Sun Position Question

[oldrover]

Hi, I need to try and understand whether the angle of shadows in two series of photos can shed any light on roughly what time of day they were captured. I have the date and location where they were taken and I've looked at the sun position calculator, but unfortunately it doesn't make too much sense to me. I don't know the camera or lens type, but I do have copies of the negatives of one series. I can't post the pictures publicly as some of them are in a private collection and access is limited. I won't waffle on any further, but if there is someone here who has experience of this and would be willing to help via PM it'd be a great help. Thanks for reading.

 

[Trevp666]

"Red sky at night, shepherds delight....Black sky in the morning, still night...go back to bed!"

I think you'll find that the closer to the equator you are then the shorter the shadows will be, and at noon with the sun directly overhead there is basically no shadow other than that directly beneath the object.
Having the date and location helps, and also if you know which direction the camera was pointing at the time.
More modern pictures, if captured on a suitable device, could possibly have a time stamp in the file info.
If you can download full pictures onto your PC then you can do a 'reverse image search' on Google Image and it will show you matching (or similar) pictures which could be useful.

 

[EnolaGaia]

Taking time of day to be the unknown variable ...

Shadow length can vary depending on latitude and season. You'd therefore need to pin down the geographic location at which the photo was taken as well as the date.

More importantly, you'll need to pin down the direction (north, south, etc.) toward which the camera was pointing when the photo was taken.

 

[Tunn11]

Don't forget that any sloping of the ground will affect the length and possibly angle of the shadow as well. Just look at all the comments about shadow length in the "were the Moon landings faked" debate!

 

[oldrover]

Thanks both. I can't quite get my head around this, but somebody has just contacted me and explained what the crux of the problem is. And is does as EnolGaia said, knowing which way the camera, and the subject was facing. Unfortunately all immediate points of reference were destroyed by fire in 1931. So, looks like I'm stuffed.

 

[EnolaGaia]

Hi, I need to try and understand whether the angle of shadows in two series of photos ...

Your mention of "series" suggests there are multiple photos. Were the photos taken at different times during the same day? If so, there might be a chance of determining a (very) approximate direction in which the camera was pointing. This would depend on how similar the photos are and how much time had elapsed between / among their being taken.

 

[oldrover]

Your mention of "series" suggests there are multiple photos. Were the photos taken at different times during the same day? If so, there might be a chance of determining a (very) approximate direction in which the camera was pointing. This would depend on how similar the photos are and how much time had elapsed between / among their being taken.

There are two series, one with two images probably taken on the 13th. Another definitely taken on the 14th, two in one location, four in another. Both series would have been taken in a fairly short time. Trouble is all the landmarks have gone. The buildings have all gone and there aren't any particularly distinctive features in the background. Personally, I'm pretty convinced that at least some are taken south-north because of the way the fences are running.

 

[EnolaGaia]

Is there any chance there might be some sort of historical documentation of the buildings' / landmarks' locations and orientations? Map? Scene layout diagram? Other photo(s)?

 

[oldrover]

Is there any chance there might be some sort of historical documentation of the buildings' / landmarks' locations and orientations? Map? Scene layout diagram? Other photo(s)?

I have them all, and there's nothing to say where the buildings are in the relevant lot. But, I do see what I'm fairly certain is a building in the distance. There are only two places where this could be, west or north.

 

[charliebrown]

The is sun position varies slightly.

The earth wobbles, but the biggest variation is the 1/4 day for Leap Year built into the calendar which makes things not precise.

 

[Trevp666]

Fences in the pics will usually denote a boundary of some sort - even since 1931 the actual line of any boundary should still be in effect, assuming that the area hasn't been heavily developed at any point since.
If you were able to recreate the fences at the actual location (or nearby) then that would give you the tools to work out the time of day of the original pics.

 

[maximus otter]

Hi, I need to try and understand whether the angle of shadows in two series of photos can shed any light on roughly what time of day they were captured. I have the date and location where they were taken and I've looked at the sun position calculator, but unfortunately it doesn't make too much sense to me. I don't know the camera or lens type, but I do have copies of the negatives of one series. I can't post the pictures publicly as some of them are in a private collection and access is limited. I won't waffle on any further, but if there is someone here who has experience of this and would be willing to help via PM it'd be a great help. Thanks for reading.

Planetcalc will give you the Sun’s elevation and azimuth for any date and location in the last century.

maximus otter

 

[oldrover]

Again, thanks both.

Fences in the pics will usually denote a boundary of some sort - even since 1931 the actual line of any boundary should still be in effect, assuming that the area hasn't been heavily developed at any point since.
If you were able to recreate the fences at the actual location (or nearby) then that would give you the tools to work out the time of day of the original pics.

Unfortunately in this instance the boundaries have changed a lot. But I agree, fences are a potential clue.

 

[Mikefule]

The angle of the sun relative to the horizon at any given time varies from day to day.

The direction of the sun (east/west) changes throughout the day.

Both of the above vary according to where you are on the globe.

The apparent position of the sun at any given moment may be affected by atmospheric conditions, especially when it is low in the sky. For example, when you see the sun set, it is already behind the Earth, but refraction makes it visible.

The length of shadows relative to the height of an object can be considerably affected by even a slight slope in the ground.

I suspect that for this technique to be reliable, you would need to visit the location to check the topography. It might be easier to check an alleged date and time for accuracy then to work out an accurate date and time from scratch.

I feel that, at best, it could only be indicative rather than definitive.

 

[Trevp666]

If it's of any use - 'Bing Maps' allows you to switch between standard mapping and 'ordnance survey' so you can see the contour lines and, as such, infer any incline.
https://www.bing.com/maps/?cp=51.867232~-0.54172&lvl=15.0&style=s

 

[ChasFink]

More importantly, you'll need to pin down the direction (north, south, etc.) toward which the camera was pointing when the photo was taken.

I would think the direction of the camera wouldn't matter if you had an exact date, a precise location, and known level ground. You could extrapolate the length of shadows on objects of known height to get the time of day - or at least the number of hours on either side of noon.

However, if you had an exact date, a precise latitude, and the direction of the camera, you would essentially have a sundial; the direction of the shadows, not the length, would give you a time.

 

[EnolaGaia]

... However, if you had an exact date, a precise latitude, and the direction of the camera, you would essentially have a sundial; the direction of the shadows, not the length, would give you a time.

That's the point. Oldrover is trying to determine the time of day. Number of hours' offset from zenith (noon-ish) doesn't pinpoint time of day.

NOTE: Oldrover and I are separately discussing this via private emails.

 

[Trevp666]

Would there be likely to be any other pictures taken at the same time and place that you could also look at? If so then they might carry some extra info.

 

[EnolaGaia]

Would there be likely to be any other pictures taken at the same time and place that you could also look at? If so then they might carry some extra info.

Oldrover has allowed me to see the photos he has - subject to strict confidentiality (as he mentioned). Don't ask me to share them.

The set of 8 photos were supposedly taken on two consecutive days (2 the day of the killing and 6 the following day) at a single site. The photos basically sort themselves into 3 subsets (1 for the day of the killing and 2 for the following day).

Each subset seems to have been photographed at different specific locations around the site. There don't seem to be any common objects or landmarks visible in the photos that allow correlation among the 3 subsets.

To further confuse the situation, there doesn't seem to be any documentation about the layout of the site (a farm). Without that we have no basis for correlating the photos with exact locations within the site.

Four of the photos taken on the second day seem to show an overcast sky, so there's little that can be evaluated about the shadows.

I think we've determined which way the thylacine corpse is facing (as posed) in the 2 photos from the day of the killing.

Much of our discussion so far has focused on rigor mortis, whether it can explain differences in how the corpse was posed in the various photos, and whether the apparent degree of rigor offers any clues about the time a given photo might have been taken. Long story short - it's anybody's guess regarding the rigor. There's little hard data on the course of animal rigor, it varies among species (and with other variables), and none of the very scarce data necessarily applies to a thylacine.