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How Google Earth Images Are Made 122

Posted by Zonk
from the it's-all-in-the-f-stop dept.
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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How Google Earth Images Are Made

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  • by Anonymous Coward on Sunday April 29, 2007 @10:46PM (#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.

    • by EmbeddedJanitor (597831) on Sunday April 29, 2007 @10:56PM (#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.
      • by glwtta (532858) on Monday April 30, 2007 @01:35AM (#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

      • by DerekLyons (302214) <fairwater@nosPam.gmail.com> on Monday April 30, 2007 @03:27AM (#18924765) Homepage

        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.)
        • When google maps first added the aerial imagery (and Keyhole had not yet been bought out and changed to Google Earth), I remember someone sharing it with me an being excited about seeing their house from space.

          At this point I had already seen and played around a bunch with Microsoft Terraserver and the USGS imagery, so I realized pretty quickly most of the places I was looking at were identical to the USGS aerial photos. It didn't take a rocket scientist to figure out these pictures weren't all taken fro
          • Re: (Score:2, Informative)

            by JayBat (617968)
            By the way, the thing that boggles me about all the mapping services out there is how they do routes: how do they determine where the roads are (DOT?), how do they store the roads, and how do they calculate driving routes (that often appear to take into account traffic speeds).

            A company called Navteq [navteq.com] does a lot of it, and contracts out data and software.

            The New Yorker had a great profile on E-mapping and route finding [newyorker.com] including a ride-along with a "Ground Truth" team that heads out with their GPS-linked

          • By the way, the thing that boggles me about all the mapping services out there is how they do routes: how do they determine where the roads are (DOT?)

            An amazing amount of data is available for free (or for a nominal sum) from various govermental bodies. There's even a standard format for it.
        • by rofthorax (722179)
          I like the painted lake and golf course near Google headquarters.. I haven't visited in a while, but after seeing features like that, I realized that some parts of google earth are painted.. My hometown, Los Alamos, NM had no detail for a while in the residential and governmental sections.. It does now..

      • 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.

    • by Wonko the Sane (25252) * on Sunday April 29, 2007 @10:59PM (#18923467) Journal
      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 @10:59PM (#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.
      • Re: (Score:3, Funny)

        by alisson (1040324)
        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 @02:39AM (#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...

        • Re: (Score:1, Funny)

          by Shadowruni (929010)
          It brings a whole new meaning to "I'm a leaf on the wind."
        • by jsindell (470747)
          I like to think of Googlites, like, with giant eagle's wings. And singing lead vocal for Lynyrd Skynyrd with, like, an angel band. And I'm in the front row and I'm hammered drunk.
    • 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.
    • "Airplane" was a comedy movie so i guess they meant that they filmed it with the same cameras that they used for "Airplane"
    • by Bazar (778572)
      I think what he actually meant, was that Google uses more then 1 medium to collect the images
  • by SpeedyDX (1014595) <speedyphoenix@NOSPAm.gmail.com> on Sunday April 29, 2007 @10:47PM (#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.
    • by forkazoo (138186) <wrosecrans@gma[ ]com ['il.' in gap]> on Sunday April 29, 2007 @11:57PM (#18923811) Homepage

      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.
  • by Derling Whirvish (636322) on Sunday April 29, 2007 @10:55PM (#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.

    • by dickeya (733264) on Sunday April 29, 2007 @11:46PM (#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.
  • by Anonymous Coward on Sunday April 29, 2007 @11:30PM (#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.
  • by Anonymous Coward on Sunday April 29, 2007 @11:42PM (#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?
  • I still can't see my house on Google Earth, all those corporations etc. complaining about how GE is showing a building site where there's now a building or wotnot and all I see when I look at the area I live in is a patch of blurry green. Sucks.
  • by BillGatesLoveChild (1046184) on Monday April 30, 2007 @12:12AM (#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.

    • by digitig (1056110)

      people picnicked and love-maked all on the hope of becoming 'famous'
      Any excuse...
      • by mgblst (80109)
        Great pick up line tho?

        Hey, so you want to be famous? Alrighty then, get your gear off.
    • 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 Monday April 30, 2007 @12:56AM (#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?
  • by viking80 (697716) on Monday April 30, 2007 @01:31AM (#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?)
  • by gsasha (550394) on Monday April 30, 2007 @01:47AM (#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?

    • by DerekLyons (302214) <fairwater@nosPam.gmail.com> on Monday April 30, 2007 @03:22AM (#18924741) Homepage
      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.
    • by eggegg (754560) on Monday April 30, 2007 @03:57AM (#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?
  • by Jugalator (259273) on Monday April 30, 2007 @02:39AM (#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...
    • You can add place points, and attach net based jpegs as overlays, you can adjust the size/angle/alpha.
      JUst split your images up and place them in the correct order, then publish the placeholders and any client will see your photos overlayed
      at the right location, if you did it right. I did this to one ski field that was mapped poorly, so I added a plane based aerial photo of it on top. Looks real good
      and great res, and png is not too large.
  • by Vexler (127353) on Monday April 30, 2007 @09:52AM (#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.
  • Antarctia is really badly mapped, I know its no amazon, but it would show of its beauty more.

    Hasnt Nasa mapped it well? Buy it google.
  • Does anyone know how often the maps get updated, or if ever? I started building my new home over a year ago, and have been living in it 7 months now, but the maps of the entire area are still obviously several years old. I know this because there are several entire neighborhoods that have been built up over the last 5 years that are not there either. This is on both Google maps and earth.
  • The Leonard P. Zakim Bunker Hill Bridge [google.com]

    I always figured there simply wasn't an adequate weather for a satellite flyover to get good pictures in a while, but if they can do it with planes, etc...

    Something of the magnitude of the Big Dig is a pretty notable event for a major city, and you'd think they would at least update it for Google Maps' sake. At this point it seems that the maps are correct, but the imagery isn't. Very misleading to those who "don't trust those computer mapping thingamajigs"

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