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Offline Bobby Shafto

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Re: The Horizon is Always at Eye Level
« Reply #300 on: May 22, 2018, 09:56:37 PM »
Clear horizon!
I don’t have my toys with me, unfortunately.
But I do have the Hunter Research theodolite app. I’ll see if I can’t collect some observations at various elevations from sea level to 400’.

Max_Almond

Re: The Horizon is Always at Eye Level
« Reply #301 on: May 22, 2018, 11:13:37 PM »
Be sure to calibrate it right: bloody difficult, I found.

Best way seemed to be at sea level and set it to zero with the horizon there.

It may not give you perfectly accurate angles, but it will reflect perfectly that the angle you look down to the horizon at increases in tandem with your elevation.
« Last Edit: May 22, 2018, 11:55:11 PM by Max_Almond »

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Offline Bobby Shafto

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Re: The Horizon is Always at Eye Level
« Reply #302 on: May 23, 2018, 12:08:49 AM »
Be sure to calibrate it right: bloody difficult, I found.

Best way seemed to be at sea level and set it to zero with the horizon there.

It may not give you perfectly accurate angles, but it will reflect perfectly that the angle you look down to the horizon at increases in tandem with your elevation.
You're right. I had calibrated it yesterday, but today the roll angle was way off. Pitch angle looked like what I'd expect (for a globetard), but if there's anything wonky, I don't want to submit it for inspection.

The elevation numbers are all off too, by a consistent amount. I'm going to assume elevations are coming from GPS, so I figure they are grain-of-salt figures.

I may try again on my way home from work. No promises though.

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Offline Bobby Shafto

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Re: The Horizon is Always at Eye Level
« Reply #303 on: May 24, 2018, 01:10:10 AM »
It's not my objective to measure any difference between horizon and eye-level. I only want to know if its possible to ascertain that there is (or isn't) a difference with increases in elevation.

After painstakingly calibrating this theodolite app (which has a thick crosshair and is gradated in 0.1° increments which I can't determine where they increment (midpoint rounding? threshold crossing?), I gave it a try today, sighting on the smaller Middle Coronado Islands, 17.5 miles south of the old lighthouse on Point Loma, from an elevation of about 410' (+/- 10):

Point Loma
H=400ft
estimated (globe earth) visual horizon=129369ft
anticipated angle=89.82°
anticipated "dip"=(00.18°)



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Offline Bobby Shafto

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Re: The Horizon is Always at Eye Level
« Reply #304 on: May 24, 2018, 01:15:29 AM »
And given that the summit of the larger of the 2 islands in the frame is right about 400' also, I tried to sight the cursor on its peak to obtain "eye level"



The app was cycling between 00.0 and -00.1, but simply pushing the button to get the screen cap would push it over whatever threshold it has to roll over to the first increment of negative pitch.

Bottom line is the apparent horizon is not inline with the summit of that island, which it should be if the horizon is at eye level.

Perhaps it's just not clear enough. I doubt it, but maybe the clearer the atmosphere gets, the closer the horizon will rise to that peak.

We'll see.

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Offline Bobby Shafto

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Re: The Horizon is Always at Eye Level
« Reply #305 on: May 24, 2018, 01:16:50 AM »
Same location. Same time. Better camera.

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Offline Bobby Shafto

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Re: The Horizon is Always at Eye Level
« Reply #306 on: May 24, 2018, 01:21:34 AM »
Not taken today, and not by me, and not at the same elevation (aerial shot), but this is the view looking back toward San Diego from those islands. Point Loma is the mound above the horizon, just right of center of the frame:
« Last Edit: May 24, 2018, 02:08:07 AM by Bobby Shafto »

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Offline Bobby Shafto

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Re: The Horizon is Always at Eye Level
« Reply #307 on: May 24, 2018, 02:27:08 PM »
This is the explanation of horizon (H) based on the "natural law of perspective" in Earth not a Globe


This is an elaboration of what Rowbotham is explaining, and how to calculate distance to H on a flat earth surface:


Observer height (eye level) in this picture is 410'. The distant island height is at the same height.
The calculated distance to H from a viewpoint of 410' according to this flat earth calculation is 260 statute miles.
If true, then the clearer the visibility to the horizon, the higher up the elevation of that island the horizon line will appear, until reaching a maximum level with the peak (level with the eye):

Same location. Same time. Better camera.



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Offline Bobby Shafto

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Re: The Horizon is Always at Eye Level
« Reply #308 on: May 24, 2018, 07:48:17 PM »
Now that I've discovered this natural eye-level viewpoint, I'll watch for varying surface visibility conditions and check/photograph that Central Coronados island and see how much the horizon shifts vertically, and if it ever approaches eye-level.

[deleted original graphic; updated and corrected later in this topic and attached below.]

From yesterday (5/23/2018):
« Last Edit: May 27, 2018, 03:26:48 PM by Bobby Shafto »

Max_Almond

Re: The Horizon is Always at Eye Level
« Reply #309 on: May 24, 2018, 09:20:18 PM »
So am I reading this right?



The top line is eye level; the bottom line is where the horizon only appears to be because of haze and perspectives and optics; and the space in between is actually supposed to look like the sea, and it's just coincidence that it looks like the sky?

Is that how Rowbotham had it?

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Offline Bobby Shafto

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Re: The Horizon is Always at Eye Level
« Reply #310 on: May 24, 2018, 11:13:56 PM »


The top line is eye level; the bottom line is where the horizon only appears to be because of haze and perspectives and optics; and the space in between is actually supposed to look like the sea, and it's just coincidence that it looks like the sky?

The top line is estimated to be eye level. I'm going to work out what the potential margin for error is because I'm not absolutely sure what the height of the island is. I'm going off one a single topo chart, and comparing photographs. Wikipedia has got to be wrong since it claims the two islands are close to the same elevation, but obviously they are not, and the topographical chart disagrees as well. But if that larger island isn't 4x the elevation of the "pile of sugar," what is it at least? 2x? Could it be 200-300' and not 400'? Right now, my leveling tools are leaning me toward 400', but I don't want be biased.

The observation point could be 400-420'. There are no benchmarks nearby and I'm just going by what all the literature AND the topo map says for that spot. Plus, I have to figure about +3' since I'm using a low wall to steady my shots on.

But for now, yeah. that larger island summit is likely close to eye-level.

The bottom line is the apparent horizon. Visibility is better today, despite an overcast ceiling of 2500-3000'. That's actually kind of nice because instead of a vast expanse of blue, the backdrop is white with a known height. So that "ceiling" at 2500' won't obscure a horizon from a perspective of 400'. It'll converge with the horizon, but much further away according to EnaG reasoning.



I really don't anticipate the horizon line will climb any further no matter how much clearer the surface visibility becomes, but I can continue to watch and record. It seems close to the same today as it was yesterday, even though the horizon is (subjectively) sharper and the contrast between sea and backdrop is greater.



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Offline MCToon

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Re: The Horizon is Always at Eye Level
« Reply #311 on: May 25, 2018, 01:43:56 PM »
In the thread "Horizon rising to eye level and a foolproof way to measure it." Started by Tontogary, Tom Bishop makes this statement:

Quote
The best method would be to find an obstacle of a known height, set it a distance away, and then set the height of your camera to the height of the top of the obstacle. The camera, object, and horizon should make a straight line. The further the objects are located from each other, the better. The horizon should line up with to top of the object, and there would far fewer surveying errors since everything is set on the ground rather than being dependent on aligning angles in a device of unknown calibration or holding everything in your hands.

See here: https://forum.tfes.org/index.php?topic=9462.msg147849#msg147849

The only detail needed is to verify the viewing height and the top of the island height.

Bobby, you are now using an acceptable method to test with a pass/fail if the horizon is at eye level.  This is great progress.
I love this site, it's a fantastic collection of evidence of a spherical earth:
Flight times
Full moon
Horizon eye level drops
Sinking ship effect

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Offline AATW

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Re: The Horizon is Always at Eye Level
« Reply #312 on: May 25, 2018, 02:04:22 PM »
Bobby, you are now using an acceptable method to test with a pass/fail if the horizon is at eye level.  This is great progress.
Spoiler alert:
When Bobby does produce a photo where his height and the distant peak height are the same and the horizon is clearly below it Tom will
1) Question how Bobby knows that the heights are the same and argue forever that it can't be definitively verified or
2) Claim that the horizon is slightly hazy and thus claim that the "true horizon" is actually at eye level.

And round and round we go...

Tom: "Claiming incredulity is a pretty bad argument. Calling it "insane" or "ridiculous" is not a good argument at all."

TFES Wiki Occam's Razor page, by Tom: "What's the simplest explanation; that NASA has successfully designed and invented never before seen rocket technologies from scratch which can accelerate 100 tons of matter to an escape velocity of 7 miles per second"

Offline model 29

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Re: The Horizon is Always at Eye Level
« Reply #313 on: May 25, 2018, 05:26:30 PM »
I started piecing together a water level out of some scrap stuff.  There's a 1500 foot mountain nearby with a view of a major city 60 miles away that is at sea-level. 

Tom should conduct this experiment so he can show us all how it is done properly since he has so many issues with how it is being done so far.

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Offline Bobby Shafto

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Re: The Horizon is Always at Eye Level
« Reply #314 on: May 27, 2018, 02:28:47 PM »
Calibrating:


After much testing, I've resolved that the margin for error in sighting horizontal level through this device is 1/8" of camera height adjustment, within which I cannot distinguish high or low based on leveling of the pair of horizontal sighting strings.

My planned camera set back had been 36" but that produces a +/- margin for error 17.25 miles away of +/-162', which is nearly half of my observation elevation and that of the Central Coronados island. Even though I'm not trying to take sightings to verify the height of the island's summit, it illustrates the sensitivity Tom was talking about with these kinds of observations.

Moving my camera setback to 60" will make the margin of error more comfortable, especially since I'm not measuring the dip angle but just  assessing -- pass/fail -- if the horizon is at eye-level. This will just add some degree of assurance that the distant island's summit is, in fact, in transit with 400' level of the eye from the observation point.



I think I've done all the prep and planning. Gotten some preliminary photos. Now it's just a matter of watching to see if that horizon line ever moves upward , using those islands as an index (with my "perspective cube" as an aid.

If that island summit is eye level, and the horizon never rises to it, then the test verifies that the claim "the horizon is always at eye level" fails.
If the horizon does move, to within at least half of the island's height (allowing for about 194' margin of error), then the test verifies that the claim "the horizon is always at eye level" passes.
« Last Edit: May 27, 2018, 02:30:30 PM by Bobby Shafto »

Offline Tontogary

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Re: The Horizon is Always at Eye Level
« Reply #315 on: May 27, 2018, 02:47:05 PM »
The larger island is Middle Coronado yes?

Nautical charts show the max height to be 76.5M.

The smaller one to the right shows to be 30.7M high.

They are both below your elevation, therefore the horizon should actually rise above the higher peak..........

Also, if you haven't heard of bronies before, that reflects poorly on your understanding of the world that surrounds you. It's practically impossible not to know about them.

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Offline Bobby Shafto

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Re: The Horizon is Always at Eye Level
« Reply #316 on: May 27, 2018, 03:00:09 PM »
The larger island is Middle Coronado yes?

Nautical charts show the max height to be 76.5M.

The smaller one to the right shows to be 30.7M high.

Is that info available online such that you can provide a link? Or, if not, a reference I can cite?

Wikipedia has them both listed at around 100', which you can tell just from my photos isn't right.
The only available topo chart I have doesn't list summit heights specifically, but gauging just from elevations lines, it suggests Central Coronados (the taller one) may breach 400' whereas Pilón de Azúcar (smaller one) is just 100'.

From aerial photos, and judging by the relative heights at distance (though Pilón de Azúcar is a little closer to Point Loma), I was suspicious that the larger was some height greater than 100' and less than 400'.  76.5m is about 250' which does seem to confirm that, and would not put it in transit with the horizon if the horizon is at eye level from a vantage point of 400-410' feet. So, it should make it easier for the "true horizon" to reach that transit line. That's a lower benchmark, but to make it sporting, I'll confer a "pass" on the test if the horizon reaches even that 250' summit mark.

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Offline Bobby Shafto

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Re: The Horizon is Always at Eye Level
« Reply #317 on: May 27, 2018, 03:05:26 PM »
^ Non-sporting-wise, I'll have to redo the calculations for "dip" angle from level and distances/margins of error, now that I have more confidence the larger island summit is lower than my observation point. I'm not sure I'll be able to find a viewing spot that is close to 250'. There's a road/path that the public is allowed to use the runs down closer to sea level, but I'd need a survey marker of some sort to know where 250' of elevation is along that road. (And I'd probably have to ask park rangers for permission to set up, which I'm rather not-inclined to do because I'd have to explain why.)

Offline Tontogary

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Re: The Horizon is Always at Eye Level
« Reply #318 on: May 27, 2018, 03:18:35 PM »
I got the heights from a nautical chart of the area.

I am not sure if you can get an online edition of the chart, as they normally require a subscription.

The other place you may find it would be the US coast pilot. Again i am not sure if you can access it on line for free.

I can take a photo of the screen showing the chart, and height if you wish?

Also, if you haven't heard of bronies before, that reflects poorly on your understanding of the world that surrounds you. It's practically impossible not to know about them.

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Offline Bobby Shafto

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Re: The Horizon is Always at Eye Level
« Reply #319 on: May 27, 2018, 03:25:16 PM »
I got the heights from a nautical chart of the area.

I am not sure if you can get an online edition of the chart, as they normally require a subscription.

The other place you may find it would be the US coast pilot. Again i am not sure if you can access it on line for free.

I can take a photo of the screen showing the chart, and height if you wish?

Please? We'll call it Fair Use? You can just PM it to me.