Posted on 08/07/2020 7:46:40 AM PDT by Red Badger
Good luck with your son and his experiments. Sounds like fun.
The approach makes all the sense in the world. When I was in the Navy I bought my own sextant (a bachelor with money to waste). Only used it a couple times, but one of those times I sighted a tight 3 line triangle of our position on a LSD sailing back to Hawaii from a West Pac cruise.
No big deal for a seasoned navigator who gets a good result all the time, but it was a thrill to me.
I threw the signalmen for a loop. It’s their job to stand behind and record the time of a reading and tell you the compass bearing and name of the next star to sight.
But I got a tip from the a library book that taught you how to identify the major navigation stars using a little mnemonic: “Captain, All De Rigging Seems Properly Polished”.
Starting with the highest star in the group in a loop downward they are Capella, Aldebaran, Rigel (belt of Orion), Sirius (the Dog) and Pollux (brighter than his twin, Castor).
Well the signalman thought it was a bit of magic for me to give them the sightings without being told which one is which.
The truth is very few stars are bright in the sky shortly after sunset. And those few are the ones we navigate with. So once you know the sequence, it’s child’s play to identify them.
But you’ve got to be quick. If you wait a few more minutes for more stars to appear, you’re too late because then the horizon is unclear, so can’t get an accurate measurement (60th of a degree) because you can’t precisely tell when the star bisect the horizon in the double scope sextant.
But getting back to the magnetic field GPS...
The principle is really the same. Except for measuring longitude at noontime, a sextant doesn’t do you much good without a Nautical Almanac, which is simply a data feed on the projected position of the planets and stars at a certain time of day of the year.
In a similar way, using a magnetic field locator is only as good as the research from satellites and maybe ground devices that read the contours of the earth magnetically - and project how they’ll change as the Earth circles the Sun.
The end user device reading is simple — on a plane, ship, car, or missile. The secret is the clever way the magnetic fields are measured.
Three cheers for the ingenuity of man! The part now is keeping it a secret from the Chicoms.
Very cool, Covenantor...
Thanks
;>)
*ping*
Possible Telluric electrical current in the Earth’s crust.
Interesting!
The Air Force belongs to American taxpayers.
What, no navigators on the B-2?
You are talking about TERCOM navigation which is terrain comparison navigation which uses an altimeter to measure the terrain contour or change in contour below the missile which is then compared to a grid of known elevation points or change contours and a position fix is obtained at a specific time epoch. MAGNAV works in nearly the identical way a high sensitivity 3 axis magnetometer measures field gradient, strength ,and orthogonal directions of the geomagnetic field. No two places on earth will have identical field vector, strength, or polarity. A high resolution base map of these magnetic parameters would allow the same types of least square or Kalman algorithms to correlate to a unique location at a fixed time epoch. There’s a version of this form of navigation using gravity and gravitometers that the military uses it’s accuracy is highly classified as are the sources of gravity map data over vast areas denied of ground level access and the types of 3 axis gravitometers sensitive enough to resolve unique gravametric solutions. 30 meters is about the theoretical accuracy level for magnetic data, gravity would be an order of magnitude better in “theory”
they’ve a got a replacement technology...only costs another 30 billion or so...
“they’ve a got a replacement technology...only costs another 30 billion or so...”
I guess we can otherwise spend the money on the Homeless, but I prefer that our military not blinded by China/Russia resulting in the US getting our asses kicked.
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