Airway System, delivering a letter across the USA took only two days. The system quickly expanded to 1,500 arrows outlining a network of 28,970 kilometres of airways.
Soon, however, modern technologies, such as radio navigation, began to replace this infrastructure. During World War II, some installations were dismantled to avoid aiding navigation for enemy air forces.
Many concrete arrows still survive today. To see them, just use Google Maps. Currently, 14 active markers still function in Montana.
