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How Google Earth Images Are Made
An anonymous reader writes "The Google Librarian Central site has up a piece by Mark Aubin, a Software Engineer who works on Google Earth. Aubin explains some of the process behind capturing satellite imagery for use with the product. 'Most people are surprised to learn that we have more than one source for our imagery. We collect it via airplane and satellite, but also just about any way you can imagine getting a camera above the Earth's surface: hot air balloons, model airplanes - even kites. The traditional aerial survey involves mounting a special gyroscopic, stabilized camera in the belly of an airplane and flying it at an elevation of between 15,000 feet and 30,000 feet, depending on the resolution of imagery you're interested in. As the plane takes a predefined route over the desired area, it forms a series of parallel lines with about 40 percent overlap between lines and 60 percent overlap in the direction of flight. This overlap of images is what provides us with enough detail to remove distortions caused by the varying shape of the Earth's surface.'
My bad.
I sure wish Google Earth had a way to adjust the brightness/contrast of individual tiles or maybe the view window. Some areas are very dim and need brightness/contrast adjustments.
Anyone who has thought about this for more than half a second, or has looked at anything more than just their backyard would realise that it is cobbled together from various sources.
Engineering is the art of compromise.
Not to mention those different copyright notices on different parts of the world
This makes it sound like Google actually did this work themselves with mental images of Googlites flying kites and riding hot air balloons. That is patently untrue. Most of the images in Google earth have come from other sources (government agencies, scanned aerial photos, etc).
Engineering is the art of compromise.
Maybe you should download and try Google Earth which....
requires 3D hardware, can do smooth zooms, tilts, and pans, and showa the world with elevation.
Google Earth IS the evolved version of the Keyhole client you referred to.
Actually according to our most detailed imagery, your ass isn't shiny and contains only about 1% metal, mostly calcium, potassium, sodium and magnesium ions. -Google team
Actually there's no need for a camera's "panoramic" mode any more. Check out Autostitch , a free for personal use program created by researchers at UBC. Essentially you take as many pictures as you want with varying amount of overlap. Each picture can be rotated differently and even vary somewhat in exposure, and this program automatically figures out which ones go where, even throwing out ones that are not part of the scene. It takes a ton of ram and some CPU speed but the result is better than any other method I've seen. Some examples here at the bottom of this page: AZ Snow Pictures.
4275 Athens-Boonesboro Road, Lexington, Kentucky 40509
r ls=en&q=4275-athens-boonesboro&btnG=Search
y j8t&style=o&lvl=2&tilt=-90&dir=0&alt=-1000&scene=2 023607&encType=1
Seems an appropriate opportunity to ask the question: Why the fuck is this residence blurred out? It appears to be someone who is a planholder in Kentucky's state health care plan, so maybe they're a powerful state government official:
http://www.google.com/search?hl=en&client=safari&
BTW, why are the addresses of all Kentucky state planholders publicly available and indexed on Google? That is just pathetic data security...
Anyway, the same address is accessible (and not blurred) via Microsoft Live!:
http://maps.live.com/default.aspx?v=2&cp=q9wwps7y
And appears to show two residences with pools in the back yard. Nothing to hide. Property records indicate that they were formerly owned by a lawyer named William Hurt, who practices in Lexington but now lives at another address. Given the rather inconspicuous pictures of them at the Microsoft Live flyover, the fact that they're blurred out on Google Maps is even more conspicuous than just showing the pictures of the two houses that are blurred.
There may be a high-powered state government official living there, but how did they have enough influence to get the pics blurred out? Were they skinnydipping in the pool? I don't think the map would show enough detail to make that a problem. Any ideas?
Unfortunately, when working with that kind of imagery collection the high tech part is on the processing end.
You need to:
1. Correct for lens distortion
2. Correct for tilt
3. Correct for terrain distortion
4. Correct lighting imbalances across the scene
5. Assign it bounding coordinates of a known mapping coordinate system / projection
This is the basic process for making an orthophoto. These are generally dealt with using a software package like Erdas Imagine which can deal with all the steps in one swoop. It looks at the lens info, coordinate tie down points, an elevation model and outputs a photo that can be used for linear measurements.
So anyway, it is possible to accurately georeference many sources of imagery, it just depends how much time you want to spend processing it. If you plan on covering a large area, taking photos out of the window of a Cessna is probably not the best way.
Google Earth used to be cool, but it's turning into one massive billboard (perhaps one of the ideas all along). In Sydney for Australia Day, Google (and whatever the Microsoft's copy of it is called) did flyovers with huge pre-publicity. People lay out banners, .com wannabees stuck huge logos on their rooves, people picnicked and love-maked all on the hope of becoming 'famous' (with four million other people). Google put it up and at the end of the day, Sydney wasn't Sydney any more. Instead, Sydney was transformed into one big banner ad:
- day-flyover/
n s_demolished/page2.html
http://googlesightseeing.com/2007/02/27/australia
Then we had the world's biggest photojournalism fakery with Google restoring New Orleans to pre-Katrina. Beyond weird. Did they think the residents wouldn't notice?
http://www.theregister.co.uk/2007/04/02/new_orlea
Google Earth is sponsored infotainment. If you'd like to see Earth without the Ads, there's a little mob called NASA I hear are going places: http://visibleearth.nasa.gov/
If you think a regular flight is boring, you have never been the pilot on a picture taking flight:
1. You fly straight (GPS and autopilot) for half an hour, then
2. turn around, and fly back.
3. Repeat this until the fuel is used up.
4. Refuel and repeat.
The only fun thing to do is when you turn: with the google photographer on his stomach with the camera, you do a Chandelle or Wing-over http://en.wikipedia.org/wiki/Aerobatic_maneuver This gives you a few seconds of weightlessness, and with the photographer in the back now floating in the cabin, he smacks on the floor with an "ooommpf" when gravity is reapplied.
The first few times he complains, but you just tell him you have to do this to properly align the aircraft for the reverse leg of the flight pattern.
So the routine for the photographer is something like:
1. click, click, click, click, click, click, click, click, click, click
2. "Whoooooooooo, ooommpf"
(I wonder if he reads this?)
don't cut it off www.mgmbill.org
I thought film was dead too (or rather, I thought it should be), until we recently had to order 40k acres of imagery at six-inch-pixel resolution, and I talked with the folks who own the cameras and fly the planes.
When it comes to airplane-based commercial aerial photography, film remains the most wide-spread capture medium. A decent camera can easily cost more than $1 million -- and you'll probably want two to capture stereo pairs, and don't forget a spare. For now, digital cameras are no less expensive and offer few benefits over their film-based bretheren.
Both require a GPS-controlled platform, capable of shooting several shots a second. After scanning, typical film-based photography is for all intents and delivers a 250+ megapixel result -- the digital alternative to such a beast is not exactly easy to find, and definately not inexpensive. Those are big files tool, and lossy compression is a bad, bad thing. Given the cost of fuel these days, redundancy is essential when it comes to data. That means being able to store four-to-twelve uncompressed (or minimally) 250+ megapixel images on two systems of one type or another, both of which must be rugged enough to withstand their environment.
Last but not least are the lenses. Outside the world of physics research, the highest quality land-camera lenses, even those in the cinematagraphic world, exhibit far more distortion than is acceptable for survey-grade aerial photography.
So, you're right. And yes, it sucks. We're betting environmental regulations will probably be the nail in the coffin over the next decade.