About Google Earth Imagery

You would be surprised how many people initially think Google Earth will show imagery in real-time. Or, that surely it will only be a day old. I guess part of this thinking comes from watching the weather satellite photos which are only a few hours old, or live weather radar. But, the problems of getting high resolution imagery are very challenging. Weather satellites are at geosynchronous orbits (36,000 km). High resolution satellites (like those operated by DigitalGlobe) operate just a few hundred kilometers above the Earth. This means they only see a small part of the Earth with their camera as they orbit over. They typically go around the Earth every 90 minutes, but only cover about 1% of the Earth on each pass (you can see strips of imagery if you look at the imagery in Google Earth) – most of that is water. Not only that, but imagery for Google Earth is only going to be good if the sun is at a high angle when the satellite goes over (fewer shadows), when there are no clouds, and as little haze/pollution as possible. Believe it or not, the times when these factors all come together are pretty rare.
Once the imagery is taken, it takes time to process the data by a commercial provider like DigitalGlobe before it is available to customers. Google is one of these customers. Google has to evaluate the new imagery against the current imagery to determine whether the new is better than the current. I assume they are trying to automate as much of this as possible. But, for important areas with large populations the process most likely involves people. This necessarily takes quite a bit of time – especially when you think about the quantities of land mass of the Earth. Once an image is selected, it has to be processed into the format and coordinate system of Google Earth’s databases. Then it has to go through a quality control process and fed into a processing system before it gets distributed to the live Google Earth database servers. This is one reason why you usually do not find any imagery younger than about 6 months in Google Earth. And why updates only happen about once every 60 days.
Not all the imagery in Google Earth comes from satellites. A lot of the imagery comes from aerial photographers mostly in airplanes with special high resolution cameras. Some of the imagery even comes from kites and balloons. Google acquires imagery from a variety of providers. Some of the imagery is given to Google by city or state governments. The age of the imagery varies greatly, but most of the high resolution imagery is between 6 months and 5 years of age. Again, because the imagery comes from a variety of sources, the process to get this imagery into Google Earth is complex and involves a great deal of time and effort.
Another reason why you don’t find imagery that is newer is that it can cost a great deal of money to acquire quality aerial imagery. The companies who spend this money need a way to recover their costs. More recent imagery is more valuable than older imagery. As a result, these companies are reluctant to have their newest imagery available for free for anyone to view in Google Earth. Read the agreements for Google Earth before you try to use its imagery for business applications (more information). You can’t sell or use the imagery from Google Earth for business purposes without permission.
However, near real-time imagery of Earth is available in Google Earth! “What?! After all that you are saying it is available?” you ask. Sure, first there’s the new Clouds layer. Found under the new Weather layer folder. The clouds are actually taken from weather satellites and are a global picture of the clouds as recent as 3 hours old. Ok, so that’s not the kind of imagery you meant.
Daily Planet Imagery by NASA in Google EarthNASA has a layer they call DailyPlanet which shows the entire Earth at a medium resolution (about 250 meter resolution per pixel). You can view DailyPlanet in Google Earth . The imagery is taken by the MODIS Terra satellite and is processed as quickly as possible and shows the entire Earth between 6 – 12 hours old. The imagery is continuously updating. When you download the network link above you see the Earth with clouds. Clouds may not line up properly because the satellite has to make multiple passes to get a full picture and the images have to be spliced together. As you zoom in, you will see higher resolution imagery load – up to a point (since this is medium resolution imagery). Remember the fires in California last October? You could have watched the smoke visible from space with this layer (except the layer just became available in December). You can see dust storms, large fires, volcanoes, haze conditions, droughts, floods, and – of course – clouds. Right now, this layer from NASA is the most recent, highest resolution imagery of the Earth continuously updating available to the general public.
Anyway, I hope this article helps provide a better understanding of the imagery in Google Earth and how it all works. This is a high-level overview and is based on my own observations and opinions. Feel free to comment below.

About Frank Taylor

Frank Taylor started the Google Earth Blog in July, 2005 shortly after Google Earth was released. He worked in 3D graphics for many years and was very impressed with this exciting product. Frank left in 2009 to circumnavigate the earth by sailboat as part of the Tahina Expedition.



Comments

  1. Great post. I’ll probably be pointing people to it for years to come, as I hear these kinds of questions pretty often.

  2. Frank,
    The question that I keep getting over and over and over and over and over is how do we tell how old a particular image is. I keep seeing people refer to “oh that image is from 2006″ or “that’s 6 months old.” How do they know?

  3. I have to agree with the comment above, this is a great post, hopefully people will read it and learn that not collecting hi-res imagery from space is not easy.

  4. Dude,
    People use various things that do or don’t show up in images to estimate date. For instance, if a new house is built in a neighborhood but doesn’t show up on the imagery, You know that image can’t be very recent. Or, if road construction is going on in the imagery, it’s fairly easy to date it if you know when that construction would have been taking place. You can use other methods to determine these things too, such as looking for leaves on trees (winter vs. summer) to narrow it down to a specific time.

  5. Ernst M. Kofler says:

    Great post, Frank!

  6. Great Post Frank! It’s always great to read what you are digging up here regarding Google Earth. I have a huge directory of KML files that need to be looked at in GE, and most of them have come from here. So, thanks!
    I almost wonder if the attitude of people thinking that the imagery in GE is real time stems from popular culture. Specifically, I’m thinking of a part of a Simpsons episode where Marge zooms into her house and finds Homer sleeping in a hammock in the back yard in a scandalous fashion. Little references like probably influence people’s perceptions. Just a thought.
    @Dude: I think one way people can determine the date of the imagery is simple imagery interpretation. For example, if someone zooms into their house and sees a car that they don’t have anymore but can specifically recall when they have it. Details like that would provide a useful range for when the picture was taken. Obviously, though, you couldn’t get an exact date, but still.
    Just my $.10.
    Cheers!!

  7. Agree with Dude: It continues to be a rotten shame Google won’t bother to publish a vector layer like the Digital Globe set that would list the date each imagery “subarea” was taken, remote sensing source, and date added to Google Earth. They surely have a back office system that tracks this. What’s the harm in letting users know more about what we see? In the absence of facts, everyone I know disregards it as just a dumb, unpredictable, and often misaligned backdrop graphic. But then again Google’s entire system has ducked decades of work on metadata standards.

  8. This is the first full explanation of the imagery process for Google Earth that I have read but it still annoys me when I load the Digital Globe layer and seeing rectangles of 0% cloud cover imagery over areas which do not have high-res coverage yet. I’m still not sure if Google has a whole database licence or if Google buys the imagery depending on what it is.

  9. guinevere harrison says:

    Well done setting the record straight, Frank. And as always, in clear language that us non-developers can understand!
    I think people also assume that satellites are like digital cameras, continuously streaming ready-made photos down to Earth. As I understand it, a lot of of them are multi-spectral sensors picking up data that we can’t even see with the human eye (infrared, for example). Many of those NASA photos of the San Diego fires were actually false-color images. That is, someone had to process the image to make it *look* like a photograph—it didn’t just appear that way naturally.

  10. Much of the imagery (at least for North America) has actual dates attached, right within Google Earth. Look in the layers, under More->DigitalGlobe. If you play around with various years/cloud cover layers, you’ll see the rectangular sections of imagery as they were taken.
    Now, the only trick is, a particular area might have several dates attached – you can click on the actual label and go to a preview of the imagery in your browser – DigitalGlobe uses this preview function to sell the original imagery, if you’d like. Take a close look, see if the seasons/cloud cover match to what’s actually displayed in GE, and 90% of the time you will be bang-on.
    I live in a city (Calgary, Canada) where we literally have changes to our roads and buildings daily, and this method has so far worked with every imagery update. Some of us who track development know to within a week when things change, and the DigitalGlobe dates are accurate if you are careful.
    Maybe Frank could write an article for GEblog that covers this a bit clearer than I did :)

  11. It’s true that the new layer became available last December, but not forget that Aqua and Terra layers have been availale for a few years. They’re updated daily too, the only difference is that Daily PLanet is a global mosaic, whereas Terra/Aqua have only some parts of the Earth surface – the rest is black/transparent.
    Another interesting feature is the MODIS archive – you can go back in time and see the Terra/Aqua images from all the days back to 2004-12-25. So anyone can still see the California fires. To do so just use time parameter (time=YYYY-MM-DD) in WMS request – you need some WMS client program with time support or World Wind and this plugin http://www.worldwindcentral.com/wiki/MODIS_historical_image_layers_plugin
    Maybe something similar could be done for GE…

  12. If there’s nearly real-time data available, why not crowdsource the whole quality control and review process by letting people mark rectangular spots on the imagery which is good quality – just like the NASA crowdsourcing project of marking craters and “interesting spots” on Mars imagery?

  13. I was wondering who is in charge of changing the pictures. I have a project where we are building condo’s however the old plant( now gone ) is still in the picture.
    237 Monroe Street
    Saline MI 48176
    Any help for who to ask for an update photo would be great.

  14. I’ve worked for a satellite image distributor and the problem with displaying dates is that when you provide imagery from so many different sources, the dates can be incorrect on a relatively regular basis. For example, if you do a large aerial survey, it may take days or even weeks to take all of the imagery. However, when the data is delivered, it usually has one date attached to all of the data. Depending on the source though, most dates are accurate to within a month or two. I would say that dates associated with Digital Globe satellite data are accurate to the day.
    You also run into that issue when data passes through a number “middle men” before it reaches the customer. This seems to be the worst when private companies resell government data. I’ve seen differences of up to two years between two different companies selling government data when it was obviously the same picture.

  15. A friend said he chatted online, he’s in northwestern Canada, with a family member in Ohio, his brother said he read the name off a store sign (with Google Earth) across the road and also asked what the pipe in neighbors yard was, can this be possible? Was his brother looking at years old imagery? If it is possible even if not in ‘realtime’ then how does one access it?
    Curious in Northern Canada

  16. I was wondering if i could use an image from google earth for my High School year book cover?

  17. Hi there,
    Could you please tell me why it is that I can see the house my Daughter lives in in Melbourne, yet I have no hope of even getting any image of my house, we are about 130 Klm apart?
    Any area around where I live you just cannot see, it seems to show up as a green haze!
    Thank you
    Bert

  18. Lara Ghanime says:

    As part of the Sabis network of schools, I am working on editing and finalizing the new SABIS science books all affiliated schools will be using. We need permission to publish screenshots from google earth in our science books. We have included in the program a topic that discusses google earth and viewing possibilities and so for illustration we need to include screenshots. W need an answer before June 17, 2008.
    Thank you
    Lara
    Science Analyst

  19. Hi There,
    In the Netherlands there was a discussion about using infrared images made by planes for energy-saving advice. You can see if a roof is good or badly insulated. I was wondering what are the moste detailed infrared images available for public services made from space?

  20. Ian Bolton says:

    Does Google Earth keep older pictures that were previously published? There are parts of the world (e.g. the Orkney islands currently) obscured in cloud but I’m sure this was not the case a while ago. It would be very useful to revert to an older image.

  21. Richard Drevo says:

    Can anyone tell me exactly what the elevation levels are in Google Earth; i.e., are they mean sea level readings topological calculations, etc. ?
    Thanks

  22. Is it true that you can zoom any part of the world and see people as well as animal as they’re moving at that moment? Please let me know ASAP. My friend is interested in getting it if this is so.
    Thank you in advance for your prompt response.
    Enilda

  23. How do they get the street view images? The engineer I work with tried telling me they get those images from satellites but i dont think so. My friend told me he had seen a truck driving around with a lot of really nice looking cameras on it, is this what they use?

  24. Who takes all those 360 degree angle street view pictures? It’s kinda scary we live in a world where you can see your neighbors outside and when your house is right there.

  25. Does anyone know why an older photo would replace a newer one? I had construction done on my property in 2003, that showed in 2006 and 2007, but the view has now reverted to an older pre-construction view?

  26. Dear Sir good morning
    I like to inform you that in google earth the location of (Beit El Suhaymee-Cairo) is wrong this location is for (AHMED MAHER INDUSTRIAL HIGH SCHOOL) i lived in front of this place for 37 years.
    Now living in (Madinat Ash Shuruq) as per google earth But it should be (AL SHURUQ) means sun rising in arabic language.
    All the best regards
    WAEL KHAIRI AHMED

  27. I’m using Google Earth 4.3 now with troubles as it relates to the ‘cloud layer’. When I click the layer, my entire display turns into a ‘negative’ in black & white.
    How do I overcome this?

  28. ian foubister says:

    the clouds have been covering the Orkney Islands for three years .can’t you get a better ‘picture’?
    Ian

  29. jack murfin says:

    I get google earth in 8 bit colour, really just black and white. No matter how often I reset to 32 bit, as soon as I select google earth the 8 bit colour takes over. I’m running windows xp media edition. Any answers out there.
    Jack

  30. the particular part of East Anglia UK north of Wisbech cambs; is THREE years old. in Newton village trees that were removed in spring 2006 are still shown. houses built in january 2006 do not appear. this sort of time lapse renders GE pretty near useless.

  31. Mario Gisiger says:

    We are running a small family business in Seychelles on the Island of Praslin.
    Updating to google earth 5.0 we had to discover that our property is covered up behind a thick cloud.
    Is there a chance that in the very near future google will update its picture again and we get a clear few to our home/business again, (it toke google earth 5 years to update the last picture).
    We are very very sad with the release of this latest satellite picture.
    We included links from our homepage to google earth for our future clients to see what will expect them (location…) when staying at our place, but now the link will be worthless.
    Looking at other (business) location on the Island of Praslin, which are located all along the coast/beach, they are clear and not hidden behind clouds, its really just our spot.
    We hope you will look in to possibility to giving us back our view from the shy, which is for great importance for our business “Jardin Marron”
    With best regards,
    Mario & Marie

  32. I don’t know if anyone has already answered this question or if anyone is having problems to, but Earth wont show up on my screen. All my points that i saved to my google earth (old version) show up but nothing else does. no streets no images. can anyone help me?

  33. Juan Font says:

    Visualization of shallow oceanographic or marine geophysical data required vertical exaggeration ratios of 10 or more. Is it possible to increase the vertical exaggeration in Google Earth beyond the limit of 3 set in the preferences?. If so, how?. If not, why?. When will it be possible?.

  34. John Kesich says:

    From the above discussion, it appears that Google does not publish metadata for GE images, the most basic and useful of which would be when a specific image was taken.
    I suppose this may change if and when Google decides to add functionality to enable viewing locations historically.
    I am interested in seeing the impact of gas drilling on various regions in the US. There are a few instances (notably Sublette County, Wyoming) where people have used GE to create such documentation, but it would be nice to be able to pick any location and step back in time image-by-image through GE’s entire collection.

  35. Thanks for the info. I was confused, since my mother moved into a new home about 5 years ago this summer, and it STILL shows as a vacant lot on Google Earth.
    The service is free, so I’m not really complaining.

  36. Rune Lind says:

    I like Google Earth a lot. The only thing that bothers me is the very old pictures from Thailand. We have a house in Korat (Khorat / Nakhorn Ratchasima) and the house is visibly in GE pictures, but the houses around our house is not there and they was built for more than 8-9 years ago. I can understand now why some pictures are around 5-6 years old. But the pictures of our area is more than 9 years now.
    That is a little to slow Google!! :-)

  37. Jacy Alves de Brito Júnior says:

    hi. very clarifying.
    still I wonder if there’s a way to ask them to update (despite all difficulties exposed above) the images of my hometown in Brazil, because they date as far back as 2003. Thta’s too old and the area has changed so much, and its dissapointing to see an ancient image of it beeing broadcast all over the world.
    thanks
    jacy brito
    Mineiros, goias, brasil

  38. thanks for the information.I need your help.I have been confused by a question for a long time.you know,some image of Google Earth come from QuickBird.I want to know how the QuickBird image become the part of GE.in other word ,i want to know the processing prcedure.

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