Historical Images

Introduced in version 5.0, Historical Imagery allows users to traverse back in time and study earlier stages of any place. This feature allows research that require analysis of past records of various places.[39]

The images are not all taken at the same time, but are generally current to within three years. However, with the release of Google Earth 5.0, it has historical images dating back to the 1940s in some spots. Image sets are sometimes not correctly stitched together. Updates to the photographic database can occasionally be noticed when drastic changes take place in the appearance of the landscape, for example Google Earth's incomplete updates of New Orleans following Hurricane Katrina, or when placemarks appear to shift unexpectedly across the Earth's surface. Though the placemarks have not in fact moved, the imagery is composed and stitched differently.

Place name and road detail vary greatly from place to place.

In some areas, local government jurisdictions have submitted more finely gridded terrain models through the Map Content Partners program.[71] In March 2010, the County of Marin, just north of the Golden Gate Bridge by San Francisco, California, published a 40 cm gridded terrain surface of 1425 km2 through the program.

The "Measure" function shows that the length of equator is about 40,030.24 km, giving an error of −0.112% compared with the actual value of 40,075.02 km Earth; for the meridional circumference, it shows a length of about 39,963.13 km, also giving an error of −0.112% compared with the actual value of 40,007.86 km.

On December 16, 2007, most of Antarctica was updated to a 15 m resolution using imagery from the Landsat Image Mosaic of Antarctica (1 m resolution images of some parts of Antarctica were added in June 2007); however, the Arctic polar ice cap is completely absent from the current version of Google Earth, as are waves in the oceans. The geographic North Pole is found hovering over the Arctic Ocean and the tiling system produces artifacts near the poles as the tiles become 'infinitely' small and rounding errors accumulate.

Cloud cover and shadows can make it difficult or impossible to see details in some land areas, including the shadow side of mountains.

How often does Google update the imagery in Google Earth?

October 4, 2010

This is a question that we get asked a lot, so hopefully this post will help clear things up.
The short answer is that Google usually updates imagery twice a month, typically around the 6th and the 20th of each month. We highlight all of those updates on the site as soon as we’re aware of them, like the one we recently covered on
September 21.
Each update covers a very small portion of the globe. For example, the United States might seen 4-6 cities updated, or perhaps a single state, and other countries receive similar minor updates. As part of each update, Google releases a
KML filehttp://www.gearthblog.com/images/gelogoicon.gif that shows all of the updated areas with red outlines, like this:

As a general rule, Google tries to keep every area updated to within around three years old, but that’s not always possible. However, if your area is more than three years old, it’s likely that Google is working on updating it soon.
That being said, we have no idea which areas will be updated next. We get a lot of specific questions such as “when will the imagery in Spokane, Washington be updated again?”. I promise you, we have no idea. The exception to that is when there is a major disaster, such as the
earthquake in Haiti or the wildfires in Boulder, Colorado. During and after an event like that, Google posts fresh imagery as quickly as they possibly can to assist in providing useful information to emergency workers and concerned residents of the affected areas.
Lastly, don’t forget about the historical imagery. We
recently showed you how the historical imagery is often fresher than the default imagery, so if you want to see the newest imagery of a particular location, the historical imagery tool might be your answer.
If you’re curious about the process used to capture and present the imagery in Google Earth, this
detailed post that Frank wrote last year will be very helpful for you.

Historical Imagery in Google Earth 5

September 29, 2010

I get a few emails every day regarding Google Earth’s “historical imagery” feature, so now seems like a good time to revisit the topic. Frank first wrote about this new feature back in early 2009 when it was released as part of Google Earth 5. I’ll leave his content below, as it’s a great introduction to how it works, but first we need to discuss one oft-overlooked aspect of historical imagery.

Historical Imagery can be newer

We mentioned it back in February of this year, but it’s important to realize that the newest imagery in Google Earth can often be found in this historical imagery feature.
Google is very careful about the imagery that they release to the default layer. If new imagery is good (but not good enough), they’ll often it put it in the historical imagery layer. Reasons why it might not be “good enough” can be due to some clouds in the way, haze/pollution, sun at the wrong angle (lots of shadows), and things of that nature. Despite whatever minor shortcoming it may have, the imagery still may be of value to you, so be sure to check for it.

How to use the Historical Imagery feature

Google already had more satellite and aerial imagery available for free than anyone. Now, they’ve added a new feature to new Google Earth 5 that let’s you turn back the clock and see other imagery they have for locations around the world. Click on the little “Clock” icon in the upper middle (or the “View->Historical Imagery” menu item). A time slider appears (see below) showing available imagery. If other imagery is available in your current view, you see little tic marks on the slider. Drag the slider (or click the left/right buttons) to see earlier or (or even newer) imagery.


For example, here’s a shot of the famous “
Bird’s Nest” stadium from the 2008 Beijing Olympics as it appeared under construction on February 17, 2007:


And, here is a video showing this all in action:

This feature is amazing! The amount of data Google is storing must be immense! Several instances of imagery for millions of square kilometers! You may be able to see how your house changed over the years, or see aerial pictures of cities from decades ago. Expect to see lots of posts on this new feature.
In addition,
Google has put up their own post with examples of historical imagery in action.
(
Originally posted Feb 2009)

New in Google Earth 5.0: Historical Imagery

Monday, February 2, 2009 at 1:00 PM

Google Earth has always aimed to deliver the most compelling and complete representation of the earth as possible. Until now, we have only been able to show a single image of any location. Displaying one image is fantastic for exposing the intricacy and majesty of our planet, but it reduces each location to a single snapshot and ignores the rich historical context of place.

With the newest version of
Google Earth we aim to fix this limitation by providing you with the ability to "go back in time" and observe changes to the landscape of our planet.

We have included an enormous amount of historical imagery in this first release, but you'll notice that most of the oldest imagery is concentrated in the United States. Adding imagery is an ongoing process, and we're continuing to add new places and new dates. We are very excited by what we have been able to put together for this release. We have included some fascinating old imagery, such as San Francisco in the 1940's or Las Vegas in the 1950's. We have also included a spectacular country-wide dataset covering the United States in the late 1980's and 1990's.

 

So now that you know the backstory, you're probably ready to dive right in and take a look. To transition to historical imagery mode, open up Google Earth 5.0 and click on the clock icon in the toolbar:



The historical imagery time slider will appear just beneath the toolbar. The time slider allows you to change your view to imagery which is older than the date shown on the slider. The tick marks on the slider represent images in our database that are available for your current view.


You can move the slider back and forth along the timeline or use the arrow buttons in the upper left corner to step from one date to the next. If there are just too many ticks marks grouped together try using the zoom in and zoom out buttons to expand or contract the timeline. That's all there is to it! Now you can fly around to different spots in the world and explore our archives to see what imagery we have to show of the location.

In addition to being just plain fun, historical imagery is a powerful tool for exposing changes to our neighborhoods, communities, and the environment. For years, the United Nations Environment Programme (UNEP) has used Google Earth to raise awareness about environmental change. Their
Atlas of Our Changing Environment has been a Global Awareness Layer in Google Earth since 2006, showing land cover change through a series of historical images. This imagery was served as a KML overlay and, while fascinating, could sometimes be cumbersome to use. With Google Earth's new Historical Imagery mode, we have brought much of this imagery directly into the client increasing the ease of use, availability, and exposure of this spectacular and revealing data. Check out the following tour, assembled by UNEP, highlighting the Aral Sea in Central Asia, where irrigation and water diversion has led to a dramatic shrinking of the lake beginning in the 1960s and continuing today.

But most of all Earth is about exploring and discovery; it's about gaining a new insight and a new view on the world we live in. In that spirit I'll end this post with one of my favorite examples of historic imagery which shows the amazing transformation of sports arenas in Philadelphia. Enjoy!

Technical specifications

Detailed release notes/history/changelog are made available by Google.[52]

Imagery and coordination

  • Coordinate System and Projection
    • The internal coordinate system of Google Earth is geographic coordinates (latitude/longitude) on the World Geodetic System of 1984 (WGS84) datum.
    • Google Earth shows the earth as it looks from an elevated platform such as an airplane or orbiting satellite. The projection used to achieve this effect is called the General Perspective. This is similar to the Orthographic projection, except that the point of perspective is a finite (near earth) distance rather than an infinite (deep space) distance.
  • Baseline resolutions
    • Czech Republic: 0.1 – 0.5 m (by Eurosense / Geodis Brno)
    • Slovakia: 0.5 m (by Eurosense / Geodis Slovakia)
    • Hungary: 2.5 m SPOT Images. Budapest approx. 0.3 m.
    • Germany, Switzerland, Netherlands, Denmark, UK, Andorra, Luxembourg, Liechtenstein, San Marino, Vatican City: 1 m or better
    • Balkans: 2.5 m (medium resolution)
    • U.S.: 1 m (excludes Alaska & Hawaii)
    • Global: Generally 15 m (some areas, such as Antarctica, are in extremely low resolution), but this depends on the quality of the satellite/aerial photograph uploaded.
  • Typical high resolutions
  • Altitude resolution:
    • Surface: varies by country
    • Seabed: Not previously applicable, but since the introduction of "Ocean", elevation data has been introduced (a colorscale approximating sea floor depth is "printed" on the spherical surface at views from high altitudes).
  • Age: Images dates vary. The image data can be seen from squares made when DigitalGlobe Coverage is enabled. The date next to the copyright information is not the correct image date. Zooming in or out could change the date of the pictures. Most of the international urban image dates are from 2004 and have not been updated. However, most US images are kept current. Google announces imagery updates on their LatLong Blog[53] in form of a quiz, with hints of the updated locations. The answers are posted some days later in the same blog.
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