- #1
kent davidge
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I saw the following question in Yahoo Answers,
Is it even possible to know this?
Is it even possible to know this?
Can Height, Shadow Length, and a Photo Reveal a Person's Location?
- Context: High School
- Thread starter kent davidge
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Discussion Overview
The discussion revolves around the feasibility of determining a person's location on Earth using their height, the length of their shadow, and a photograph taken at a specific time and date. The scope includes theoretical considerations and practical implications of navigation based on these parameters.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
Main Points Raised
- Some participants suggest that knowing the time in UTC could allow for determining a location.
- Others question the accuracy of such a determination, raising concerns about error bars and the necessity of orientation information (e.g., which way is North).
- It is noted that without orientation information, there could be a wide range of possible longitude and latitude solutions, potentially mirrored in both hemispheres.
- One participant mentions that the same stick length will yield the same shadow length at multiple locations globally, complicating the determination of a specific location without additional information.
- There is a discussion about the importance of knowing the azimuth of the sun and how it relates to determining longitude and latitude.
- Another point raised is that if the ground is not level, navigation could be significantly affected.
- A humorous reference is made to a photo context involving penguins, suggesting that contextual clues in the photograph could aid in location determination.
Areas of Agreement / Disagreement
Participants express multiple competing views regarding the feasibility and accuracy of determining a person's location based on the given parameters. The discussion remains unresolved with no consensus reached.
Contextual Notes
Limitations include the dependence on orientation information, the potential for multiple solutions based on shadow length, and the impact of ground level on navigation accuracy.
- #2
russ_watters
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If you have the time in UTC, sure.
- #3
DrClaude
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But with what error bars?russ_watters said:
If you have no orientation information (which way is North?), then there is quite a wide band of longitude+latitude solutions, mirrored on each hemisphere.
- #4
russ_watters
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Accurate enough to navigate a ship in the 19th century...DrClaude said:
Good point; you would have to know the hemisphere, which maybe you could see from context in the photo.
- #5
DrClaude
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Not without a compassruss_watters said:
My point is that at any given time, the same stick length will give the same shadow length at many points on the globe. If you have no information on the orientation of the shadow, there is not much you can say.
- #6
russ_watters
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Oh, you don't just mean the hemisphere. Yes, I see you're right; to get the longitude from the azimuth of the sun, you need the actual angle from north.DrClaude said:Not without a compass
and...now that I think about it, without longitude (and with it local time) first, the altitude doesn't tell you latitude either.
- #7
jbriggs444
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The azimuth just positions you somewhere on a circle that is centered on a point where the sun is directly overhead. A compass heading could position you on that circle.
Edit: if the ground is not level, your navigation could be way off.
Edit: if the ground is not level, your navigation could be way off.
- #8
sophiecentaur
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The one with the penguins in, perhaps.russ_watters said: