View Full Version : how far do you?
GuyedGuy
Sep 26, 2003, 12:04 PM
How far would you have to be away from a building to take a photo at the same scale as the diagrams?
can anyone calculate that?
Kelvin
Sep 26, 2003, 1:06 PM
There is no particular solution top that question.
In addition to your physical distance from the object, you would need to consider lens type, zoom factor, and your final print size.
Your best bet is to use photo-editing software to adjust your image to your intended scale.
Tony
Sep 26, 2003, 1:19 PM
Come on Kelvin! I expected more of an answer from you than that! Do the math Mr. Engineer. :P :)
Assume, standard 35mm camera zoomed at let's say 38mm focal length.
Kelvin
Sep 26, 2003, 2:10 PM
Well if that's the case, then stand at a distance sufficient to capture the full height of the structure within the view window and take your shot. Standing as far back as you can with max zoom offers the least amount of perspective distortion.
Then either download or scan the image and manipulate with your fav photoediting software
GuyedGuy
Sep 26, 2003, 8:38 PM
well, i was wondering so I could upload an image to the photoediting software then find its height lol
Dylan Leblanc
Sep 27, 2003, 1:16 AM
I don't think you could do it that way. But you might want to look into something called paralax. By knowing the distance you are from an object, and the angle you are view it at, you could calculate the height of it (basic geometry). But I doubt any of us could really do this accuratly.
Kelvin
Sep 27, 2003, 2:49 AM
There are surveying instruments that have special cross-hairs on them that can be used for what Dylan describes and back in the bad-old-days we used them for doing things like measuring distance and elevation to objects (if you took a whole bunch of shots using this type of equipment at various ground points you can derive a contour map - also called a stadia survey).
Today a single (very expensive) instrument does the job and uses infrared sights and reflective targets. They are tremendeously accurate ( I would wager you could measure a skyscraper to the millimeter), but like I said: $$$$$!
GuyedGuy
Sep 27, 2003, 2:59 AM
isn't it called... err i can't remember it
they fly a plane over the target area, then it maps the elevation and can show the heat. They use it on 9/11 for a map and reference for firefighters and volunteers for recovery.
EDIT:
This is what i am talking about:
http://www.noaanews.noaa.gov/stories/images/wtc2b.jpg
Kelvin
Sep 27, 2003, 3:04 AM
You are thinking of infrared thermal images, but these instruments are the little orange or green gizmos that you see on tripods.
http://www.davidwebbsurveys.com/images/Instrument.jpg
You can also do stadia surveys using airplane photogrametry methods and other means, but these methods are generally even more expensive!
bgwah
Sep 27, 2003, 3:05 AM
I wish there was a simple way to find out how tall a building is!
GuyedGuy
Sep 27, 2003, 3:06 AM
airplane photogrametry methods
is that like aerial photos like my avatar?
i wish there were too ;)
Kelvin
Sep 27, 2003, 3:11 AM
Similar yes. Photogrametry uses a series of photos taken at regular intervals from an airplane flying a constant altitude. When all the photos arte assembled in correct order, they can be put in a special viewing device that only lets your left eye see one photo and your right eye the other. When you get them properly set, it becomes a 3D image so real you think you were looking at the ground from the belly of the plane. There are then special mechanical devices that allow you to determine relative distance to the ground at different points.
GuyedGuy
Sep 27, 2003, 3:15 AM
could this "special device" be homemade? (i doubt it, but i had to ask)
It kinda stinks, cause now im contacting City Hall, the KC Public Library, and the Building Codes people requesting building info, as the people who own the buildings won't tell me a thing.
Also, do you know how to read a topographical map??
Kelvin
Sep 27, 2003, 3:43 AM
Serge devised a simple homemade instrument that he said was pretty accurate. I have every reason to believe that it would be and all you need is a:
- a simple carpenters level with a 45-bubble
- a camera/video tripod
- a wheel-o-meter-thingy
I think he said he put his together for under $100. That's a far cry from the $500 you would need for a transit, $5000 for a theodolite, or $50,000 for a total station!
GuyedGuy
Sep 28, 2003, 1:21 AM
Kelvin, are we able to find the heights of these power plant stacks?
One is Sibley, MO and the other is Iatan, MO
According to the source they are 1 pixel = 1 meter
Iatan has a known height, sibley does not
http://www.kcskyscrapers.com/albums/kcguyedguy/sibleyiatanaerial.jpg
Kelvin
Sep 28, 2003, 3:40 AM
I don't see how you can get anything from those photos. A shadow projected along the ground means nothing unless you know the stack's height, the time of day, time of year and position on the globe. I find it hard to believe that someone calibrated their photographic equipment that exactly that they could say it's precisely 1m to the pixel.
It's possibly part of an aerial survey, but the heights of neither of those stack's is determinate from that info. Sorry :(
Did you try emailing those power companies that operate them?
GuyedGuy
Sep 28, 2003, 3:42 AM
yup, they couldn't tell me the info due to "recent release of information" and that "due to security we cannot release this information" so...
However I can see Sibley from my home
Kelvin
Sep 28, 2003, 3:56 AM
Security??? What secrets are they protecting I wonder?
GuyedGuy
Sep 28, 2003, 3:57 AM
dunno, i asked the width of the chimney at the base and top then the height... nothing
Kelvin
Sep 28, 2003, 4:07 AM
I wonder if the EPA would have anything on file? If there are flight lines near by, the heights would have to be listed as part of the local navigational data too.
GuyedGuy
Sep 28, 2003, 4:08 AM
well the FCC doesnt have it, and im not sure about any airports... hmm, oh and who is the EPA
Kelvin
Sep 28, 2003, 2:06 PM
The Environmental Protection Agency. The are the ones who would permit the stack to operate, monitor it's output, etc.
If there is a flying club operating at your local airport, you could ask them about these stacks and if they appear on any of their flight charts.
GuyedGuy
Sep 28, 2003, 2:38 PM
good idea, but our local airport is for small private planes...
Also, yesterday me and my mother were getting ready to head to get gas, then all the sudden one of the planes flew past our hill at like 300-400mph and was so low it was only about 300-500ft above the ground. Yet we have a 190ft tower near the airport along with several highrises downtown. Could you figure out why it was so low?
GuyedGuy
Sep 28, 2003, 2:45 PM
here are some websites text i found:
These decisions and petitions
for review concern a request submitted by UCU for approval of a method
for apportionment of the nitrogen oxide (NOX) emissions from
a common stack at UCU's Sibley, Missouri facility.
Acid Rain Division, dated October 15,
1999, disapproving UCU's petition for approval of a method for
apportionment of (NOX emissions from a common stack at UCU's
facility located at Sibley, Missouri.
and then nothing else... :(
Kelvin
Sep 29, 2003, 12:08 AM
...Could you figure out why it was so low?
Always hard to say, but as long as he had permission from the control tower for those types of maneouvers it's OK. If he didn't, then he may face losing his licence.
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