# San Mateo Bridge to Bay Bridge 17 mile curvature test

#### sirtwentythree

##### Member
Last edited by a moderator:

#### Trailblazer

##### Moderator
Staff member
Also if you look at the last image you can see that there is a lot of looming which suggests that refraction is higher than normal. Look especially at the right end of the bridge here.

#### Henk001

##### Senior Member.
Also if you look at the last image you can see that there is a lot of looming which suggests that refraction is higher than normal. Look especially at the right end of the bridge here.
Agree. There is about 47 ft hidden. The question should be: How is that possible on a flat Earth?

#### Mick West

Staff member
Yes, notice the mirage reflection of the headland on the left:

Compare it with what you would get on a Flat Earth. The following view of the bridge is taken from the same spot, but 150 feet in the air. The view of the bridge is essentially unchanged as the angle hardly changes. However you can now see all of it, and hence see the effects of refraction, and where the bottom of the bridge actually is relative to the horizon.

Drag slider to compare

Last edited:

#### sirtwentythree

##### Member
With all the numbers I've read here. I'm still seeing that under no circumstances whatsoever should we still be able to see 90-95% of a 220ft gap at 17 miles away.

#### Mick West

Staff member
With all the numbers I've read here. I'm still seeing that under no circumstances whatsoever should we still be able to see 90-95% of a 220ft gap at 17 miles away.

You can't, and you don't. Look at my post above. The first image shows a red line where you can start to actually see the land and bridge. Below that is a reflection (notice the hill in the circle).

The second image is an interactive comparison. Drag the slider to see how much is obscured (of the bridge, ignore the hills for now).

#### sirtwentythree

##### Member
What is what's below the red line reflecting off of?

#### Mick West

Staff member
What is what's below the red line reflecting off of?
The air. It's a total internal reflection, like a mirage on a hot road.

#### sirtwentythree

##### Member
So one would have to be able to zoom in far enough to prove they are actually seeing further down the base of one of those columns for this to have any merit? That can easily be tried.

#### deirdre

##### Senior Member.
So one would have to be able to zoom in far enough to prove they are actually seeing further down the base of one of those columns for this to have any merit? That can easily be tried.
columns are tough because they generally look the same all the way down. These columns are on a pedestal of sorts but it think FEers would just explain not seeing it as 'waves blocking the view'. A big boat traveling under the bridge would help more.

Last edited:

#### Mick West

Staff member
So one would have to be able to zoom in far enough to prove they are actually seeing further down the base of one of those columns for this to have any merit? That can easily be tried.

Really they need to try try it at different times of day, preferably when it's cool. The problem is the heat mirage is obscuring the actual physical horizon.

#### Henk001

##### Senior Member.
columns are tough because they generally look the same all the way down. These columns are on a pedestal of sorts but it think FEers would just explain not seeing it as 'waves blocking the view'. A big boat traveling under the bridge would help more.
A bit like this picture I took a few years ago. There are several reflections with different ships (roughly indicated by the added lines) yet the columns appear to be unaffected.

#### Henk001

##### Senior Member.
A bit like this picture I took a few years ago. There are several reflections with different ships (roughly indicated by the added lines) yet the columns appear to be unaffected.
But it really is affected. In the next picture I pasted the same column (but now complete from a different standpoint) and you can see that the lower part of the column is reflected so it appears to be longer than it actually is.

#### Whitebeard

##### Senior Member.
columns are tough because they generally look the same all the way down. These columns are on a pedestal of sorts but it think FEers would just explain not seeing it as 'waves blocking the view'. A big boat traveling under the bridge would help more.

And finding out exactly when a vessel is passing under the bridge, and detail of the vessel are easy to find
https://www.vesselfinder.com/?lat=37.82376&lon=-122.45464&zoom=12

#### sirtwentythree

##### Member
columns are tough because they generally look the same all the way down. These columns are on a pedestal of sorts but it think FEers would just explain not seeing it as 'waves blocking the view'. A big boat traveling under the bridge would help more.

I understand that it might be difficult if the column was completely vertically symmetrical. A very simple way around columns being "tough" is to just put markers on them going down, unique markers to do away with any symmetry, correct?

#### Mick West

Staff member
I understand that it might be difficult if the column was completely vertically symmetrical. A very simple way around columns being "tough" is to just put markers on them going down, unique markers to do away with any symmetry, correct?

I'm pretty sure the bridge authorities would have a problem with you doing that

You can see there's major mirages going on without that, just look at the hillside on the left.

#### sirtwentythree

##### Member
Really they need to try try it at different times of day, preferably when it's cool. The problem is the heat mirage is obscuring the actual physical horizon.

To me the problem appears more to be it's not zoomed in far enough to prove that it's a mirage or not. I understand how a mirage is perceived, but if one could take a telescope and see very close to the base of one of those columns, I think the time of day would be irrelevant, given there's enough light.

#### Crackton

##### New Member
This guy did it with a tower in Malmoe that has clear markings

#### deirdre

##### Senior Member.
To me the problem appears more to be it's not zoomed in far enough to prove that it's a mirage or not.
concentrate on the mountain, not the coloumns. the sky is visible under the mountain which is impossible unless its a mirage.

#### sirtwentythree

##### Member
I do see that, but there's nothing to tell me that that is truly a reflection. We just gotta zoom in more to figure this one out.

#### deirdre

##### Senior Member.
I think the time of day would be irrelevant, given there's enough light.
it's cooler in the mornings. heat hasn't built up. I think Mick is saying that if you take pics in morning and then midday (if its hot) you can see for yourself the difference in refractions/reflections.

#### sirtwentythree

##### Member
This guy did it with a tower in Malmoe that has clear markings

He's failed to take into account the height of the camera lens, right?

#### sirtwentythree

##### Member
it's cooler in the mornings. heat hasn't built up. I think Mick is saying that if you take pics in morning and then midday (if its hot) you can see for yourself the difference in refractions/reflections.
I got it. More or less refraction depending on the temperature. This is not taking into account that we're still not zoomed in close enough to truly tell though, right?

#### deirdre

##### Senior Member.
I do see that, but there's nothing to tell me that that is truly a reflection. We just gotta zoom in more to figure this one out.
hhmm. its a mountain.

add: (above pic) mountain that bottoms full length into the bay

versus: mountain that doesn't.

Last edited:

#### sirtwentythree

##### Member
This guy did it with a tower in Malmoe that has clear markings

The tip of the tower doesn't appear to be angling back as it should the further and further we view it from.

#### deirdre

##### Senior Member.
The tip of the tower doesn't appear to be angling back as it should the further and further we view it from.
lets not go off topic. the alleged 'lean back' has been discussed in other threads.

Last edited:

#### Crackton

##### New Member
He's failed to take into account the height of the camera lens, right?
The heights are in the description. 1.5m and also 16m at the last one

#### Z.W. Wolf

##### Senior Member.
You should be clear what an inferior mirage is.

Everyone has seen inferior mirages on the road. What is the light "reflecting" off of? The answer: it's not reflecting. The light is refracting. The road surface is hot. There's a layer of hot air just above the road. Hot air is less dense than cold air. Dense air has a different refractive index. The light gets bent in a surprising way, just the way water or glass will bend it. The water on the road is a refracted image of the sky above.

Multiple inferior mirages of the same bus. The road is slightly uneven. The angle is just right in several different places for the light from the bus to get refracted (not reflected!) to the camera.

"Floating islands": Inferior mirage makes it appear that the island is floating. It's just an inferior mirage. The "sky" beneath the island is a refracted (not reflected) image of the sky above the island. As pointed out, if you look at the photo of the bridge you can see a mountain on the left with sky underneath its horizontal point. That wouldn't change if you had a stronger lens. You'd just see the same thing more clearly.

Last edited by a moderator:

#### Z.W. Wolf

##### Senior Member.
The heights are in the description. 1.5m and also 16m at the last one

But he's not taking it into account in his calculations. His calculations assume the camera is at ZERO FEET above the water.

Last edited:

#### Z.W. Wolf

##### Senior Member.

Here's a good inferior mirage photo taken from another thread right here in this MB. What is it?

It's this. Not at the same moment and not the same angle, but you can see the same table.

Explanation: This was taken through a powerful telephoto lens from a boat on Lake Balaton in Hungary. It's an inferior mirage of people standing on the breakwater.

The colored lines label the original and the inverted image. The blue lines label a man in a red shirt and his inverted image; the red lines label a man in a white shirt and his inverted image, and so on. These inverted images are not reflections in the water.

It's tempting to see this as a boat with an outboard motor (green line); but that "outboard motor" is just an inverted image of a white sign or something similar.

The table gives you a good reference point to see the separation point between the normal image and the inverted image of the mirage.

(For those members here in the know, the guy in red is Sandor.)

Last edited:

#### Crackton

##### New Member
But he's not taking it into account in his calculations. His calculations assume the camera is at ZERO FEET above the water.
What calculations? There isn't any calculations needed, only location and distance.

The visual effect of the tower being behind the horizon is so obvious, you don't need to calculate anything. But if you think it's bogus, why don't you show exactly where he's wrong? Show the calculations and the error and explain what it means to what we see

Edit: also, observer height is in his calculations https://flic.kr/p/EseKVJ

#### Ray Von Geezer

##### Senior Member.
What calculations? There isn't any calculations needed, only location and distance.

The visual effect of the tower being behind the horizon is so obvious, you don't need to calculate anything. But if you think it's bogus, why don't you show exactly where he's wrong? Show the calculations and the error and explain what it means to what we see

Edit: also, observer height is in his calculations https://flic.kr/p/EseKVJ

But he's not taking it into account in his calculations. His calculations assume the camera is at ZERO FEET above the water.

I think you two are talking at crossed purposes- mixing up the tower and the bridge?

Ray Von

#### Marin B

##### Active Member
Another variable is the changing tide - the water line can vary about 7-8 feet/day.

#### Whitebeard

##### Senior Member.
Another variable is the changing tide - the water line can vary about 7-8 feet/day.
This is important to take into account. 7-8 feet is a global average. Some places have very sallow tides, eg The Black Sea, where the tidal range can be as little as 1-2 feet, or the Seven estuary / Bristol Channel in the UK where the tidal range can up to 50 feet
https://en.wikipedia.org/wiki/Severn_Estuary

#### DougK

##### New Member
I did the same pics from the San Mateo bridge from the exact spot 1 meter above the water.
Saw lots of curvature.

Last edited by a moderator:

Replies
42
Views
3K
Replies
2
Views
533
Related Articles