[Milsurplus] AN/APN-1 Mission

[John Kidd]

I was reading an article about navigation over the years. One described the 
use of radio navigation to determine drift.

"Long over water flights relied on dead reckoning Dead reckoning required 
knowledge of drift. Sometimes drift could not be observed due to clouds 
below, or over water. Navigators used the known relationship between 
isobars, lines of equal barometric pressure, and wind. The wind direction is 
nearly parallel to isobars, and wind speed is greater where the isobars are 
closer together, that is, in areas where air pressure is changing rapidly. 
Navigators could measure changes in barometric pressure by comparing their 
pressure altimeters with a radar altimeter that gave true height above sea 
level. Therefore from the rate of change of pressure, they could obtain an 
accurate wind component."

Cheers,

John Kidd