*Insert standard sorry-if-this-has-already-been-posted disclaimer here*
There is a vast resource of multispectral imagery data available online that includes imagery as recent as last week. NASA's Earth Observing-1 (EO-1)
spacecraft launched on 21 November 2000 and has been providing high-resolution multispectral imagery of the Earth's surface since then. Of particular
interest are certain swaths that the spacecraft images on a regular basis that include Papoose Lake and portions of Area 51 at a decent resolution.
There are two important multispectral imaging instruments on the spacecraft, the Hyperion and the Ali.
The Hyperion is a high resolution hyperspectral imager. It regularly images Papoose Lake and portions of Area 51. The imagery data available online
that it captures each time is a 242-band, 16-bit-per-sample dataset at a spatial resolution of 30 meters. Each of these "snapshots" covers an area
of 4.7 miles (7.5 km) by 62 miles (100 km).
So what's so great about this data? It's not that it's at a fantastic resolution. It's only 30 meters-per-pixel, so you won't be reading any
license plates in the parking lot, but it's good enough that you can distinguish all of the major buildings/features at Area 51. What's great about
this data is that it isn't just your standard 8-bit-per-channel Red-Green-Blue lossy-compressed jpeg image. It is a monstrous set of raw,
uncompressed HDR data spanning a nice slice of the electromagnetic spectrum. Each time Hyperion images Papoose Lake, it records 16-bit data for 242
different wavelength bands from 355.59 nm to 2577.08 nm. By comparison, visible light is only from about 390 nm to about 750 nm, so the imagery dips a
little into the ultraviolet spectrum and dives into the infrared spectrum, covering Near Infrared (NIR) and most of Short-Wavelength Infrared (SWIR).
The resulting dataset is robust enough to do a detailed chemical analysis of the surface. In other words, you can identify not only the color of the
surface/structures/etc in the imagery, but also what
it is, its chemical composition. So, you could positively distinguish different types of
pavement, different metals, different fabrics, different minerals in the soil, etc. For example, Google Earth's current imagery (from 16 November
2006) shows some foam or something all over the taxiway to Hangar 18 and there has been a good bit of debate on the Internet as to whether it were
AFFF or something else. Well if you had Hyperion imagery from that day, you could answer that question definitively.
Before I get carried away writing about how awesome the data is, let's get down to something you might care about. Let's say, hypothetically, that
there are hangar doors in the mountainside next to Papoose Lake disguised with a coating that resembled the rest of the mountainside. Well, even if
you put some artificial coating on those doors that looks
like the natural mountain dirt, its chemical composition, captured by Hyperion, is
still going to be different from the surrounding mountainside, so if it were as simple as that, then there should be a couple pixels in that imagery
that don't match the rest of the mountain.
Now, I'm not too worried about that, because even if there were hangar doors hidden there, they would just use the actual material of the mountain
rather than an artificial lookalike coating, or use some other means to hide it. I'm interested in all the other invisible
stuff. There are a
looooot of things that are the same color
as other things, but they all have their own spectrum. This imagery would show you areas where
chemicals have been dumped, areas where artificial camouflaged structures may be hidden, artificial earthworks, soil brought in from other areas (with
different chemical compositions), and even some areas that are generating their own heat (even subsurface) because blackbody radiation is significant
above about 900 nm.
So how much data is really in one of these "snapshots"? Well a single pixel of a normal uncompressed 24-bit bitmap image has 1.7x10^7 different
possible values. A single pixel of a Hyperion "snapshot" has 3.9x10^1165 different possible values (numbers that high don't have names, by the
way). In normal RGB images, there are 8 bits of data per channel for each pixel, so there are 256 different possible valus for how much red is there,
256 possible green values, and 256 possible blue values. Well, instead of 3 channels, the Hyperion data has 242 channels, and instead of 256 possible
values per channel, there are 65536 possible values per channel. If I haven't yet communicated effectively the precision of this data, I never
Anyway, another instrument on the EO-1 spacecraft is Ali, the Advanced Land Imager. It also regularly records high-resolution multispectral imagery of
Papoose Lake and some of Area 51. The Ali data includes 9 separate 16-bit wavelength bands (in the same general range as Hyperion) at
30-meter-per-pixel resolution in addition to a single 16-bit monochromatic band at 10-meter-per-pixel resolution. The latter is great because it
provides regular, up-to-date HDR (albeit monochromatic) imagery of Area 51 and Papoose Lake. In fact, I just looked at one of these images and saw for
the first time in a satellite photo the new location of lakebed runway 03-21 that I thought I had discovered during my flyby on 14 June 2010 (my photo
below, second photo is from heavily edited Ali data), but then learned had been noticed before (supposedly in satellite photography, though I've
never seen the photos).
Above: My aerial photo of the new location of lakebed runway 03-21 from 14 June 2010
Below: Heavily edited (from a screenshot, no less) image showing (faint, below other lakebed runway) image of the new location of lakebed runway 03-21
from Ali imagery on 25 February 2010.
So there are mountains of data available to peruse and analyze. BUT, there are a few challenges....
1. Files are very large. One Hyperion "snapshot" of a swath that includes Papoose Lake is going to be a 250+ MB download. Uncompressed, the dataset
is going to be as big as 1.5 GB.
2. Good luck with file formats. The fact is, if you're not a "computer person" then you aren't going to be able to do anything with this data--in
fact, you probably won't even be able to extract it (continued below)
[edit on 20-8-2010 by shmuu]