What the imagery dates really mean in Google Earth

As you probably know, when you’re looking at an area on Google Earth, the date the imagery was captured appears in the bottom center of the screen, as shown here:

dates

However, what does that date actually mean? As some of you have pointed out, the date doesn’t always correspond with the imagery (snow on the ground in July, etc).

For standard satellite images, it’s simply the date the imagery was taken, which makes sense. Easy enough. The discrepancies arise when Google loads imagery for a large area from a commercial aerial provider. In those cases, they’re given a range of dates for the imagery. The date you see on the screen is the “oldest known date” for that imagery, while the tic mark in the Historical Imagery sliders is the “newest known date”. In many cases, those date ranges can be up to a few months apart.
To confuse it further, some providers don’t even have exact dates for a batch of imagery; they might simply say “April-June, 2010″. In those cases, Google considers that to be “April 1 – June 30, 2010″, and then displays the date as explained in the previous paragraph.

While the system obviously isn’t perfect, it’s certainly improving. Google Earth didn’t start showing the date at the bottom until version 5 came out (so you had less of an idea of when the imagery was captured), and the Historical Imagery tool was certainly a great addition to Google Earth.

As the pace and quantity of imagery updates continue to increase, I expect we’ll see some refinements to this system over the coming years to help it become even more accurate and useful.

About Mickey Mellen

Mickey has been using Google Earth since it was released in 2005, and has created a variety of geo-related sites including Google Earth Hacks. He runs a web design firm in Marietta, GA, where he lives with his wife and two kids.



Comments

  1. It Looks Like Google Redid The Flight Sim In Google Earth.

  2. Wednesday says:

    Some versions of Google earth have the imagery date a day earlier than taken. For example, if the image was taken on 5/2/2005, the date on the bottom would say “5/1/2005″.

    Even more strange, if the image was taken on March 2004, the date would say “2/29/2004.” If the image was taken sometime in the year 2005, the date would say “12/31/2004″ (or 1/1/2005 on some versions)

    The older versions of Google earth (5.0 and earlier) were more accurate when it came to dates. It would say “May 2008″ instead of “4/30/2008″ and “2004″ instead of “12/31/2003″.

    • As plenty of default imagery is from the span of years you mention for “versions”, are you saying that the format of dates of imagery viewed, in say GE 7.1, will vary, or that the format is standardised for different versions so format may vary by the version of GE in use, say 6.1 ?

  3. Mickey – thanks for this helpful post about one of the most arcane features of GE, but not sure what the “tic marks” in the historic imagery sliders are, and would be grateful for clarification.

    Also, the 1993 date in the box on the screen shot would seem to relate to the earliest historic imagery, but is this always the case?

    Another interesting feature is that in my part of the world imagery dates appear when zoomed in to around 75 km eye alt and closer, currently 4/10/2013 (10 April) over a wide area, but switch to other dates on closer zooming. Does this reflect the loading of more that one layer of imagery?

  4. I want to know when new images will be coming down the pipe..If we can have some idea when an area might be covered with a fresh image. I’ve been waiting 7 years for my house to appear on images… I’m in the Philippines.

  5. Google should grab all the Ariel Photo Single Frames from the U.S.G.S, and release a massive historical imagery update for the U.S. I’m not saying they have to do it, I’m suggesting a neat Idea.

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