ecblackiii Loc: Maryland

A fascinating story, told by the people who made the miracle happen!

Merlin1300 Loc: New England, But Now & Forever SoTX

Probably a little known fact that the GPS algorithm must use Einstein's theory of relativity to compensate for the relative speed of the radio transmissions from each satellite. As the dielectric constant of the ionosphere changes - so changes the speed of the electromagnetic waves through it.

Schoee Loc: Europe

I hope you did not believe his theory on the accuracy being 3/8ths of an inch.

DirtFarmer Loc: Escaped from the NYC area, back to MA

Such accuracy can be achieved using ground-based local signals.

Schoee Loc: Europe

That would not be the Omega system then you mean? I don’t think even differential GPS has that accuracy. Differential GPS best can get about half to one and a half inches.

DirtFarmer Loc: Escaped from the NYC area, back to MA

Depends on how local we're talking about. Location systems on a farm want to be pretty accurate. If you're cultivating a crop you want centimeter accuracy to avoid wiping out the crop.

A long time ago I thought about how I could define a simple system to locate my cultivator. Then I could use a robot in the field to keep it weeded. Thought about sonar, easy to produce and detect signals, timing of signals is fairly coarse so fine intervals could be detected, but then I realized that sound signals are going to be affected by wind, so a breeze would create an offset that you would have to correct for, and wind fields are not always uniform across large areas so you need additional wind sensors to do the correction and it got out of hand.

Robot weeders do exist now, but they're out of a small farm budget. So the kid with a hoe is cheaper (although they need calibration).

Robertski Loc: So California

I've been thinking how useful GPS is and just bought a USB GPS Dongle so my desktop computer can use programs (weather) that can use Lat & Long. In 1978 I crewed a sailboat to Tahiti that the owner had installed the Omega satellite system on. The Omega could skip lanes by about 20 miles each time, so by the time we got close to French Polynesia, the Omega was 60 miles off course. I had time to learn how to use a sextant, so I trusted it instead. 60 miles is enough to miss an island entirely. We avoided low atolls that were only as tall as their palm trees, due to all the stories of sunken ships on the reefs. I now see YouTube videos of how wonderful those low atolls (Tuamotus) would have been for diving and lagoons. Now days, GPS would allow a boat to find the inlets more safely. I do have a yellow 1971 VW bug in the garage, so maybe I'll install the tape deck to get around if I ever get it running.

Merlin1300 Loc: New England, But Now & Forever SoTX

Parkinson knew Omega was Crap - though the Navy took years to admit it.
Just get an iFoan or Android Phone - or maybe a stand-alone Garmin etc.
Their current GPS Nav Solutions will get you within feet of where you want your sailboat or Anyboat to be.