A Loran Navigation Fix

Using a restored WW2 APN-4 Loran navigation aid, this demonstration will explain how a simple fix is obtained using a Loran chart. Note that a minimum of two such fixes would have been needed to arrive at an actual location. Consider Loran as being a wartime equivalent of a modern day GPS receiver.

[@radoslawbiernacki]

Sir, I'm grateful that you shared this knowledge!

[@lishaton]

Thanks for the positive comment!

[@tomschmidt381]

I learned about the LORAN system during avionics training during the 1960s. I was a pretty clever system. It has been shutdown worldwide in favor of GPS. However my understanding is there is renewed interested in reviving it as a backup to GPS.

[@jodeldk]

We used loran c for surveying around the UK In the late 1970,s

[@lishaton]

There are currently several countries experimenting with what's called eLoran for use as a GPS backup. Do a google search if you want to know more! Obviously a lot more advanced than even Loran C by using modern technology.

[@itsonlyme9938]

Loran used to be on 1950khz and has been phased out about 20 years ago in the UK

[@lishaton]

Such a pity as it was a useful alternative to GPS. Mind you, have you read up on ELORAN? Have a look if you haven't! We had a small Decca navigator on our boat until that too was closed down. Once again a bit of a shame as it made a good backup and worked very well. One of the last times we used it was on an English Channel crossing to France, where we compared it directly to a hand-held GPS.

[@reubensandwich9249]

Amazing.

[@lishaton]

Thanks for the comment! :-)

[@ajlnfo6358]

Ah the old APN-4. The Navy was still training NFOs on the APN-4 in the mid ‘60s. My patrol squadron had a mix of A/C equipped with the -4 and others with the much better APN-70. Watching your nicely done video I can see why I had no love for the -4. BTW we had a -4 slide-rule-like device to assist in somehow determining the line of position. Years back I had one...but no more. I stumbled on this site looking for info on the -70. Any chance you have an ‘operable’ APN-70?
v/r AJL SP-5B NFO

[@lishaton]

Interesting! 'Fraid I'd never heard of an APN-70 until you mentioned it in your comment. Just did an Internet search to find out what exactly it was, but can findout minimal information along with a couple of indifferent pix. We do however have an APN-9 which will eventually be restored. Such a loooong job. There was so little left of our APN-4, that the chassis was stripped to nothing and we rebuilt it piece by piece... At least it works now :-) Thanks for theinformation!

[@uploadJ]

Interesting ... and I'll bet it took some skill when the weather involved lightning storms producing static 'noise' too that caused the observed waveforms to be obscured momentarily ...

[@lishaton]

Indeed it was. It takes long enough doing the demo' without any of that interference !

[@firmaneffendi2801]

So I had several question. I had read about LORAN Navigation in elementary school, yet still don't understand how the systems work until my 20s lol. To use the LORAN, we need to count the phase difference to get the first fix by calcuating our distances to the first station, while being backup by dead reckoning, is that true? The fix get more accurate by doing Trigonometri and symple phytagoras math out of several other stations is that true? Does this (video) method only apply for ships or air crew navigator did the same steps in the 70s? If not, what equipment did they use back then? Thanks before

[@lishaton]

Hi! Loran used TIME differences (like GEE) as opposed to PHASE differences between the signals. The Decca system used phase relationships.
Indeed one did need to start with a rough idea where one actually was, (by dead reckoning) in order to chose the transmitters from the chart that would be best used for the fixes. The more transmitters that were used for the fix, the more accurate the final position will be. You will of course need to use use at least two.The video shows the obtaining of just the one. As far as I am aware, the same techniques shown here were used both in the air and on board ships.
I am unfamiliar with the equipment used in the '70s, but can say that by the last decade or so of Loran operation, the entire procedure was taken over by a box containing a microprocessor that gave the Latitude and Longitude directly onto an electronic display. (Not sure if GEE ever did? I don't think so.)
Decca also ended it's days as a small 'box' which read out lattude and longitude onto an LCD display from a microprocessor.
However much quicker this was than by using the earlier methods, an example of the 'modern' Decca we used ourselves for several years in the early 1990s still needed to be 'told' a rough position where to start before it would provide a correct and accurate fix. I hope this helps!

[@firmaneffendi2801]

@@lishaton thank you very much! Never learn so much about them until recently. Glad to learn about other system such as Decca and Gee too, because I born in pure digital era, in which GPS are the current stuff, never know how LORAN and otger stuff work. Thank you for the information, very helpfull!