[AT] Satellite Tracking was Warning and apology.

[charlie hill]

Gil,  I'm not near as up to date on it as I'd like to be.

As for precision it goes back to before today's world.
The guys that do things like setting up big steam turbines have to set 
anchor bolts, etc. to within a few thousanths of an inch.   I mentioned a PK 
nail earlier.  That is a little tack with a dimple in the head.  You drive 
it into a wooden stake or the highway so that (in the old days at least) you 
could hold a  plumb bob with the point hovering just above the dimple in the 
PK nail.  The line on the plumb bob has a sight on it for a the instrument 
man to sight in the transit on.  He already had the  transit  set up 
directly over the PK with the same precision using a plumb bob.  The transit 
we used was refered to as a "20 sec gun".  Meaning it would accurately 
measure an angle down to 20 seconds (60 sec in a min. and 60 min in a deg) 
Therefore 20 sec was 1/180th of a degree.

We also used that dimple as the point to hold the end of the tape to when 
"chaining".  We had to hook a spring scale like a fish scale to the end of 
the "chain" ( a steel tape) and pull the spring to a pre-determined tension. 
Then we had to correct the length of the chain for temperature variations. 
The instrument man would give us line by turning the correct angle and then 
we'd chain the necessary distance in order to go precisely to a point. (say 
357.65')  It's facinating work.  I wish I had stayed with it.  You'd be 
surprised what a bunch of dumb, redneck construction workers can do when 
they aren't at home working their tractors.  grins

As for LORAN, GPS pretty much put it out of business.  I'm not even sure 
they use it for differential to correct GPS any more do they Cecil?  In fact 
are the transmitters still up?   All I know is when GPS came out I put my 
LORAN away and haven't missed the dang thing.  If you think LORAN C is 
tricky you should have tried the first version LORAN A.  Just take the GPS 
and go with it.  Forget LORAN.

Charlie


----- Original Message ----- 
From: "Gilbert Schwartz" <gschwartz1 at mchsi.com>
To: "Antique tractor email discussion group" <at at lists.antique-tractor.com>
Sent: Monday, April 07, 2008 8:09 PM
Subject: Re: [AT] Satellite Tracking was Warning and apology.


> Charlie & Cecil;
> Thank you for the information. I'm still trying to figure out LORAN, and
> along comes GPS. I'm hurrying but can't seem to catch up. "locating to
> within 1/10th of an inch" seems unreal but very necessary in todays world.
> Thanks a bunch for just carrying me along for the ride.
> Gil
>
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