[Milsurplus] AN/APN-1 Mission

[John Kidd]

Hi all,

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


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