Boat diving before GPS?

[Armymutt25A]

I know we've had civilian GPS for about 20 years now, but what did charters use before then to find wrecks out of site of land? Did there used to be some sort of radio beacon system set up for navigation? I'm kind of curious because I never saw a back up system on the boats I've been on. I suppose if the nav system failed, the trip would be over and the captain would use a compass to get within sight of shore.

[Brian Sharpe]

Prior to GPS LORAN (LOng RAnge Navigation) was (and still is) used, as you correctly observed it is based on multiple radio beacons and IIRC was developed for military use during WWII.

[dkktsunami]

I know we've had civilian GPS for about 20 years now, but what did charters use before then to find wrecks out of site of land? Did there used to be some sort of radio beacon system set up for navigation? I'm kind of curious because I never saw a back up system on the boats I've been on. I suppose if the nav system failed, the trip would be over and the captain would use a compass to get within sight of shore.

Long Range Aid to Navigation (LORAN) and prior to that, skill.

[DennisW]

LORAN is the backup to GPS, should the system fail. Doesn't do many of us pilots a lot of good since the manufacturers don't include a LORAN receiver in the GPS box, but many ships have both systems. Local dive operators along the coasts sometimes still use a method of lining up three or more coastal landmarks to pinpoint a dive site. It works fairly well, but things change too much for the landmarks to be completely reliable.

Oh yes, sextant and chart method is the most reliable of all.

[Hickdive]

Decca or Loran were earlier electronic systems but, if you were in sight of the shore and there were plenty of features on the shore, then most people used 'transits' (aka fisherman's marks and various other names).

Pick two objects on shore that line up when you're on the dive site and make a note of them. Pick another two objects that also line up, ideally as close to perpendicular to the line formed by the first two, and make a note of them too.

To return to the same spot simply line up the first two objects and drive the boat along that course until the other two objects line up as well.

Doesn't work if you can't see the shore or if there aren't any features to line up with.

Lots of wrecks were very difficult to dive before the advent of electronic navigation, simply because what is precise enough position fixing for navigating a ship isn't really precise enough for trying to locate an underwater object that might be only a few hundred feet long, at best.

[rstofer]

And then there were Radio Direction Finders where a rotating antenna was used to find the relative bearing to a broadcast radio station. Get a couple of relative bearings and you have a 'fix'. More bearings are better.

Better yet, there used to be a radio transmitter at Avalon (Catalina) which made navigation from San Diego quite simple. Circa 1963...

Richard

[HowardE]

Some people used "dead reckoning" to locate sites. Lining up with landmarks on shore to find offshore locations, combined depth sounders on boats

[Nemrod]

1. LORAN

2. We used maps, we took headings, we steered a course, we calculated time and speed and we used a bottom machine to then locate the spot once in the area.

3. Ranges, line up buildings on the beach, often used with (4) below.

4. Triangulate using a sighting compass to fixed objects visible on land. When the area is triangulated toss a buoy over, circle the buoy using the bottom machine to locate the spot.

5. Secret knowledge acquired by time on the water, learning the signs, having a sixth sense. The Panhandle of Florida, for example, it is relatively easy to know when you are over the wreck even before turning on your bottom machine, you might see birds on the water and fish circling, bait fish up on top.

It is kind of funny, people today are always amazed at how clever or capable humans were even a few years ago, yes, we could locate dive sites without GPS, airplanes crossed oceans without GPS, cowboys actually could shoot and hit a target with their six guns and even the Egyptians were able to build the pyramids, all without help from GPS or aliens.

N

[vladimir]

My dad left me his sextant and stop-watch.

[captain]

I still have my book that I recorded ranges in by simple drawings and notations and LORAN td's before GPS. LORAN was quite accurate when used to return to a site, equal to or better than GPS, but not as accurate as GPS when trying to find a site for the first time.