
There Are Giant Camera Resolution Test Charts Scattered Across the US - rpledge
http://www.petapixel.com/2013/02/15/there-are-giant-camera-resolution-test-charts-scattered-across-the-us/
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jgrahamc
"Even satellites can utilize the charts. Here’s a chart as seen by the
satellite used for Google Maps"

It's not clear that that is a satellite photograph. Just because it was taken
from above it doesn't mean a satellite did it. Mapping services (such as a
Google's) do a disservice to call all this overhead photography 'satellite'.
It's the sort of looseness that causes people to think cellular telephones
also talk to satellites.

~~~
jonknee
It's not that far off, there is a ton of satellite photography in Google Maps.
It's the other way around, but satellites talk to cell phones and I don't
fault people for not knowing it's one-way.

~~~
dhimes
_but satellites talk to cell phones_

Wait wat? I honestly didn't know this (aside from a cell phone with extra
capabilities, like gps).

I thought all phone communications took place with cell towers (except, of
course, for satellite phones).

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jonknee
GPS is what I was referring to.

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NelsonMinar
The source for this PetaPixel article is the Center for Land Use
Interpretation, a really neat organization.
[http://www.clui.org/newsletter/winter-2013/photo-
calibration...](http://www.clui.org/newsletter/winter-2013/photo-calibration-
targets)

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mgeraci
Here's a google maps link to one of the charts mentioned, on Edwards Airforce
Base:

[https://maps.google.com/maps?q=Edwards+AFB,+East+Kern,+Kern,...](https://maps.google.com/maps?q=Edwards+AFB,+East+Kern,+Kern,+California+93523&hl=en&ll=34.834087,-117.759426&spn=0.004412,0.008256&geocode=FUXbFAIdoWP4-A&hnear=Edwards+AFB,+East+Kern,+Kern,+California+93523&t=h&z=18)

~~~
SoftwareMaven
Fascinating that there are air craft relics near the charts. I can only
imagine that is part of the calibrating: so they can tell how large an
aircraft is and what resolution they get for the size.

~~~
_djo_
Indeed, plus one of the aircraft is one of only two remaining examples of the
X-21 [0]. I suspect the other is also derelict on the range somewhere.

<http://en.wikipedia.org/wiki/Northrop_X-21>

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stevenrace
Is this test pattern in use in other known research?

Most of the test patterns I've encountered in using 'OpenCV' [1], 'laser
scanning'[2], and 'structured light scanning' [3] have used equal sized
geometric shapes. Not increasing in scale, so maybe that's useful.

[1] [http://graphics.stanford.edu/~vaibhav/projects/calib-
cs205/c...](http://graphics.stanford.edu/~vaibhav/projects/calib-
cs205/calibimg.png)

[2] [http://www.david-
laserscanner.com/wiki/_media/user_manual/sc...](http://www.david-
laserscanner.com/wiki/_media/user_manual/screenshot_calib_pattern1_small.jpg)

[http://www.sciencedirect.com/science/article/pii/S0143816607...](http://www.sciencedirect.com/science/article/pii/S0143816607000991)

[3]
[http://opticalengineering.spiedigitallibrary.org/data/Journa...](http://opticalengineering.spiedigitallibrary.org/data/Journals/OPTICE/22111/053604_1_5.png)

~~~
daniel_reetz
It is known as the 1951 USAF Test Chart, and it is and was a standard:

<http://en.wikipedia.org/wiki/1951_USAF_resolution_test_chart>

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stevenrace
Exactly what I was looking for, thanks.

It seems the 'Milspec' status is:

    
    
      MIL-STD-150A, dated 06 January 1998, is hereby cancelled without replacement.
    

With as many multi-spectral instruments we have floating about, I wonder what
other shapes, compositions, or controlled temperature gradients might be in
use under our noses.

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brudgers
Throw away business idea: QR codes for large tract real estate listings.

~~~
stevenrace
The prerequisite being a 'Maps' site with <weekly aerial updates. While
relatively plausible today (a few styrofoam drones, camera arrays, pay fer
acre for 'crowdsourcing', ...)[1], the legal woes are frightening.

[1] 'relatively plausible' in relation to 'cubesats' and other aerospace
driven monitoring.

~~~
brudgers
A lot of real-estate sits for years. Weekly photos aren't really necessary.

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biot
Also, large compasses about 1km in diameter: <http://goo.gl/maps/6wTtb>

~~~
_djo_
Those aren't for the same purpose, they're for test pilots to use when landing
on the lakebed runways that you can see next to the compass.

Both the X-1 and X-15, amongst many other experimental planes, landed on the
lakebed rather than on conventional runways at Edwards AFB.

~~~
sargun
Why did they land on the lake bed as opposed to runways?

~~~
lutusp
Because in experimental craft, one doesn't want to have to line up with a
runway when the controls have stopped functioning or a wing has partly fallen
off.

Once, when a test pilot landed the X-15 on a lakebed, the fuselage broke in
two:

[http://www.air-and-
space.com/x-15%20forty%20years%20later%20...](http://www.air-and-
space.com/x-15%20forty%20years%20later%20200001.htm)

Quote: "The X-15-2 on Rosamond Dry Lake following mission 2-3-9*. The fuselage
failed when the nose gear impacted the ground. The shock absorbing ability of
the front landing gear strut was impaired by foaming of the oil in the strut
when it was extended. The back of the X-15 broke at a structural join behind
the cockpit."

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thomasbk
Idea: remember the EURion constellation?
<http://en.wikipedia.org/wiki/EURion_constellation>

It's a pattern of circles that's printed on money, and when printers detect it
in a file they will refuse to print that file. I wonder what would happen if
we similarly embedded this pattern in landscapes. Would it prevent printing
aereal photo's?

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gonzo
fiducials, not so much for a 2-D 'where', but to help deal with the blurring
(<http://what-if.xkcd.com/32/>)

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bhauer
Any idea why some of them, especially the images from EAB, appear to cast
shadows? That is, the white blocks appear to be bordered by black.

~~~
rdtsc
Sometimes these pictures are taken with 3 separate lenses and filters -- one
for each color. Then they are merged. Sometimes that could get out of
alignment.

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wtracy
Does anyone know of any of these charts at locations accessible to the public?
They appear interesting to look at.

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rikacomet
They could have made it a bit more interesting, by coding a secret short
message into them (yawn).

But nonetheless, a interesting article.

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eCa
> by coding a secret short message into them

Maybe there is a _secret_ message in them...

~~~
moo
DUN-DUN-DUUUUN!!!

~~~
willis77
"Be sure to drink your Ovaltine."

