Level?

[dlockhart]

[KFC911]

I prefer a level headed female....

Originally Posted by Zeke

Even small lakes follow the curvature of the earth. Thinking theoretically, if one had a level capable of seeing a highway built exactly level, it would rise as a tangent to the curvature of the earth. The earth curves 7.68" per mile. So a dead level highway a 1000 miles long would be 768 feet high at the far end.

Dead level Los Angeles to Las Vegas and you could just about step out of your car at the penthouse of the MGM Grand. (not quite — 230 feet vs. the total height of the MGM at 293.)

No wonder I can never quite get my trim to look right.

[wswartzwel]

Originally Posted by herr_oberst

Will we be seeing a This Old Swartzwel channel soon?

Nope... LOL... Tony has that covered very well.

[herr_oberst]

Originally Posted by Zeke

Dead level Los Angeles to Las Vegas and you could just about step out of your car at the penthouse of the MGM Grand. (not quite — 230 feet vs. the total height of the MGM at 293.)

Try 'splaining THAT little factoid to the flat-earthers.

[wdfifteen]

Originally Posted by Zeke

Even small lakes follow the curvature of the earth. Thinking theoretically, if one had a level capable of seeing a highway built exactly level, it would rise as a tangent to the curvature of the earth. The earth curves 7.68" per mile. So a dead level highway a 1000 miles long would be 768 feet high at the far end.

Dead level Los Angeles to Las Vegas and you could just about step out of your car at the penthouse of the MGM Grand. (not quite — 230 feet vs. the total height of the MGM at 293.)

So a perfectly accurate level could be curved.

[dad911]

Originally Posted by wdfifteen

So a perfectly accurate level could be curved.

A platform to align and corner balance a 4 wheel vehicle can be coplaner.

If you want to corner balance the banana splits banana buggy, the platform should be curved.

There is a difference between level & coplaner. In the example above, if the coplaner road is level at LA, it will not be level in Las Vegas.

I hope there are no "flat earther" surveyors/engineers out there.

[Jeff Higgins]

Originally Posted by madcorgi

It's pretty important when wings are being screwed onto big airplanes. Mr. Higgins would know this better than me, so he can chime in.

When I worked on the 777 program, one of the sections I procured was the wing root area (section 44 and the keel beam, for Boeing folks), which were mated to Boeing-built wings, where tiny variations at the mating surfaces could put the wings pretty far off "even," which was a bad thing for a lot of reasons. This was the first digitally designed airplane, and there were targets outboard at some distance and at the tip that were laser measured within some really tight tolerance. I watched the first wing-to-body join happen on 001 and watched them hit the targets perfectly. Mighty impressive for parts designed and built 9000 miles apart by several different companies.

The key was that everybody measured things from common reference points, all called out from a level nominal point. Also--everybody used the same units of measure, which is another pretty important constant.

When I first started there, we used simple surveyors' instruments - optical levels and transits - for this kind of thing. By the time I retired, we were using laser trackers. One of my responsibilities on any major airframe repair, as the tooling engineer, was to "shoot" the airplane periodically as it was torn apart, and again as it was being reconstructed, to ensure straightness and level.

There are locations of know value for station, waterline, and buttline that are marked with "golden rivets" that we "shoot" to get out values. I would have to figure jacking loads to twist the airframe back into shape as we removed and replaced large body panels, wing panels, or whatnot. Fun stuff.

[Zeke]

Originally Posted by wdfifteen

So a perfectly accurate level could be curved.

Absolutely. If you could build a perfectly flat pool table as big as a football field, the balls reaching the ends would have a tendency to slow down more than ones moving towards the center. Thinking in the extreme, balls at the end of the table would be pulled by gravity to roll towards the center. That would have to be on a theoretical table with no resistance, e.g., no felt.

A correct pool table that size would have a crown, but it would be minuscule. I see no practical reason to take in account of the earth's curvature unless launching satellites. I was just being silly about a "flat lake."

But it's true. Being as how Lake Tahoe is at a little over 21 miles in length, if you could get your eyes right at the water's surface you wouldn't see the first few inches of the shore at water's edge. It would be roughly 6+ feet at each end that you couldn't see if you were dead center.

[Jeff Higgins]

Originally Posted by Zeke

Absolutely. If you could build a perfectly flat pool table as big as a football field, the balls reaching the ends would have a tendency to slow down more than ones moving towards the center. Thinking in the extreme, balls at the end of the table would be pulled by gravity to roll towards the center. That would have to be on a theoretical table with no resistance, e.g., no felt.

A correct pool table that size would have a crown, but it would be minuscule. I see no practical reason to take in account of the earth's curvature unless launching satellites. I was just being silly about a "flat lake."

But it's true. Being as how Lake Tahoe is at a little over 21 miles in length, if you could get your eyes right at the water's surface you wouldn't see the first few inches of the shore at water's edge. It would be roughly 6+ feet at each end that you couldn't see if you were dead center.

Yeah, it's funny how "simple" definitions like "flat" really aren't. Fun stuff.

Reminds me of one of the oldest engineering jokes:

A group of engineering students and math students are posed a hypothetical question:

The football team is stood at one end of the field, and the cheerleaders are stood at the other end. Every time the ref blows his whistle, they each move half the distance to the other. How many blows on the whistle until they touch?

The math students answer that, theoretically, they never will. The engineering students answer that after four or five blows, they will be close enough...

[pwd72s]

Originally Posted by Zeke

Even small lakes follow the curvature of the earth. Thinking theoretically, if one had a level capable of seeing a highway built exactly level, it would rise as a tangent to the curvature of the earth. The earth curves 7.68" per mile. So a dead level highway a 1000 miles long would be 768 feet high at the far end.

Dead level Los Angeles to Las Vegas and you could just about step out of your car at the penthouse of the MGM Grand. (not quite — 230 feet vs. the total height of the MGM at 293.)

A retired CPO friend once told me that the curvature is used when aiming big guns...especially battleships.

May he RIP...he had no funeral here, but had his ashes spread at sea courtesy of the USN. He'd participated in those ceremonies, wanted the same when his time came.