Offline SteelyBob

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Wiki on aviation
« on: March 08, 2022, 09:49:25 PM »
The wiki has a small section on 'aviation', in which it quotes from, amongst other things, a flight dynamics book which lists a set of assumptions:



The wiki introduces this by saying:
Quote
Discussion on this topic revolves around the assertion that aircraft instrumentation are built to assume, and pilots are taught to fly, over a flat, non-rotating earth.

...and concludes it by saying:
Quote
Note: The document does not go on to "unsimplify," to give its students accurate dynamics. The word 'coriolis', for instance, appears a single time.

Is anybody actually seriously holding this up as proof of a FE? If you are an ardent FE believer then the first two assumptions are clearly something you believe to be true anyway, but the second two are demonstrably false. Aircraft are not of constant mass (they burn fuel and become lighter) and they are not rigid (as anybody who has observed the wings on an airliner bending will know). The list is therefore quite clearly, as it says itself, simplifying reality for the purposes of building a useful mathematical model of flight - mass changes can be neglected because they are relatively slow with respect to time and therefore don't effect the dynamics of flight. The earth can be treated as flat because, from a short-term modelling perspective, it makes very little difference.

Introduce navigation, and things get very different, just as if you want to discuss aerodynamic flutter, for example, then the rigidity assumption goes out the window. The assertion that instruments are built to assume a flat earth is demonstrably false - gyro based nav systems, for example, have to correct for transport and rotation errors. Likewise pilots are taught about globe navigation, great circles etc at an early stage in training.


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Offline Tom Bishop

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Re: Wiki on aviation
« Reply #1 on: March 08, 2022, 10:04:24 PM »
Quote from: wiki
Discussion on this topic revolves around the assertion that aircraft instrumentation are built to assume, and pilots are taught to fly, over a flat, non-rotating earth.

Quote from: SteelyBob
The earth can be treated as flat

It sounds like you are supporting the premise of that Wiki page, that pilots are taught to fly over a FE, as demonstrated in that guide from a flight dynamics course.

Quote from: SteelyBob
Is anybody actually seriously holding this up as proof of a FE?

Where does it say proof? It's an interesting point of aviation. The rest of that Wiki page cites many more examples in which the earth is treated as flat, including in military missile dynamics.

« Last Edit: March 08, 2022, 10:22:21 PM by Tom Bishop »

Offline jimster

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Re: Wiki on aviation
« Reply #2 on: March 08, 2022, 10:40:15 PM »
I told my software engineer friend about FE. He told me he was the programmer who wrote the routing software for the Canadian Air Traffic Control System. The US uses airways, set routes like interstates. The Canadians wanted to route their planes straight from departure airport straight to the destination for each airplane (routing around collisions, of course). He wrote the program that figured out the distance and direction. He said he used the spherical geometry equations straight out if a textbook and they worked perfectly. Obviously, they did much qa, and the system has been in use for decades, many planes arrive where they intended to go daily. If the earth was flat, the equations would be wrong and the pilots would not find an airport where the software sent them. The longer the route, the more the difference.

You can do this yourself, actually. Do the spherical trig math to calculate the distance between two cities, for Tom Bishop, make that two cities on the same land mass, perhaps Beijing and Madrid. For some reason, Tom Bishop thinks gps doesn't work over water. The RE 3d trig answer will match google maps, airline schedule, time/speed/distance of airliner flight, lat/long per wikipedia, etc, and no evidence at all for the FE distance calculation, whatever that might be.

Find a discrepancy between any RE info sources or the math calculations and prove FE! I will be your disciple. And I will make a lot better video than the one you just posted. His production values, scripting, delivery, etc is just bad regardless of the truth of his content. FYI, this maybe shouldn't matter, but it does. People are more likely to believe well made videos, at least most people. Perhaps FEs perceive truth in amateurish, clearly non-expert videos.
"Electromagnetic Acceleration" sounds so much more sciency than "bendy light".

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Offline Tom Bishop

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Re: Wiki on aviation
« Reply #3 on: March 08, 2022, 10:55:13 PM »
Quote from: jimster
I told my software engineer friend

Sure you did.

Quote from: jimster
People are more likely to believe well made videos, at least most people. Perhaps FEs perceive truth in amateurish, clearly non-expert videos.

I really doubt that amateurs wrote the documents presented in the video.
« Last Edit: March 08, 2022, 11:01:48 PM by Tom Bishop »

Offline jimster

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Re: Wiki on aviation
« Reply #4 on: March 08, 2022, 11:15:41 PM »
Pilots say they are flying level when they are flying at constant altitude. The curvature is ignored for aspects that are local, and they talk as though the earth is flat for convenience. Curvature of the earth mainly needs to be considered for navigation, just as he read. Locally, FE = RE or close enough. At 1000 miles, big difference.


https://www.youtube.com/watch?v=bRay2R9S0GU


"Electromagnetic Acceleration" sounds so much more sciency than "bendy light".

Re: Wiki on aviation
« Reply #5 on: March 09, 2022, 12:06:03 AM »
Of course effects not large enough to make any difference in a particular situation are ignored.   When judging whether you need to fill up your car's tank to get to a particular destination do you account for the humidity?  It does make a difference but of course not remotely big enough of one to worry about when deciding to go to the store first or the gas station first.   When learning to fly the focus is on controlling the plane and it will be quite a while before you fly even out of sight of the airport from which you took off.  Why would dealing with great circle routes etc make any sense in that situation?  Continue on to the point of planning trips of 1000s of miles and new things will have to be considered.  This is the same as the fact that NASA uses Newtonian mechanics to fly around the solar system despite knowing that the more accurate description is special and general relativity.  But start dealing with the clocks in GPS satellites and relativity must be considered.  Isn't all that obvious?
If "bendy light" were real the spot shape and power output of large solid-state lasers would vary depending on their orientation relative to the surface of the earth, but this is not observed thus bendy light is not real.

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Offline Tumeni

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Re: Wiki on aviation
« Reply #6 on: March 09, 2022, 11:22:37 AM »
Why would the assumptions need to be made, if the conditions in those assumptions are already satisfied?

If the Earth is ALREADY flat, why would this need to be specified as a "simplifying assumption" ?
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Offline SteelyBob

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Re: Wiki on aviation
« Reply #7 on: March 09, 2022, 12:33:54 PM »
Quote from: wiki
Discussion on this topic revolves around the assertion that aircraft instrumentation are built to assume, and pilots are taught to fly, over a flat, non-rotating earth.

Quote from: SteelyBob
The earth can be treated as flat

It sounds like you are supporting the premise of that Wiki page, that pilots are taught to fly over a FE, as demonstrated in that guide from a flight dynamics course.

Well, let's get our facts straight here, as you seem to be confusing a few things. That flight dynamics course is not for pilots, but rather undergraduate aeronautical engineers. It goes far, far deeper into flight dynamics than any pilot training course would. You won't find may pilots conversant with eigenvalues, for example. Moreover, that specific course is for a very specific thing - modelling aircraft behaviour over short time periods. To model the earth as round would make for far, far more complex equations, without adding any real value to the models. The same is equally true for modelling mass changes due to fuel burn, or the distortions of the wings and fuselage as the aircraft manoeuvres. Both of those things happen, just as the earth is spherical, but there is no value in the effort required to model them in the context of the subject being discussed. For other subjects, such as long-range performance, the situation is clearly very different, and appropriate modelling assumptions need to be made.

Locally speaking, for most human activities, the earth might as well be flat. This is not evidence of the earth actually being flat; it's just a consequence of the very large ball we live on compared to our size as humans living on it. It looks exactly as you would expect it to look if you are 6 feet tall living on a 25,000 mile circumference ball.

Quote from: SteelyBob
Is anybody actually seriously holding this up as proof of a FE?

Where does it say proof?
Well, aside from the title of the video you posted immediately below this question, and in the link on the page we are discussing, I had rather assumed that, given it was in the 'Flat Earth wiki', you were using it in your evidence pile for reasons the earth is flat, just as the creator of the video you linked to is doing.

It's an interesting point of aviation. The rest of that Wiki page cites many more examples in which the earth is treated as flat, including in military missile dynamics.

 Interesting, indeed, but if you don't acknowledge that the people using the flat earth assumption don't actually think the earth is flat then you are being dishonest with your work.



This video is unbelievably, terribly bad - I'm surprised you're associating yourself with it. I watched a few snippets:

 - the discussion around Tomahawk versus SAM engagements. This is just, again, a complete twisting of a simplifying assumption with it being some evidence of a FE. The ranges involved in a SAM versus cruise missile are trivial compared to the curvature of the earth. A flat earth model is therefore completely reasonable. Note the other assumptions made - straight and level flight (despite the fact that cruise missiles manoeuvre), level terrain, one missile per engagement - these are all simplifying assumptions. They are not necessarily what occurs in the real world.

- at 17:15 he angrily rants about a similar flight model to the one linked to in the wiki. He keeps saying 'a rigid aircraft of constant mass', seemingly oblivious to the fact that aircraft are not actually rigid, and they aren't of constant mass either, and the world isn't flat, but all three make for much simpler calculations when you're designing aircraft. He rants on about challenging a 'glober' to find a paper where flight dynamics are modelled using a round earth. That ain't gonna happen, because it would be a ridiculous piece of work. If you're modelling a short period oscillation, or dutch roll, or some other aspect of stability or control, then the tiny, tiny shift in the weight vector as the aircraft moves a few hundred metres around the planet would make a ludicrously small difference to the answers obtained, despite it causing a major, major headache in terms of complexity. Citing this as evidence for the earth being flat merely betrays a lack of understanding of the specific subject, as well as science in general.

- He undermines his own argument later on, and indeed yours, when he looks at the text around 21:00 onwards - it gives a great example of the limitations of a flat earth assumption. It's fine for short range activities, but when you need to consider longer distances, the flat earth assumption can no longer be used. That is staring him in the face - he even highlights it himself (25:00) - he seems to try to wave it away but to be honest his argument was somewhat incoherent and it's not really clear what he's trying to say.


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Offline Tom Bishop

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Re: Wiki on aviation
« Reply #8 on: March 09, 2022, 02:09:57 PM »
Quote from: SteelyBob
Well, let's get our facts straight here, as you seem to be confusing a few things. That flight dynamics course is not for pilots, but rather undergraduate aeronautical engineers.

Did I say that the document was for pilots, or did I say it supported it? Please engage in reading comprehension. The fact that the plane is built to fly over an FE supports the ideas and premise given in the page that pilots are taught to fly on an FE. The premise in the Wiki also includes the engineering: "Discussion on this topic revolves around the assertion that aircraft instrumentation are built to assume, and pilots are taught to fly, over a flat, non-rotating earth."

Quote from: SteelyBob
Locally speaking, for most human activities, the earth might as well be flat. This is not evidence of the earth actually being flat; it's just a consequence of the very large ball we live on compared to our size as humans living on it. It looks exactly as you would expect it to look if you are 6 feet tall living on a 25,000 mile circumference ball.

Considering that aircraft navigation and engineering is often given as evidence for a RE in these discussions, and it is assumed that planes and missiles and supersonic jets account for curvature and Coriolis, your comment rejects this notion as false.

Quote from: SteelyBob
Well, aside from the title of the video you posted immediately below this question, and in the link on the page we are discussing, I had rather assumed that, given it was in the 'Flat Earth wiki', you were using it in your evidence pile for reasons the earth is flat, just as the creator of the video you linked to is doing.

The Wiki doesn't call much of anything it cites as "proof". This is your own assumption and interpretation.

Also, the creator of that video did not write the Wiki. The commentary of the Wiki is not that author's. You are wrong there. If the Wiki links to something of related interest in its "Related References" section, and that author of that external content calls proof, it does not mean that the Wiki is actually doing so. Please apply some reading comprehension before wildly assuming things.

Quote from: SteelyBob
Interesting, indeed, but if you don't acknowledge that the people using the flat earth assumption don't actually think the earth is flat then you are being dishonest with your work.

I don't see any reason to include that many of the sources from contemporary academia cited the Wiki cited believe in RE. That should be obvious to most people. Sorry that you had a tough time figuring that out.

Quote from: SteelyBob
- the discussion around Tomahawk versus SAM engagements. This is just, again, a complete twisting of a simplifying assumption with it being some evidence of a FE. The ranges involved in a SAM versus cruise missile are trivial compared to the curvature of the earth.

If you had bothered to research it you would have found that the Tamahawk cruise missile discussed in the video at the 11 minute mark has an accuracy of about 5 meters and range of about 1,500 miles.



Too short and too inaccurate to be affected by earth curvature, I'm sure.  ::)

Quote from: SteelyBob
He rants on about challenging a 'glober' to find a paper where flight dynamics are modelled using a round earth. That ain't gonna happen, because it would be a ridiculous piece of work.

Anyone can see that a missile with a range of 1,500 miles and an accuracy of 5 meters will be affected by the curvature of the Earth. That you think it is unnecessary to account for the curvature of the earth is a ridiculous position. Quite obviously a levelly flying missile is continuously gaining altitude as the earth curves away, and that would need to be accounted for to maintain such range and accuracy.

Your response to a request to show that such things are actually using curvature is "ain't gonna happen", and is a ridiculous failure to support your position.
« Last Edit: March 09, 2022, 03:07:38 PM by Tom Bishop »

Offline SteelyBob

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Re: Wiki on aviation
« Reply #9 on: March 09, 2022, 03:17:46 PM »
Quote from: SteelyBob
Well, let's get our facts straight here, as you seem to be confusing a few things. That flight dynamics course is not for pilots, but rather undergraduate aeronautical engineers.

Did I say that the document it was for pilots, or did I say it supported it?

You said:
Quote
that pilots are taught to fly over a FE, as demonstrated in that guide from a flight dynamics course.

That's not a course for pilots. It matters not, to be honest - I just thought you might be open-minded and interested in accuracy / learning something new rather than just being defensive.

Quote from: SteelyBob
Locally speaking, for most human activities, the earth might as well be flat. This is not evidence of the earth actually being flat; it's just a consequence of the very large ball we live on compared to our size as humans living on it. It looks exactly as you would expect it to look if you are 6 feet tall living on a 25,000 mile circumference ball.

Considering that aircraft navigation and engineering is often given as evidence for a RE in these discussions, and it is assumed that planes and missiles and supersonic jets account for curvature and Coriolis, your comment supports the notion that this is false.

Yes, aircraft navigation is often given as evidence for RE, as are things like gyro systems. And those things cannot use a flat earth assumption, as indeed described by the evidence presented in the video you yourself linked to. This is really simple stuff - if it's short time frames or short ranges, then FE is a valid simplifying assumption. If the time period is long, or the ranges large, then it isn't. Do you understand that concept?

Quote from: SteelyBob
- the discussion around Tomahawk versus SAM engagements. This is just, again, a complete twisting of a simplifying assumption with it being some evidence of a FE. The ranges involved in a SAM versus cruise missile are trivial compared to the curvature of the earth.

If you had bothered to research it you would have found that the Tamahawk cruise missile discussed in the video at the 11 minute mark has an accuracy of about 5 meters and range of about 1,500 miles. Too short and too inaccurate to be affected by earth curvature, I'm sure.  ::)

Well aware of Tomahawk performance, thanks. Again, you are embarrassing yourself by wading into territory you clearly don't understand properly. I'll say it again - we are talking about a SAM engaging a cruise missile - the range of the cruise missile in that context is irrelevant. The limiting factor is the range of the SAM and the detection range of the controlling radar. Depending on the systems involved, those ranges are likely to be single digit or low double digit numbers of miles - hence the flat earth assumption being valid.

As the text quoted in the video points out, if you wish to understand cruise missile guidance over long ranges, then you can't assume a flat earth.

Offline Gonzo

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Re: Wiki on aviation
« Reply #10 on: March 09, 2022, 06:36:11 PM »
Tom, can I ask what your professional experience within aviation consists of?

You do understand that flight dynamics, when applied to an aircraft, is concerned with the stability, and movement, of a body along three axes due to the changing angle of attack to the airflow.

The influence of the shape of the earth at this level is neglible.

In aviation, we make lots of assumptions to simplify things in order to focus on the important areas being studied at the time. When studying flight dynamics, one might assume the earth is flat. When starting to study radar theory, one might assume all aircraft reflect the same amount of radar energy (spoiler, this isn't true either!). In many cases we assume the air is the International Standard Atmosphere, within which are several other assumptions of air pressure, density, temperature, adiabatic lapse rate etc. This doesn't mean we believe the air pressure across the whole earth at sea level is 15 degrees celsius, nor that the air pressure across the whole earth at sea level is 1013.25hPa.

Quote
that pilots are taught to fly over a FE, as demonstrated in that guide from a flight dynamics course.

Are you a pilot? I've never been taught or told that the earth is flat in any of my training to be a pilot, or an air traffic controller, nor have I trained that to any of my trainees over the past 23 years.
« Last Edit: March 09, 2022, 10:12:13 PM by Gonzo »

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Offline Tumeni

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Re: Wiki on aviation
« Reply #11 on: March 09, 2022, 06:42:21 PM »
" The fact that the plane is built to fly over an FE supports the ideas and premise given in the page that pilots are taught to fly on an FE. "

No, it's a book on flight dynamics, not a "how-to" for plane construction. Reading up on flight dynamics does not equate with being "taught to fly"

Learning the dynamics of how a car reacts to camber, change of direction etc. does not equate with learning how to drive, nor with build techniques.
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Offline jimster

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Re: Wiki on aviation
« Reply #12 on: March 09, 2022, 07:26:23 PM »
Tom Bishop,

I want to tell you a bunch of confirmable details on who my friend is and how I know he told the truth, but I do not want to revesal private info so you can see who he is, I don't do that on the internet for obvious general reasons.

Canadian Automated Air Traffic System, known as CAATS, was developed by Hughes Aircraft of Canada, Systems Division (HCSD) (acquired by Raytheon Systems Canada Ltd. in 1997) for NAV CANADA, and MDA was subcontracted by HSCD in 1993. CAATS automates flight data processing between all major air traffic control facilities, managing flight traffic over 5.8 million square miles of Canadian airspace. The CAATS system provides the air traffic controller with all radar, flight data, weather and other information on integrated, high-performance workstations.

Even if I am making it up (I'm not), there are programming departments all around the world doing geolocation programs, navigation programs, etc. They are either using RE equations or FE equations. One of the two gives wrong answers. CAATS is one of them.

"Electromagnetic Acceleration" sounds so much more sciency than "bendy light".

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Offline stack

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Re: Wiki on aviation
« Reply #13 on: March 09, 2022, 07:42:44 PM »
The rest of that Wiki page cites many more examples in which the earth is treated as flat, including in military missile dynamics.

From the same document the video cites: "The user is responsible for entering the three-dimensional target trajectory and missile radar operating modes. Additionally, the user may select site-specific terrain or a flat-Earth representation . If a site-specific terrain is selected, the Digital Terrain Elevation Database (DTED) is used."

Looking up DTED it states: "DTED (or Digital Terrain Elevation Data) is a standard of digital datasets which consists of a matrix of terrain elevation values, i.e., a Digital Elevation Model. This standard was originally developed in the 1970s to support aircraft radar simulation and prediction. Terrain elevations are described as the height above the Earth Gravitational Model 1996 (EGM96) geoid, not the WGS84 reference ellipsoid.[1]"
https://en.wikipedia.org/wiki/DTED

So it looks like if one were to do a straight-up simulation, flat terrain is employed. If one were to select an actual target, a globe Earth (EGM96 Geoid) is used.

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Offline Tom Bishop

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Re: Wiki on aviation
« Reply #14 on: March 09, 2022, 11:04:53 PM »
The rest of that Wiki page cites many more examples in which the earth is treated as flat, including in military missile dynamics.

From the same document the video cites: "The user is responsible for entering the three-dimensional target trajectory and missile radar operating modes. Additionally, the user may select site-specific terrain or a flat-Earth representation . If a site-specific terrain is selected, the Digital Terrain Elevation Database (DTED) is used."

Looking up DTED it states: "DTED (or Digital Terrain Elevation Data) is a standard of digital datasets which consists of a matrix of terrain elevation values, i.e., a Digital Elevation Model. This standard was originally developed in the 1970s to support aircraft radar simulation and prediction. Terrain elevations are described as the height above the Earth Gravitational Model 1996 (EGM96) geoid, not the WGS84 reference ellipsoid.[1]"
https://en.wikipedia.org/wiki/DTED

So it looks like if one were to do a straight-up simulation, flat terrain is employed. If one were to select an actual target, a globe Earth (EGM96 Geoid) is used.

Is there any evidence that the geoid is actually a 3D sphere?

On NASA's site for the Earth Gravitational Model 1996 - https://cddis.nasa.gov/926/egm96/egm96.html click on "View the EGM96 geoid." at the bottom

The link is dead, but archive.org shows that the "geoid" is a Mercator projection:

https://web.archive.org/web/20010608115920/http://164.214.2.59/GandG/images/ww15mgh2.gif



The "geoid" is merely the "known" idea that the Earth is a globe, not any kind of 3D spherical model.

Also, the quote you posted is talking about SAMs, not the Tomahawk Cruise Missile.

Full quote from the document:



How typically deceptive that you would see that I am talking about the Tomahawk Cruise Missile in my comments and reply with a citation about a different kind of missile.
« Last Edit: March 09, 2022, 11:36:27 PM by Tom Bishop »

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Offline Tom Bishop

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Re: Wiki on aviation
« Reply #15 on: March 09, 2022, 11:11:38 PM »
That's not a course for pilots.

Fortunately I didn't say it was a course for pilots. I merely said that it supported it.

Quote
This is really simple stuff - if it's short time frames or short ranges, then FE is a valid simplifying assumption. If the time period is long, or the ranges large, then it isn't. Do you understand that concept?

The Tomahawk's 1500 miles isn't a long enough range?

Quote
Well aware of Tomahawk performance, thanks. Again, you are embarrassing yourself by wading into territory you clearly don't understand properly. I'll say it again - we are talking about a SAM engaging a cruise missile - the range of the cruise missile in that context is irrelevant.

If the Tomahawk isn't accounting for curvature, and there is curvature, I don't see how it can run precision maneuvers against SAMS hundreds of miles away without knowing where it is above the earth.
« Last Edit: March 09, 2022, 11:29:26 PM by Tom Bishop »

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Offline stack

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Re: Wiki on aviation
« Reply #16 on: March 09, 2022, 11:21:13 PM »
The rest of that Wiki page cites many more examples in which the earth is treated as flat, including in military missile dynamics.

From the same document the video cites: "The user is responsible for entering the three-dimensional target trajectory and missile radar operating modes. Additionally, the user may select site-specific terrain or a flat-Earth representation . If a site-specific terrain is selected, the Digital Terrain Elevation Database (DTED) is used."

Looking up DTED it states: "DTED (or Digital Terrain Elevation Data) is a standard of digital datasets which consists of a matrix of terrain elevation values, i.e., a Digital Elevation Model. This standard was originally developed in the 1970s to support aircraft radar simulation and prediction. Terrain elevations are described as the height above the Earth Gravitational Model 1996 (EGM96) geoid, not the WGS84 reference ellipsoid.[1]"
https://en.wikipedia.org/wiki/DTED

So it looks like if one were to do a straight-up simulation, flat terrain is employed. If one were to select an actual target, a globe Earth (EGM96 Geoid) is used.

Is there any evidence that the geoid is actually a 3D sphere?

On NASA's site for the Earth Gravitational Model 1996 - https://cddis.nasa.gov/926/egm96/egm96.html click on "View the EGM96 geoid." at the bottom

The link is dead, but archive.org shows that the "geoid" is a Mercator projection:

https://web.archive.org/web/20010608115920/http://164.214.2.59/GandG/images/ww15mgh2.gif



Yes, you are correct, that is a Mercator projection. Mercator projection is a "projection" from a globe:



As for a 3d representation, from your original link:

EGM96 Geoid

30'x30' value of the geoid undulations from EGM96 to 360x360. The image is shown on a Robinson projection of the Earth. Geoid undulations from N. Pavlis (RITSS/NASA GSFC), and image courtesy of J. Frawley (NASA GSFC)>

N.Pavlis also has the 3D representation of the Geoid (2008):


Geoid height, computed from the gravity field model EGM2008 (Pavlis et al., 2012).

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Offline Tom Bishop

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Re: Wiki on aviation
« Reply #17 on: March 09, 2022, 11:22:32 PM »
It says that the last 3D model you posted is "computed from" the gravity field model. It's not actually a 3D spherical model.
« Last Edit: March 09, 2022, 11:28:10 PM by Tom Bishop »

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Offline Tumeni

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Re: Wiki on aviation
« Reply #18 on: March 09, 2022, 11:35:36 PM »
It says that the last 3D model you posted is "computed from" the gravity field model. It's not actually a 3D spherical model.

So ....

How would someone make a 3D Spherical Model such that it would satisfy you (since you're not happy with one computed as above), and which could be rendered in viewable form on your computer screen?
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Not Flat. Happy to prove this, if you ask me.
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Nearly all flat earthers agree the earth is not a globe.

Nearly?

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Offline stack

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Re: Wiki on aviation
« Reply #19 on: March 09, 2022, 11:37:37 PM »
It says that the last 3D model you posted is "computed from" the gravity field model. It's not actually a 3D model.

I don't know what you mean. The DTED (or Digital Terrain Elevation Data) used for specific targets uses the EGM96 Geoid, which, in turn, was created from a Gravity field model. You're depiction of the Geoid is a mercator projection. Mercator projections come from a globe source. Not to mention, a gravity model. There's no mystery there.

As far as your comment regarding SAMS versus Tomahawks, I'm not sure why that matters. Looks like SAMS uses IMARS and Tomahawks use TRAMS (TECHNICAL RADAR ANALYSIS MODELING SYSTEM). Again, the document that was in the video references, regarding the Tomahawk TRAMS:

"The simulations use radar range equations to determine the radar performance. Included in the model are multipath calculations, clutter effects, attenuation, and detailed antenna representation. The flyby simulation incorporates the option to use either digitized terrain information from the Digital Terrain Elevation Database (DTED) provided by the Defense Mapping Agency or a simple spherical Earth model."

So the Tomahawk, using TRAMS, utilizes the same DTED Geoid as the SAMS IMARS or a "simple spherical Eath model".