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How Google Earth Images Are Made

Posted by Zonk on Sun Apr 29, 2007 09:41 PM
from the it's-all-in-the-f-stop dept.
Businesses Google The Internet Science Technology
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.'
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  • Really? Most people are? (Score:4, Funny)

    by Anonymous Coward on Sunday April 29 2007, @09:46PM (#18923381)

    "Most people are surprised to learn that we have more than one source for our imagery." Must be people who never leave the US border? How can you possibly miss what a hodge-podge of a patchwork Google Earth is? It's especially apparent if you zoom in on a small island.

    • Most people don't think. Period. (Score:5, Insightful)

      by EmbeddedJanitor (597831) on Sunday April 29 2007, @09:56PM (#18923439)
      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.

      • Re:Most people don't think. Period. (Score:5, Funny)

        by glwtta (532858) on Monday April 30 2007, @12:35AM (#18924259) Homepage
        Dude, you find the oddest shit to be all superior about.

        • Re: (Score:3, Interesting)

          by Bob-taro (996889)

          Dude, you find the oddest shit to be all superior about.

          Well put. If a story came out that ... I don't know ... Osama Bin Laden was once a woman, you can bet someone would post "Am I the only one to whom that wasn't patently obvious?"

          The funny thing is, the "patchwork" appearance of less populated areas on Google earth is probably NOT evidence of the photos coming from different sources. You can get very high resolutions [wikipedia.org] from satellite imagery. I always assumed the low-res areas were due to storage lim

      • 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.

        Not only that, but the article strongly implies that Google itself is obtaining the imagery - which is not the case. They buy (or license) imagery from a wide variety of sources. (The folks who take these images tend to retain the rights to them - and resell the imagery as many times as possible.)
      • There's a road going north from here which fades out, reappears 20 yards to the left for 100 yards or so, fades out again and goes back where it's supposed to be, etc.

        Then there's the difference between the terrain height and the images - big lumps in the middle of the sea.

    • Not to mention those different copyright notices on different parts of the world

    • We? (Score:5, Insightful)

      by EmbeddedJanitor (597831) on Sunday April 29 2007, @09:59PM (#18923469)
      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).

      • Re: (Score:2, Insightful)

        by stoicio (710327)
        Yes, I agree. There are huge glossing statements that make
        it sound like google actually acquires data.
        This engineer has only a vague idea of how airborne and satellite
        imaging work.
      • Pfff, the government works for google. We allllll work for google, just with varying degrees of separation o_o

        Anyway, yeah, it does sort of make it seem like that. "Oh yeah, we just take some kites with cameras on them, and set up a good delay. Ya know, like 30 seconds or so, eh? Then we launch it up real good, and when it comes down, sometimes it's a real good picture, yaknow, eh?"

        Apparently they're all Minnesotan or Canadian.

      • Re:We? (Score:4, Funny)

        by laejoh (648921) on Monday April 30 2007, @01:39AM (#18924533)

        ... with mental images of Googlites flying kites and riding hot air balloons...

        My mental images consist of Googlites duck taped to the bottom of 747's holding a digital camera...

    • I thought it was all satellite mapping. (for one, the copyright notices usually say 'telesat'). The fact that a lot of it is aerial never occurred to me. However, it makes more sense that the high res photos, at least, are taken from other platforms than satellites.

  • Oops - my bad (Score:5, Funny)

    by SpeedyDX (1014595) <speedyphoenix@@@gmail...com> on Sunday April 29 2007, @09:47PM (#18923387)

    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.
    So THAT'S what the creepy guy in front of the elementary school near my house was doing with the kite and camera. They need some uniforms. I called the cops on that guy. Boy, I bet he had a great time trying to explain himself.

    My bad.

    • 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.

        So THAT'S what the creepy guy in front of the elementary school near my house was doing with the kite and camera. They need some uniforms. I called the cops on that guy. Boy, I bet he had a great time trying to explain himself.

      My bad.


      Hey, don't worry about it, dude. I'm used to it at this point. It was just nice to get out of the house and fly the kite, even if I did get hassled by the cops. By the way, you should really have that mole looked at. And, tell your wife to go with the blue one.

      • Re: (Score:2, Funny)

        by Anonymous Coward
        No, he meant the schoolgirls should have uniforms, 'stead of those loose-fitting low-cut tops the guy was looking down.

      • Re: (Score:2, Insightful)

        by Anonymous Coward
        Things are very bad. When was it ever a problem to be taking pictures near a school? In 2000, I worked with a photographer who did freelance work for a local newspaper. He related a story to me about being "hassled" by the police a few years earlier. He parked outside of an elementary school while waiting for his kids to get out. He grabbed his camera and started photographing some of the trees in the area, as it was Autumn and very colorful in the area. Which almost always gets printed in the paper f
        • Being in a public street with a camera is one thing, but flying a kite with a camera attached over private property (or a school, if you don't count that as private property) is another.

          Sure, some cops go overboard like in your example, but I don't think a friendly policeman approaching our kite flying camera friend and asking for ID just to make sure he's not on a list of registered sex offenders or anything is going overboard.

          We had a policeman knock on our door a few years ago. A car vaguely matching the

          • Re:Oops - my bad (Score:5, Insightful)

            by Eivind (15695) <eivindorama@gmail.com> on Monday April 30 2007, @01:50AM (#18924595) Homepage
            Perhaps, but one problem is that its the same people who are "suspicious" every time, so what may seem reasonable to all outsiders, because whatever behaviour looks fishy, may be a constant nuisance of having to defend ones own perfectly legal actions over and over and over to cops.

            I know a guy, originally from Pakistan, wears typical street-kid clothing, is passionate about biking and have a $10K bike.

            He *literally* has to "explain himself" once a week or more.

            By the 20th time a cop pulls you over and demand that you explain how the hell you're allowed to ride a bike that you, infact, own, you tend to stop thinking that its all that reasonable.

            The problem offcourse is that each individual cop doesn't know that X other cops *also* pulled the guy over this year, so to them it seems reasonable and so its hard for them to see why he can be annoyed and impatient about it.

          • We had a policeman knock on our door a few years ago. A car vaguely matching the description of ours was seen leaving the scene of a grass fire. He was quite friendly, explained why he was there, asked if we'd been anywhere recently (I assume he would have put his hand on the bonnet of the car too just to check), chatted about the weather, and then left. Just the way it should be.

            You're right, that's "Just the way it should be."

            I assume you're from the UK, because you used the word "bonnet." I've heard about your friendly neighborhood constables. Unfortunately, in the US, most (not all) cops are on a power trip, and are more interested in harassing whomever they have an excuse to harass, than gaining the respect of the (generally) law abiding public, and preventing real crime.

      • I probably would have called the cops too. At least they can wander over and have a quick word to make sure everything is legit.

        Maybe it is just me but if something looked fishy (and for me someone putting a camera on a kite is more geek than pervert) I would just have asked him what he was doing.

  • Some tiles too dark (Score:5, Insightful)

    by Derling Whirvish (636322) on Sunday April 29 2007, @09:55PM (#18923437) Journal
    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.
  • A friend of mine is a local flight instructor and has done a few flights for Google Maps crew. Perhaps they were just doing specialized by-request work, but in this case it was a dude with an SLR and a big lens shooting out the window of a Cessna.

    I was skeptical too, but that’s what he tells me.

    • Re:Not always so high tech (Score:5, Informative)

      by dickeya (733264) on Sunday April 29 2007, @10:46PM (#18923751)
      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 [wikipedia.org]. 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.

  • Tidbits if you're interested (Score:4, Informative)

    by Anonymous Coward on Sunday April 29 2007, @10:30PM (#18923671)
    I was one of the Aerometric-Alaska flight operators that took photography in 2006 while on-board a variety of small planes. The film we used was generally Kodak 2444, with 9' x 9' shots. After development, these prints can then be scanned at a resolution comparable to roughly that of an 11 megapixel camera. As the article states, these photos are usually taken in succession with 60% overlap. This is what has allowed people to generate topographic maps for decades, even before complex computer interpolation and computer graphics capabilities were present. Stereoscopic perspective of the same area of land taken from 2 separate angles allows people to determine differences in height, in case anyone has ever wondered how that worked. Nowdays, surveys and digital radar scanning is where most of the information that modern topography uses tends to come from.

  • Blurred residences on Google Maps in Lexington, KY (Score:5, Interesting)

    by Anonymous Coward on Sunday April 29 2007, @10:42PM (#18923727)
    4275 Athens-Boonesboro Road, Lexington, Kentucky 40509

    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&r ls=en&q=4275-athens-boonesboro&btnG=Search [google.com]

    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=q9wwps7yy j8t&style=o&lvl=2&tilt=-90&dir=0&alt=-1000&scene=2 023607&encType=1 [live.com]

    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?

  • Earth is one big billboard (Score:5, Interesting)

    by BillGatesLoveChild (1046184) on Sunday April 29 2007, @11:12PM (#18923859) Journal
    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:

    http://googlesightseeing.com/2007/02/27/australia- day-flyover/ [googlesightseeing.com]

    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_orlean s_demolished/page2.html [theregister.co.uk]

    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/ [nasa.gov]

    • Re: (Score:2, Informative)

      by xenn (148389)

      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:
      that's funny, in the link you provided they say this:

      So, after hours of combing through the new images, we've found no real examples of private advertising or even any sign that the people of Sydney knew they'd be on Google Maps!

    • Due to weather and difficulty getting local permissions, Google was only able to capture a small part of the Sydney area they planned, and at different times than they'd stated, too.

      As a result, there's no user-created ads visible at all in the new imagery, anywhere.

    • Idiot (Score:3, Insightful)

      by Snaller (147050)
      "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?"

      No, they thought they were intelligent adults instead of idiots. Nowhere in the world is the completely correct (surely not around here) BECAUSE ITS NOT REAL TIME. They get the best quality which is fairly close. Those of us with 3 digit IQ's understand that.

      "Google Earth is sponsored infotainment. "

      Indeed, if you want to find a pizza place you

  • This is not new (Score:4, Informative)

    by ouzel (655571) on Sunday April 29 2007, @11:56PM (#18924055)
    The process he described is the same process that imaging companies have used since LONG before Google Earth acquired Keyhole. And many of those companies are still doing it. In fact, many of them are the same companies from which Google is now acquiring the imagery used in Google Earth. Does this guy really believe Google is conducting their own overflights and sending up their own balloons? Does Google now have their own satellites, too?

  • Weighless google photographer (Score:5, Funny)

    by viking80 (697716) on Monday April 30 2007, @12:31AM (#18924241) Journal
    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 [wikipedia.org] 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?)

  • They use a film camera??? (Score:4, Interesting)

    by gsasha (550394) on Monday April 30 2007, @12:47AM (#18924313) Homepage
    I'm extremely surprised they don't use a digital camera these days. Digital has great quality, and a full-frame digital back of the likes of Mamya, while expensive, pays for itself very quickly if you shoot a lot (and they appear to be doing so continuously). Besides, there would be no need to develop the film and scan it.

    Any ideas why they do so?

    • Because (AFAIK) digital cameras don't exist in the large format form factor that [film] cameras for aerial photography uses. Even if they did, from typical aerial photography altitudes digital camera are inferior in resolution to existing films.

    • Re:They use a film camera??? (Score:5, Interesting)

      by eggegg (754560) on Monday April 30 2007, @02:57AM (#18924899)
      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.

      • Re: (Score:3, Informative)

        by hughk (248126)

        Both require a GPS-controlled platform, capable of shooting several shots a second.
        Funny that, aerial mapping has been used for a looong time and before GPS. All you needed is a reference point with coordinates and then the rest follows. The old equipment used to put altitude, speed and direction onto the film for later use. Some cameras would take frames but some would in effect take a continuous strip using line-scan techniques.
  • I was on vacation in Malaysia last year. So, of course, I checked out the tropical paradise island I had been to when I came home. To my my surprise the island had disappeared in those few months, it was no longer available in Google Maps. Q: Should I have more baseless destinations in the future?

  • Do no evil my ass! (Score:5, Funny)

    by Jugalator (259273) on Monday April 30 2007, @01:39AM (#18924531) Journal
    So Google is basically saying that anyone willing to help them out can go fly a kite?

    Hmpf.
  • I have a 10Mpixel camera and an airplane. If I took a bunch of photos from an area not yet covered by them, would they add them to their Map/Earth for free? Cause flying around and taking photos isnt a great expense - its the processing and orthorectification...

  • Obligatory quote... (Score:4, Funny)

    by Vexler (127353) on Monday April 30 2007, @08:52AM (#18927033) Journal
    Deckard: Enhance 224 to 176. Enhance, stop. Move in, stop. Pull out, track right, stop. Center in, pull back. Stop. Track 45 right. Stop. Center and stop. Enhance 34 to 36. Pan right and pull back. Stop. Enhance 34 to 46. Pull back. Wait a minute, go right, stop. Enhance 57 to 19. Track 45 left. Stop. Enhance 15 to 23. Give me a hard copy right there.

    • Re:Powers of ten? (Score:5, Funny)

      by Anonymous Coward on Sunday April 29 2007, @10:14PM (#18923571)
      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

    • Re:My digital camera does the same thing. (Score:5, Informative)

      by kefler (938387) on Sunday April 29 2007, @10:32PM (#18923679)
      Actually there's no need for a camera's "panoramic" mode any more. Check out Autostitch [cs.ubc.ca], 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. [sabinovalley.com]
      • There never was as all panoramic mode does is crop the image on film to a strip rather than the full frame 35 or 24 mm. If you wanted genuine pano, you either used a panoramic camera which exposed three frames worth of film in one shot, or you took multiple shots with the help of Nikon's tripod adapter that had detents which matched up with several of their lenses (55, 110mm, and IIRC 200mm) focal length. Shoot, move to next detent, etc. I've done 360deg panoramics with that thing. It's awesome..
        -nB
      • The camera's mode, at least in Canon's case, is to show an overlay of the pictures already taken in the matrix or panorama you're taking. It's easier to get good, overlapping, easy-to-stitch images if you use the camera's framework to help you set up the shots, and be sure when you've taken enough to fill the planned matrix. As a bonus, the pictures are all tagged as to their position in the final photograph, and all the camera data is recorded for the stitching program.

        IIRC, the actual stitching still ha

    • Re: (Score:2, Insightful)

      by Anonymous Coward
      You missed the point, genius.

      Google does more than just stitch the images together. The seemingly excessive overlap is used not only to stitch, but to correct for geometric errors of perspective.

      Somehow, I doubt your camera does that too.

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