Longest lines of sight photographed.......

Post general questions and discuss issues related to climbing.
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Dmitry Pruss

 
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by Dmitry Pruss » Mon May 04, 2009 10:06 pm

Chester's calculation isn't very far off as you can see; to do a "real" "exact" calculation, one would have to obtain measurements of temperature / pressure / humidity at all elevations between the camera and the peak being photographed ... so of course the formulas use a series of assumptions and simplifications. Which may or may not be right.

Most notably, if you have temperature inversion conditions, the vertical gradient of air density may become more pronounced, and then your distance of sight may be longer than the models predict?

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Day Hiker

 
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by Day Hiker » Tue May 05, 2009 3:43 pm

MoapaPk wrote:DH- It seems to me that you took clear pictures of the CA Sierra from the shoulder of Stirling NV in 2006. How do those pics match with your synthesize projection? If they match, I doubt you have a significant uncertainty from earth radius in that region.

It seems to me that even though the earth is slightly pear-shaped, the planet is still largely radially symmetric about the spin axis. I don't think an ESE view would give that much uncertainty from your spherical approximation.


Thanks for the reassurance about using a spherical Earth. I still plan to eventually use the ellipsoid model, but I haven't yet incorporated that into my code. When I do, I will make some comparisons, just to see if it makes any visible difference.

I checked my photos from 29 Jan 2006, and I have photos from Stirling, but all the telephoto shots are from Peak 2421m. So I will need to generate images using that viewpoint, instead of the views from Stirling that I already have.

We did have some high clouds that day that reduced the contrast between distant peaks and sky, so it will still be hard to do the comparison. I did get some clear shots of the petroglyphs up there, but I doubt I'll have good luck when I compare those shots with topo simulations.

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Day Hiker

 
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by Day Hiker » Tue May 05, 2009 4:16 pm

miczanin wrote:
Day Hiker wrote:Or maybe the viewfinderpanoramas program tries to use the help of atmospheric refraction. My program ignores any potential help from the atmosphere because I'm not sure how much I can count on that phenomenon.


Yes, in order to be realistic you have to consider atmospheric refraction... its effect is not easy to model, because it depends on many factors, some of them almost impossible to know. So, it is necessary to approximate it. Both our marmota system and viewfinderpanoramas use a simple function of distance. We have an extensive experience of matching synthetic data with real photos and the approx we use is to reduce the effect of earth curvature by multiplying it by 0.859 (empirical magic number!).
In some rare case the refraction effect is stronger and our model is too pessimistic. Viewfinderpanoramas aim is not direct photo matching, but to contemplate also exceptional conditions, so it uses a very optimistic refraction model, that is almost equivalent to using 0.825 instead of 0.859 in our system.

We discussed these differences in our 'longest line of sight' blog entry: http://tev.fbk.eu/marmota/blog/2008/10/21/longest-line-of-sight-an-update/


I'm convinced about the effect of atmospheric refraction. After all, it's what brings up the bottom of the Sun's shape during sunrise and sunset, flattening it into what is definitely non-circular.

In your determination of the empirical value .859, did you establish this using multiple views or the one long, 500 km view from your link?

I also thought about using a factor to reduce the Earth's curvature, but I haven't had a chance to do any work with that yet. And I will need to select some appropriate viewpoints and photos to arrive at an empirical value like you did. I guess I could just steal your number for a starting point, but I would eventually want to confirm it.

For the code, the complicated part for me is that I use the Earth's radius to determine where a point is, in 3-D space, not just how much of Earth's curvature is between it and an observer. Simply increasing the radius for all calculations would not give me proper results. I would need to somehow use this adjustment factor only after I have determined each point's location.

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Day Hiker

 
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by Day Hiker » Tue May 05, 2009 4:31 pm

MoapaPk wrote:
MOCKBA wrote:
The refraction effect is due to the reduction of air density (and hence refraction coefficient) with altitude? Would it be lower at higher elevations (where refraction values at all relative elevations are lower?)


I'd guess so; the differential version of Snell's law can be integrated from a starting azimuth. Since the index of refraction drops with altitude, the ray will be gradually bent down.

How does the index of refraction of air go with density? We can calculate the density with altitude. I will be interesting to see where the theoretical answer (for the total refraction effect) falls in comparison with reality.


Just to complicate things more, I wonder how much of the observed effect is due to the atmosphere and how much is due to gravity. I know that link focuses on more massive objects, like galaxies, but light does "bend" in any gravitational field. (Or light travels in a straight line, and space is bent.)

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MoapaPk

 
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by MoapaPk » Tue May 05, 2009 5:12 pm

That's why some very dense people have poor vision.

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Day Hiker

 
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by Day Hiker » Sat Feb 13, 2010 10:05 am

Here is a simulated view, looking northeast from Bakersfield, CA on a clear day. The angle of view is 90 degress, spanning from north to east. The colors are by elevation only, not actual Earth colors.

Image

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Grampahawk

 
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by Grampahawk » Sat Feb 13, 2010 7:10 pm

I don't know how far away they are from each other but we got a lot of summit photos in Mexico. You can see Popo ,Izta and others from Pic de Orizaba.

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Gafoto

 
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by Gafoto » Sun Feb 14, 2010 6:55 am

This seems like the thread to ask for some ID work. Last year I hiked Mount Peale above Moab, Utah in mid October, just after some early season snow had hit Colorado. I could see some gorgeous snow-capped peaks in Colorado and this first picture faces east and slightly south. I'm almost sure it's the San Juans. In the foreground is route 90 heading towards Telluride.

Click for the full size image:
Image
I'd love to know what that extremely distinctive peak to the far south is.

This second picture I'm not so sure about. This is facing just slightly more northern than the previous shot, looking roughly in the direction of Aspen. These mountains were really far away and I still have no idea exactly which ones these are.

Click for the full size image:
Image

Any Colorado natives able to ID these mountains? Sorry for the poor picture quality, I had to try to increase the visibility with some photo editing.

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billisfree

 
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Not Rainier

by billisfree » Sun Feb 14, 2010 8:28 am

The sunset picture presented in the first post strongly appears to be Mt. Adams to me.



Image

It's kinda hard to get a really sharp detailed topo pictures... because I need
to back off quite a distance, to make sure the provile is not deformed
by rendering the pictures too close.

Mt Adams has 3 "humps" while Rainier has two.

Plus a few other obvious features.

Remember light bends in the air and can sometimes create mirages... making
a mountain look taller than normal.

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Day Hiker

 
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by Day Hiker » Sun Feb 14, 2010 7:26 pm

Gafoto wrote:This seems like the thread to ask for some ID work. Last year I hiked Mount Peale above Moab, Utah in mid October, just after some early season snow had hit Colorado. I could see some gorgeous snow-capped peaks in Colorado and this first picture faces east and slightly south. I'm almost sure it's the San Juans. In the foreground is route 90 heading towards Telluride.

Click for the full size image:
Image
I'd love to know what that extremely distinctive peak to the far south is.


That's Lone Cone on the right. I will have more later.

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seano

 
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I can see Colorado from here!

by seano » Sun Feb 14, 2010 10:36 pm

San Antonio Mountain from Santa Fe Baldy:
Image
Either Culebra or Blanca (I think) from Santa Fe Baldy (giant original here):
Image

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Day Hiker

 
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by Day Hiker » Sun Feb 14, 2010 11:03 pm

Here is the labeled (and resized) photo, with the computer-generated image from my program below for comparison.

Image

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Gafoto

 
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by Gafoto » Mon Feb 15, 2010 1:16 am

Whoa, that is really cool. Seeing over 100 miles is very impressive for a east coaster like me.

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Day Hiker

 
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by Day Hiker » Mon Feb 15, 2010 2:15 am

Gafoto wrote:This second picture I'm not so sure about. This is facing just slightly more northern than the previous shot, looking roughly in the direction of Aspen. These mountains were really far away and I still have no idea exactly which ones these are.

Click for the full size image:
Image

Any Colorado natives able to ID these mountains? Sorry for the poor picture quality, I had to try to increase the visibility with some photo editing.


I generated an image to compare, but the link for the full-size photo is asking for a yahoo login. Do you have another way for me to see it? The other photo worked without this problem.

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Alpinist

 
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by Alpinist » Mon Feb 15, 2010 2:29 pm

And the winner is......!

Light from a star that exploded 13 billion years ago has been detected, becoming the most distant object in the universe ever observed.

The light from the distant explosion, called a gamma-ray burst, first reached Earth on April 23, 2009 and was detected by NASA’s Swift satellite. Gamma-ray bursts are thought to be associated with the formation of star-sized black holes as massive stars collapse.

Two teams, one using the European Southern Observatory’s 8.2-meter Very Large Telescope, located in La Silla, Chile, and the other using the 3.6-meter Italian Telescopio Nazionale Galileo in Spain, pinpointed the distance to the blast, dubbed GRB 090423, at more than 13 billion light-years from Earth. (The previous record holder, GRB 080913, was 12.8 billion light-years distant.)



Source.

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