[Action80]

...at times...

Yes, "at times". What exactly is the issue here? Isn't it really simple? Sometimes where the sky meets the land/water, whatever, that meeting point, the visual delineation between the two, is crisp, sharp as a tack. Other times, it's not. Mystery solved?

No, it isn't.

I described precisely why.

markjo wants to believe the color gradients of water appear the same when directly observed at that point and from three miles away.

They do not.

[DuncanDoenitz]

Now we're getting somewhere. 

Clear day, Observer A views the horizon 3 miles away.  Observer B is 3 miles from Observer A, on his horizon.  Neither can see the conditions. 

[Action80]

Now we're getting somewhere. 

Clear day, Observer A views the horizon 3 miles away.  Observer B is 3 miles from Observer A, on his horizon.  Neither can see the conditions.

Either you:

Just don't understand what I wrote; or,

Clearly understood and just rephrased it on purpose to represent something I claimed absolutely nowhere in the thread.

[AATW]

Many people think/believe they can see a definite line of the horizon.

But I've shown examples and I've used an edge detection tool which demonstrates that the distinction between sea and sky is clear.
Pete has claimed that it's the wrong tool, his suggestion of a colour picker makes no sense. No-one is claiming we live in a mathematically perfect world where the line would be perfect, but the distinction is clear enough.

But thats c.3 miles away. And is so fine that it isnt even the thickness of a piece of paper - and you couldnt see something that thin at 3 miles.

I showed a zoomed in picture which shows a detail of the horizon. At that scale you can see there are bumps of the waves, as you would expect. And you can see the top of a distant ship which is beyond and below the horizon. But the distinction between sea and sky is perfectly clear. You called the picture fake without providing any evidence. I also showed a video of ship disappearing below the horizon and emerging from it. Your quibble there was the timelapse stopped following one ship, which was almost completely sunken and started following another which was also mostly sunken and followed it as it came towards the camera and emerged from below the horizon. Your complaint was that the video didn't follow it as it sunk all the way, which is spurious. Why did it sink at all in your opinion?

You're free to make your own observations of course and present them.

[Pete Svarrior]

But I've shown examples and I've used an edge detection tool which demonstrates that the distinction between sea and sky is clear.

No, it does not. If your methodology demonstrates something that's false, you should seriously question your methodology. But sure, let's poke at it some more.

Using "an edge detection tool" (you didn't clarify what tool, how you set it up, or what it actually did - because you don't know any of these things) can produce the following results on a familiar image (this will of course not be an exhaustive list, just a sample):

Option 1:


Option 2:


Option 3:


Option 4:


Option 5:


Option 6:


All of these images were generated using fairly standard edge-detection algorithms, with fairly typical parameters. So, which one of them is "double-plus-good real"? Is it option 3, because it shows what you consider "obvious"? Or option 2 because it's the opposite of what you'd expect? Ooh, ooh, maybe it's option 5, which so beautifully identified the actual edge of your use of the gradient tool. You didn't even bother to place it in the middle when you produced your picture, you just wanted it to "look right".

Or maybe, just maybe, throwing a tool you don't understand at a problem is not the right solution here, especially when the tool was never designed to find what you're trying to find? Just a thought.

You might also notice that, even between different applications that did find an edge in """reality""", they found it in different places. Egads, your methodology, which was supposed to show us that locating the horizon is easy, results in... multiple possible locations of the horizon. Crazy how nature do that.

Pete has claimed that it's the wrong tool, his suggestion of a colour picker makes no sense.

You're very generous to yourself. Please try not to mix up you not understanding something with it making no sense. There are resources available out there to help you understand. This includes me - you can ask me questions instead of [checks notes...] screaming "FAAAAAAKE!" and running away.

No-one is claiming we live in a mathematically perfect world where the line would be perfect, but the distinction is clear enough.

I agree - the distinction is that your "foggy day" and "reality" (oh, why did you have to name it so...) sections show a gradient, and the "mathematical model" one does not.

Oh, wait, that's not the "clear distinction" you wanted. Huh.

[markjo]

And yet there are other times where there is no gradient of color between the water and sky or reflectivity in either medium where the distinction is quite obvious.  Don't those situations count?

You have no way of knowing what situations are present at the moment of observation, given you are three miles away.

As for knowing the conditions three miles out to sea...  Well, it's a fairly trivial thing to have someone go three miles out on a boat and report those conditions back to you via phone or radio.

They are at their point, and you are at yours. They are looking at what things look like up close, not from three miles away. Things look different.

The conditions across the three or more miles (depending on your elevation) across the sea determines what kind of view of the horizon you will get.  If you can see a nice, crisp distinction between the water and the sky (horizon), then there is a pretty good chance that the conditions across those three or more miles are pretty favorable for such observations.  However, if you have any questions about the conditions between the your position and the three or more miles in question, then you should have a trusted associate get in a boat and go out three or more miles and report the conditions along the way.  Again, if the conditions are favorable along the way, then there's a pretty good chance that the view from the boat will be pretty much the same as the view from the shore.  I'm not sure why that's so hard to understand or believe.

[Action80]

And yet there are other times where there is no gradient of color between the water and sky or reflectivity in either medium where the distinction is quite obvious.  Don't those situations count?

You have no way of knowing what situations are present at the moment of observation, given you are three miles away.

As for knowing the conditions three miles out to sea...  Well, it's a fairly trivial thing to have someone go three miles out on a boat and report those conditions back to you via phone or radio.

They are at their point, and you are at yours. They are looking at what things look like up close, not from three miles away. Things look different.

The conditions across the three or more miles (depending on your elevation) across the sea determines what kind of view of the horizon you will get.  If you can see a nice, crisp distinction between the water and the sky (horizon), then there is a pretty good chance that the conditions across those three or more miles are pretty favorable for such observations.  However, if you have any questions about the conditions between the your position and the three or more miles in question, then you should have a trusted associate get in a boat and go out three or more miles and report the conditions along the way.  Again, if the conditions are favorable along the way, then there's a pretty good chance that the view from the boat will be pretty much the same as the view from the shore.  I'm not sure why that's so hard to understand or believe.

There is no clear distinction between the water and the sky.

You can never be sure of which is which from three miles away.

I'm not sure why that's so hard to understand or believe.

Please stop making such obviously false statements.

[markjo]

There is no clear distinction between the water and the sky.

You can never be sure of which is which from three miles away.

I'm not sure why that's so hard to understand or believe.

It's hard to understand or believe because it's obviously wrong.  If you can't see where the water ends and the sky begins in this photo, then I'm not sure how much more clear the distinction needs to be to satisfy you.

I'm also not quite sure why you're hung up on three miles.  Depending on your elevation, the horizon is often far more than three miles away.

[Action80]

There is no clear distinction between the water and the sky.

You can never be sure of which is which from three miles away.

I'm not sure why that's so hard to understand or believe.

It's hard to understand or believe because it's obviously wrong.  If you can't see where the water ends and the sky begins in this photo, then I'm not sure how much more clear the distinction needs to be to satisfy you.

You are sadly wrong if you think the photo you present depicts a clear distinction, but it doesn't. Go ahead and point it out.

I'm also not quite sure why you're hung up on three miles.  Depending on your elevation, the horizon is often far more than three miles away.

I didn't introduce three miles into the discussion. RE adherents did.

Not hung up on it at all,  as I have no way of telling how far I can see out over open water if my eyes are just over 6 feet above the level where water meets the shore.

[markjo]

You are sadly wrong if you think the photo you present depicts a clear distinction, but it doesn't. Go ahead and point it out.

Ummm....  The dark blue area in the bottom half of the picture is the sea and the light blue area in the top half is the sky.  To my eyes, there is a pretty clear and distinct change from dark blue to light blue in the middle.

[Action80]

You are sadly wrong if you think the photo you present depicts a clear distinction, but it doesn't. Go ahead and point it out.

Ummm....  The dark blue area in the bottom half of the picture is the sea and the light blue area in the top half is the sky.  To my eyes, there is a pretty clear and distinct change from dark blue to light blue in the middle.

Ummm...the light blue under the clouds...what is that...water or sky...how do you know for sure...

[Pete Svarrior]

Ummm....  The dark blue area in the bottom half of the picture is the sea and the light blue area in the top half is the sky.  To my eyes, there is a pretty clear and distinct change from dark blue to light blue in the middle.

And that, my dear friend, is why we don't measure these things by looking at low-resolution pictures with the naked eye. Even in your cherry-picked example, there's a clear gradient, which you could measure, if you were interested in not being a complete waste of oxygen.

[AATW]

If your methodology demonstrates something that's false

You keep claiming this, but haven't explained why you believe it to be false.

Using "an edge detection tool" (you didn't clarify what tool, how you set it up, or what it actually did - because you don't know any of these things) can produce the following results on a familiar image

Yes. Of course you can produce different results by setting the sensitivity to different levels. I used the one in Paint.NET. I can't remember exactly what sensitivity level I set it to, I can find out if you really care.

I did an image processing course as part of my degree by the way and while that was some time ago I do remember writing a simple edge detection algorithm. I wouldn't claim to be an expert in this, but I know the basics of how they work. I'm not as ignorant about all this as you suppose. And yes, of course if you set the tool too sensitive then it won't detect the horizon line. And OK, I did set it at a level which detects the line. You got me. BUT, I don't believe that was fudging the results. In the image which shows the results of the edge detection tool the edges of the sails show as weaker lines than the horizon line. I mean...sails have edges, right? Obviously in real life objects don't have thick black outlines around them. No edge is going to be mathematically perfect. And therefore no edge detection algorithm set to detect only perfect edges is going to detect them. And that's the reason your suggestion of a colour picker makes no sense. That would work in showing the difference between two pixels which delineate a perfectly clear edge, but those don't exist in the real world.

A clear line between sea and sky, or sail and sky, or any two objects, can exist without it being mathematically perfect or being a gradual fade between one and the other. Those aren't the only two options.

the distinction is that your "foggy day" and "reality" (oh, why did you have to name it so...) sections show a gradient, and the "mathematical model" one does not.
Oh, wait, that's not the "clear distinction" you wanted. Huh.

It's not about what I want, it's about reality. There's a difference between mathematical perfection and reality.
But there is also a difference (a different difference, if you will) between observations on a foggy day when you can't see as far as the horizon, and observations on a clear day when you can.

[Pete Svarrior]

You keep claiming this, but haven't explained why you believe it to be false

Of course I did. You're just a little preoccupied repeatedly declaring your supremacy, even when it defies RET. Let me know if you ever choose to break that cycle. It might not turn you to FE, but maybe it'll make you a semi-servicable denizen of the 21st century.

Yes. Of course you can produce different results by setting the sensitivity to different levels.

Ah. But that's not what I did, and you already know that's not what I did. I pre-empted your reaction and informed you that I didn't mess with the parameters, and that I certainly didn't take them outside of reasonable defaults. Of course, you're also not a moron, so you know some of the outcomes I showed you couldn't be possible by just adjusting "sensitivity" (not that you know what that means in the context of the algorithm you chose, because you don't know what algorithm you chose, but the intuition is there).

I used the one in Paint.NET. I can't remember exactly what sensitivity level I set it to, I can find out if you really care.

Oh, I don't care. I know what you did. It's you who doesn't. But let me spoil your fun a little further - it's not just finding out what value you picked for "sensitivity" that you need to move your argument forward. You need to find out what "sensitivity" is; what the algorithm you chose does.

Before you start thinking about Zeteticism, it would be prudent for you to at least understand basic science. Plugging data into programs you don't understand and hoping they'll support your preconceived notions just ain't it.

I did an image processing course as part of my degree by the way

I'm sorry, and there really is no nice way of saying this, but - I hope you don't expect me to be impressed. I spent most of my professional life teaching undergraduates, and I have a very low opinion of the system. You might as well tell me you've been potty trained. I don't disbelieve you, but I'm not immediately swept off my feet.

I do remember writing a simple edge detection algorithm. I wouldn't claim to be an expert in this, but I know the basics of how they work. I'm not as ignorant about all this as you suppose.

And yet you keep referring to them as if there was only one. That's why I showed you the outputs of multiple edge detection algorithms, without straying away from their reasonable parameters (again, plural). I don't just say you don't know how they work for the hell of it, nor do I do it to insult you. It's just that every message you send shows that you have no idea what you're taking about, beyond maybe a couple hours of a C++ lab.

And OK, I did set it at a level which detects the line. You got me.

I didn't "get you". In fact, I assumed you didn't touch the sliders. The fact that you did simply means that I underestimated how much you meddled with a sound methodology.

BUT, I don't believe that was fudging the results. In the image which shows the results of the edge detection tool the edges of the sails show as weaker lines than the horizon line. I mean...sails have edges, right?

Another example of you showing you don't know what you're talking about. For your algorithm of choice, a thicker line would imply less confidence in edge detection. But you thought the opposite. You're just slamming data into a program you don't understand, and confidently declaring your conclusions from outputs the meaning of which you don't understand.

And that's the reason your suggestion of a colour picker makes no sense. That would work in showing the difference between two pixels which delineate a perfectly clear edge, but those don't exist in the real world.

That's because you are, fundamentally, anti-scientific. You want to find an edge. You therefore reject any method that will not find one. But I didn't tell you to look for an edge - I told you to look for a gradient. And measuring colours of adjacent pixels is a very reliable way of identifying a colour gradient - they either do smoothly change from one colour to another, or they don't. There are caveats here, of course - some of the examples shown in these thread are hilariously JPEG-crushed - but let's learn how to crawl before running a marathon, eh?

Once again, I encourage you to do science. Don't sit here farting our declarations of how wrong I am - you didn't even understand what I'm saying, you're quire a few steps away from being able to analyse whether I'm right or not. If you have questions about I propose, try the radical approach of asking them.

It's not about what I want, it's about reality.

I passionately agree. I'll be ready for you whenever you'd like to discuss reality, rather than chasing results you want.

[AATW]

You keep claiming this, but haven't explained why you believe it to be false

Of course I did.

OK, well I did find a post which wasn't a reply to me so I guess that's why I missed it.
Basically your claim is that the horizon can't be sharp because we have an atmosphere. You also said something about in RET the earth not having an edge but I don't really understand that bit. If we were on a perfect sphere with no atmosphere then the horizon would be a line - actually a circle around you - which would be the limit you could see. The radius of that circle would be determined by your viewer height. You wouldn't be able to see further than that because of the ground curving away from you. Now obviously we don't live on this mathematically perfect world, but that's still what the horizon is.

Another example of you showing you don't know what you're talking about. For your algorithm of choice, a thicker line would imply less confidence in edge detection.

Can you explain that? It's the "Strength" slider I adjusted. The higher I set that the more and thicker lines it shows as edges. As I turn it lower those lines get fewer and thinner. If you turn it all the way down then you don't get any edges at all. So how would thicker lines imply less confidence?

That's because you are, fundamentally, anti-scientific. You want to find an edge.

I don't "want" anything. In all the pictures I've posted the horizon simply looks very clear to me. An edge detection tool is a reasonable way of verifying that. You dispute that of course, but that dispute seems to revolve around the line being a perfect edge. That isn't the RE claim.

I didn't tell you to look for an edge - I told you to look for a gradient. And measuring colours of adjacent pixels is a very reliable way of identifying a colour gradient - they either do smoothly change from one colour to another, or they don't.

And what would that demonstrate? That there is no mathematical perfect edge? OK. Granted. And nor would I expect there to be. I took this photo, its of the edge of a wall as it turns a corner, beyond it looks through a window into a dark hallway, so there's a clear distinction between the wall and the view beyond it. The top below is part of the picture, the lower part is a portion of the top, zoomed in:



So...I guess my wall doesn't have an edge then. Except of course it bloody does. Whether it's JPEG compression or lack of sharpness in the image or whatever, the picture doesn't show a perfect edge. That doesn't mean the wall doesn't have an edge which an edge detection algorithm would find.

Having thought about this some more, I have come to the conclusion that the observation of the horizon wouldn't be as different as I supposed if we did live on a FE. I think that the line would be a little less clear on a FE but it's an impossible experiment to run to find out. There are of course other clues about the horizon and in particular the observations of objects beyond it which are better differentiators between the two models.

[Pete Svarrior]

Basically your claim is that the horizon can't be sharp because we have an atmosphere.

No.

I repeat my invitation: if there is something you don't understand, you can try the radical approach of asking questions.

Can you explain that? It's the "Strength" slider I adjusted. The higher I set that the more and thicker lines it shows as edges. As I turn it lower those lines get fewer and thinner. If you turn it all the way down then you don't get any edges at all. So how would thicker lines imply less confidence?

Sure! Although you're correct that adjusting the "strength" slider would result in thicker lines, that's not related to what I'm saying. Within the same run of the same algorithm, a thicker line implies a more poorly defined edge. You can see that in action in several of my examples from earlier:



Ignore the "foggy day" portion (it's useless for oh-so-many reasons), but compare the """reality""" portion to the "mathematical model". See how the gradient translates to a visibly thicker line than the sharp delineation? (Or, in one case, see how the line isn't there at all for the "mathematical model"?). Although each example uses a different algorithm, the underlying reasons for this can be grouped together. In layman's terms - we know for sure that there's a boundary between two colours somewhere in """reality""" - but determining where it is is exactly is challenging, and hugely depends on how you define it. Thicker line, less obvious edge.

And what would that demonstrate? That there is no mathematical perfect edge?

Nah. You're really fixated on this "it's either mathematically perfect, or it's not there at all" thing. It's not helping your argument.

Now, I reckon you forgot what we're talking about by now, so let me offer a quick reminder. It was your position that a sharp edge would be proof of RE, and that a gradient horizon would be indicative of FE. My position is that this is not the case - you should be expecting a gradient in both models, and therefore your argument is a waste of time. We are now stuck on you simultaneously rejecting that there is a gradient to the horizon, while repeatedly stating "well, okay, it's not mathematically perfect, but duuuuuh". In reality, there are no ifs or buts about it. Take your favourite photo of the horizon (n.b., not a wave that's less than a mile away from the photographer) and inspect the colours. They will gradually fade away, as is expected of RE and FE alike.

So...I guess my wall doesn't have an edge then. Except of course it bloody does. Whether it's JPEG compression or lack of sharpness in the image or whatever, the picture doesn't show a perfect edge.

Uuuuuuuuuuuuuurgh. Are you sure you took a course on image processing? I'm getting suspcious here. You're not looking at JPEG compression or "lack of sharpness in the image". You're looking at interpolation (probably bicubic) - if you wanted to preserve the colour gradients, you should have used nearest-neighbour.

Here's a perfect black-and-white image, followed by a small portion of the same image, but enlarged with bicubic interpolation:




You keep slamming your head against tools you don't know the first thing about. That's not how you science.

Here's what happens if you enlarge your door/wall photo with the right tool for the job.



Gosh, look at that! There's hardly any gradient at all! And it would have been sharper if the initial image wasn't of arse quality. Of course, you could have just used a colour picker like I told you to aeons ago, but whit kan a man dae?

[stack]

Instead of it being about whether the horizon line is crisp or a gradient, isn't it more about the horizon line, fuzzy or not, and where it is in our field of view? As in some FE contend that the horizon line would and always rises to eye-level whereas GE contends that it dips below eye-level with altitude...

[Gonzo]

So if you see bumps of waves where is the exact line? At the peak or the trough of the waves? If so which ones? Some are bigger than others.

If we're getting to this level of detail, its a median line between the peaks and troughs.  The volume of water present above the median is equal to the volume absent below the line.  The position of the median is a function of gravity, the shape of the Earth, and the volume of water on the Earth.  Waves are principally a localised topical effect of wind; past, and present. 

@Gonzo; by my count that's 3 individuals who have failed to respond to your question.  Its difficult to respond to someone's opinion on a phenomenon (in this case the maritime horizon), when we don't know whether they are actually in a position to observe it directly.  (Or, indeed, if they've ever observed it directly).

Quite.

It’s rather a habit of some people.

I haven’t posted recently as I’m on holiday in the Isle of Skye, Scotland, I’m staying in a cottage literally a few metres from the sea. On clear days I can see a very obvious clear delineation between sea and sky.

[Gonzo]

Yes, often times, the sea and sky are indistinguishable.  The other half of that equation is that often times the difference is like night and day. 

If you haven't observed this yourself, perhaps you need to get out more.

Whether or not I 'need to get out more," is not the point. You, nor anyone else for that matter, have zero ability to determine the precise conditions of any object from three miles away. Especially with the naked eye.

That's the point.

We weren’t talking about how far away the horizon was. We were saying that it was often very clear. Because it is. I can count on the fingers of one hand how many times a year I used to struggle to see a clear horizon in good visibility.

You couldn't plot with any accuracy the exact line of the horizon from 3 miles away. Even if you did manage to wade thogh the swell, waves, freak waves, refraction, haze, reflections.

And on a clear day, with little swell or chop, lo and behold it’s still a clear line.

I really don’t understand how people can say it’s not. I spent the first 18 years of my life looking at the horizon out to sea literally hundreds of times every day.

Do you live near the coast, SimonC?

Just because someone has done something for a number of years does not mean they have been doing it right. Practice doesnt make perfect. Practice makes permanent. My heating engineer had been using an old saw to cut coper pipe since he was an apprentice. He had no idea that modern day pipe cutters had been invented and carried on blissfully with his 'rough' and time-consuming jointing method.
Many people think/believe they can see a definite line of the horizon. But thats c.3 miles away. And is so fine that it isnt even the thickness of a piece of paper - and you couldnt see something that thin at 3 miles.

Not doing it right?

I’m looking at the horizon and can see a clear delineation of the sea and sky. It’s quite simple. I’m doing it right now, as I type. It’s not thin, it’s the boundary between sea and sky, as you look out.

If you hold two pieces of paper of different colours and overlap one on top of the other, there’s not a thin, invisible line separating them, it’s where the extent one of piece of paper stops, and the other continues behind, and therefore becomes visible. One large body is in front of another large body. On days of poor weather, where the visibility is low, the clear delineation is not there, the sea appears to gradually disappear into the mist.

How you often looked out to sea? Are you saying you never see a clear delineation between sea and sky?

[Gonzo]

And on a clear day, with little swell or chop, lo and behold it’s still a clear line.

I really don’t understand how people can say it’s not.

You can keep making this false statement until the end of time (if you choose), but I have already pointed out why it is false.

Can you explain what you mean? Because I don’t think you have.

On a clear day with good visibility, the delineation between sea and sky is very easy to discern.

Have you lived on the coast? How often do you look out to sea on the average day?