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Making use of the Google Earth API

mar 05-07-2016

Although the Google Earth API was officially deprecated back in December 2014, Google chose not to shut it down on schedule in December 2015 and have instead kept it running. Although you should not design websites around it as most browsers no-longer support the technology it is based on (NPAPI), it can still be a very useful tool for particular purposes.

Today we are sharing a tool based on the Google Earth API that we developed for our own purposes, but think others might find useful. If you have a collection of placemarks and want to know whether or not Google Earth has relevant imagery, rather than switching to ‘historical imagery’ then checking them one by one in Google Earth, this tool can do much of the work for you.

As an example of what it might be useful for, we took this page on Wikipedia that lists the locations of all the tornados in the United States from January to March 2016. We used the provided coordinates to create placemarks in Google Earth. We then used the tool to generate a new KML which shows which placemarks have imagery from 2016.

Placemarks with imagery from 2016 are highlighted in green.

It is not perfect in this particular situation as it does not tell us whether the imagery in question was captured before or after the particular tornado. To achieve that, we would have to find a way to include the tornado date in the original KML file. But it does considerably cut down on the number of placemarks we should check if we want to find signs of tornado damage. You can get the above KML file here. Keep in mind that many of the tornados were very week and did almost no damage.

In order to use this tool, you need to open this page in Firefox which, as of this writing, still supports the Google Earth API. The first time you open the page, you must click the link that says ‘Activate Google Earth’, then choose ‘Allow and Remember’ in the popup. Then refresh the page.

Next, select the KML file containing the placemarks you want to use, and enter a date in the space provided and click “Get Dates”. The tool will check the latest imagery date for each location and when complete will download a KML file which you can view in Google Earth. Note that each placemark takes two seconds because we find that the Google Earth API is a bit unreliable if rushed. The resulting KML file includes all placemarks from the original file and puts the date of the most recent imagery in the placemark description. In addition, it colour-codes the placemarks yellow and green depending on whether or not the latest imagery is before or after the date provided below.


KML file:

Date: (yyyy/mm/dd)

Get Dates

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Catégories: Sites Anglophones

Google Earth weather layer broken again

lun 04-07-2016

Over the last few weeks we have had several emails from GEB readers saying that the weather information in Google Earth is not accurate. We have compared the temperatures shown in Google Earth with those shown on, which is listed as the source of the information in the Google Earth popups, and we have found that the figures do not match and in some cases there are significant differences. Last year the weather layers had a similar problem, with the weather data simply not being updated. In that case it was obvious that the issue was a communication problem between Google Earth and the source of the information, as the dates shown in the popups were not being updated, indicating that the data was old. This time, however, the dates shown in the popups are current, but the actual figures are not changing. We checked some locations and although the date shown changes quite regularly the figures displayed in the popups do not. Only the ‘conditions and forecast’ layer is affected as far as we can tell. We verified by comparisons to various websites that the cloud and radar maps are reasonably current.

Despite the name, Snowville, Utah, is actually quite hot this time of year, yet Google Earth gives it 37°F / 3°C. gives its temperatures in the 55°F – 90°F range, so the issue is not one of time of day.

We checked locations on several different continents and the issue seems to be universal.

The post Google Earth weather layer broken again appeared first on Google Earth Blog.

Catégories: Sites Anglophones

Animating the Aral Sea

ven 01-07-2016

Earlier this week Google released an update to the global mosaic that Google Earth shows when zoomed out. In our post where we were having a deeper look at the mosaic, we mentioned that it would be interesting to try and put a date on the imagery by looking at inland lakes or seas that are known to be growing or shrinking over time. So, we decided to have a go at doing this.

We chose what is possibly the largest and best known example of this – the Aral Sea. According to Wikipedia it is technically a lake and the ‘Sea’ in the name is a reference to the sea of islands that used to inhabit it. Formerly one of the four largest lakes in the world, it had shrunk to just 10% of its former size by 2007. So, it seemed like an excellent candidate for our project.

We had a look through historical imagery, and clearly we were not the first to think of this, as Google has kindly provided historical images of just this location starting in 1973. Below, you can see an animation made with Google Earth historical imagery and the final frame is the new global mosaic.

Speed in milliseconds per image:

Next, we had a look at Google Earth Engine’s ‘timelapse’ feature. Just go to this site, move the map to the location of the Aral Sea and start the animation. Again, it looked fairly encouraging, except for the fact that it seemed to experience a regrowth in 2010. Google Earth Engine’s timelapse feature is made in a similar way to the method used for creating the global mosaic. Many Landsat images from a particular year are combined to create an image that is as cloud free as possible. The difference with the global mosaic is that there is no need to restrict the search for cloud free imagery to a single year. Earth Engine’s ‘timelapse’ feature currently ends in 2012 – which is when Google first released a global mosaic for Google Earth. Let’s hope that with this new global mosaic, they will consider updating the ‘timelapse’ feature too.

So, the next step was to download Landsat imagery of the region for more recent dates. We stuck to Landsat 8 imagery, which begins in 2013. We also selected only images with less than 50% cloud cover. The result can be seen in the YouTube video below:

As you can see above, the Aral Sea is not consistently shrinking over time, but varies quite considerably over time. Whether this was also the case in previous years, we don’t know, as the Google Earth Engine timelapse only does one image per year and that image is a compound image from multiple images from the year. Clearly the Aral Sea has shrunk considerably and is still, on average, shrinking, but it is not so easy to judge the exact time the imagery in the global mosaic was captured. Compounding this is the fact that there is ice on the shores in the winter months, which changes the appearance of the shoreline. However, by carefully looking at the south western branch of the lake, which appears to be shrinking fairly consistently, we believe the Google Earth global mosaic of that part, most closely matches the size of the lake in early 2015. But, the area as a whole is a compound of multiple images and we are fairly sure we can even detect Landsat 7 stripes in the central region between the two lakes. Keep in mind that the Landsat 7 satellite is still operating, so this does not mean that the imagery used is old.

Finally, below is an animation combining both Google Earth historical imagery and the Landsat imagery. We are not sharing the Landsat imagery as a download because it is rather large (90Mb).

In the above video, the dates shown in the timeline are only approximate for the Landsat images, as there were often no corresponding historical imagery dates to match. The correct dates for the Landsat imagery are shown in the first video.


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Catégories: Sites Anglophones

The best of Google Earth for June 2016

jeu 30-06-2016

The biggest news this month is that Google Earth got a makeover, with Google updating the global mosaic shown when zoomed out. Overall, we like it a lot, but nothing is perfect, so we had a look at some of the minor issues it still has.

There were several imagery updates in the month and we had a look at some of the interesting sights to be found in the imagery, including:

We also discovered an image in the Sahara Desert from Google’s Terra Bella. The image has since been removed. Presumably Google were just testing something. It would be nice if they do decide to use Terra Bella imagery to fill in the gaps in Google Earth’s high resolution imagery.

We had a look at a new tool by GeoSage called Spectral Transformer for Sentinel-2 Imagery which, as the name suggests, is for processing imagery from the Sentinel program.

We noted that Google had released some imagery of Rio de Janeiro, Brazil, that was captured in 2013 and we talked about the reasons why it sometimes takes Google so long to release 3D imagery.

We had a look at an archaeological find in Petra, Jordan, that was found by Dr. Sarah Parcak with the aid of satellite imagery.

We had a look at a story about a Kraken being spotted in Google Earth imagery – which turned out to be a rock.

We had a look at how to make desktop backgrounds with Google Earth imagery (Google Earth Pro makes it easy).

We came across a story on Bellingcat that mentioned that Google is continuing to update historical imagery in Ukraine, despite it being essentially censored since July 2015. We discussed the issue as well as having a look at some of the locations relevant to the Bellingcat story.

We had a look at Sun-synchronous orbit, the orbit configuration used by most imaging satellites.

We provided a Google Earth API based tool for making historical imagery animations and also gave some tips for making good animations.

We had a look around Rio de Janeiro and the developments in preparation for the upcoming Olympics. We also had a look at an oil refinery there and animated the oil tanks showing the floating roofs rising and falling over time, depending on oil stocks.

The post The best of Google Earth for June 2016 appeared first on Google Earth Blog.

Catégories: Sites Anglophones

The Google Earth new global mosaic: a deeper look

mer 29-06-2016

Google recently refreshed Google Earth’s global mosaic with newer, sharper imagery. So far, we like it very much and think it is definitely an improvement. However, we will have a look around and see if we can find any flaws or interesting aspects to the new imagery.

Landsat 7 stripes

We already pointed out yesterday that although Landsat 8 imagery was used in the new mosaic, it is not entirely free of Landsat 7 imagery with its characteristic stripes. They typically show up in hard to photograph places, such as those that have near year round snow cover or cloud cover, but we think we even saw some in the Sahara.


There are a few locations where non-Landsat imagery has been included in the mosaic. This includes a number of islands, such as Svalbard and the islands in the South China Sea.
Below we can see a particularly noticeable strip across Smith Island, which is part of the Andaman and Nicobar Islands in the Indian Ocean. The image is actually a DigitalGlobe image from 2011 which disappears as you zoom in.

We believe the reason for this is that there simply aren’t any good quality, snow-free and cloud-free Landsat images of the locations in question. Islands, it would appear, are cloud magnets.


Overall, the contrast in the imagery is noticeably higher and features you may have never noticed before stand out. Lakes generally seem to be greener or browner than before.


It is important to note that the ocean floors are actually a different data set and have not, as far as we know, been updated at this time. However, they did receive a significant update in January this year. We have come across some oddities in the margin between land and sea. For example, along the coast of Vietnam there is a thin border of brown where the Landsat mosaic ends, but between that and the sea floor data is some other imagery which includes some clouds.

We saw this same effect in a number of other locations around the world.

We also found that if you zoom in on Chandler Sound, which is part of the Mississippi delta in the Gulf of Mexico, Google Earth shows this strange pattern:

We are not sure if this has anything to do with the global mosaic update.

Dating the imagery

The imagery is a mosaic collected from parts of images from the Landsat archive going back many years, so it is impossible to put a date on the whole mosaic. However, there are specific places where it is possible to determine the approximate date of the imagery used. The best locations to do this would be large lakes or inland seas that are shrinking or growing over time. We haven’t yet done this for any such lakes, but we did check the Nansen Ice-shelf in Antarctica and determined that the imagery there has not been changed from the previous mosaic. The imagery is from 2003 as we determined when watching the ice sheet crack. We also checked Bento Rodrigues in Brazil and are fairly sure that the imagery is from before the disaster that took place there in December last year


Landsat imagery has a resolution of only about 30m per pixel and we suggested yesterday that Google consider using Sentinel imagery, which is higher resolution. However, after some consideration we have realised that for the global mosaic, the important factors are consistent colouring and good global coverage. As you zoom in, Google Earth transitions to higher resolution imagery where available so greater resolution of the global mosaic is not necessary. It is, however, the case that there are some parts of the world where no higher resolution imagery exists and the Landsat imagery is used even when you zoom in and only for these locations does Google need to seek alternative sources. For much of the globe they have already used medium resolution imagery from Spot Image. For more on what image sets are used where, see our series on Google Maps API Maximum Zoom.

To see the locations featured in this post in Google Earth download this KML file.

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Catégories: Sites Anglophones

Google Earth gets a makeover!

mar 28-06-2016

Google Earth has just had a makeover. Google has refreshed the global mosaic imagery that you see when zoomed out with newer, better quality imagery. When you zoom in, Google Earth transitions to higher resolution imagery where available, but in places where it is not available, the global mosaic remains. When Google Earth was first released it looked like a patchwork of imagery – essentially the same as it does today when you switch to ‘historical imagery’. Then, in 2012, they released ‘Pretty Earth’ a global mosaic derived from Landsat data which made Google Earth look a lot better. As far as we know, this is the first refresh to the global mosaic since then. The first mosaic was produced using Landsat 7 data. Landsat 7 has faulty instrumentation, which resulted in stripes in the imagery at some locations.

Read more about the new global mosaic on Google’s Lat Long Blog.

Landsat 8 was launched in 2013 and the new mosaic incorporates imagery it has gathered. However, we believe we can still detect, in places, the characteristic stripes of Landsat 7 data, suggesting that the mosaic is not exclusively from Landsat 8.

A location in Venezuela. The squares are roads. The broader, nearly horizontal stripes in the vegetation are almost certainly due to a Landsat 7 image being used.

Also see the Vatnajökull Glacier on Iceland for another location where the Landsat stripes are visible.

Overall, the contrast is higher in the new mosaic and in parts of the US you can see a distinct checkerboard pattern:

The checkerboard pattern is real, being a consequence of the Jefferson Grid.

The mosaic is created by carefully selecting cloud-free and snow-free sections of imagery from the catalogue of Landsat imagery. The resulting, largely cloud-free and snow-free view of the world is actually quite unrealistic. In some cases, such as some mountain ranges and the poles, it has proved impossible to find completely cloud-free, snow-free imagery.

Some clouds are visible in the Falklands.

The northern coast of Greenland hasn’t fared too well with the update, but that is because this is outside of Landsat’s coverage.

Overall, we think the new mosaic is a significant improvement, but without the old one to compare it with, it is difficult to make an accurate comparison.

As far as we know, Sentinel imagery is freely available under similar conditions to the Landsat data. In addition, it is higher resolution than Landsat data. We wonder whether Google has looked into incorporating Sentinel data in the global mosaic.

To find the locations mentioned in this post in Google Earth download this KML file.

The post Google Earth gets a makeover! appeared first on Google Earth Blog.

Catégories: Sites Anglophones

Historical imagery and Ukraine

lun 27-06-2016

As we have mentioned in the past Google Earth does not have any imagery of Ukraine since June 2015, which puts it on the list of censored countries that includes Afghanistan, Iraq and Syria. However, a recent report on the citizen journalism site Bellingcat states that Google recently added some historical imagery from July 17, 2014, the day of the downing of Flight MH17. In fact they even know the exact time the image was captured: 11:08am (local time). Google Earth does not show the time that imagery was captured but the reporters at Bellingcat know exactly which DigitalGlobe image was used, and DigitalGlobe does know the exact time that a given image was captured.

If they are correct that the image was only recently added to Google Earth, this would suggest that whatever mechanism has been used to censor the country does not extend to historical imagery from 2014. Also of note is the fact that the Ukraine received Street View in October 2015 although it doesn’t appear to have been updated since then. The most recent Street View we could find was dated July 2015. There is no Street View in most of the eastern parts of the country and Crimea. There is some Street View of Donetsk, but that is dated 2011.

As you can see below, the new sighting of the BUK that is believed to have been used to shoot down Flight MH17 isn’t very significant, as it just adds an extra point to the fairly well documented route of the vehicle that day as identified by Bellingcat from various sources.

The green pin shows the new sighting.

To see the above locations in Google Earth download this KML file Note that the truck carrying the BUK can not be seen in the imagery in most of the locations marked, but rather it is known to have been at those locations at those times because of various photos / videos of it. See this Bellingcat report for the sources of the locations.

At one point Russia released a fake photo supposedly showing a fighter jet shooting down flight MH17.

The post Historical imagery and Ukraine appeared first on Google Earth Blog.

Catégories: Sites Anglophones

Bomb damage from the war in Yemen

ven 24-06-2016

There is an ongoing war in Yemen that started early last year. We have in the past had a look at the bomb damage at Sana’a airport in May 2015, and had another look in January this year.

Today we are having a look at some of the signs of bomb damage we have come across in other parts of the country.

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Destroyed building at the airport at Al Hudaydah, Yemen.

A damaged football stadium in Aden, Yemen.

Destroyed buildings at Ta’izz International Airport, Yemen.

Planes and a building destroyed at the airport in Aden, Yemen.

Speed in milliseconds per image:

Destroyed buildings near Ta’izz, Yemen.

Speed in milliseconds per image:

To find the above locations and a few more in Google Earth, download this KML file.


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Catégories: Sites Anglophones

What does it take to process 3D imagery?

jeu 23-06-2016

Google has recently been pushing out 3D imagery of various Brazilian cities in preparation for the Olympics. The interesting part, however, is that the imagery isn’t new. The imagery of Rio de Janeiro, for example was captured around February 2013 in preparation for the FIFA World Cup that took place in Brazil in 2014. At the time, Google did release some 3D imagery of Brazil, sometimes limited to the football stadiums involved in the world cup and small areas around them.

Google Earth does not provide dates for when 3D imagery was captured, so it must be compared with available historical imagery to determine the approximate date. The easiest way to do this is to look for a construction area. Depending on the availability of historical imagery the date can be determined within a month in some cases but only to within a couple of years in others.

Here are the dates that some of the 3D imagery, released in the last few weeks, was actually captured:
Rio de Janeiro – circa February 2013
Belo Horizonte, Brazil – August 2014
Manaus, Brazil – circa August 2015
Durban, South Africa – August 2015
Soweto, South Africa, between September 2015 and March 2016
Arecibo, Puerto Rico – after January 2016
Valencia, Spain – between July 2014 and August 2015
Daytona Beach, Florida – between January 2014 and February 2016

All this points to Google still having to do quite a lot of manual work when it comes to processing and releasing 3D imagery and they have a team that can only process a given amount in a given time. This is also borne out by the relatively regular release of 3D imagery.

So how much work do they need to do? There was the case of Lexington, Kentucky that we looked at, where several buildings were missing in the 3D imagery (it has now been corrected). If someone had to manually check every building in Rio de Janeiro, it could take years!

Let’s take a look around Valencia, Spain and see if we can identify signs of manual intervention in the 3D imagery generation:

If you don’t have it already, download our KML map of 3D areas to find out where new imagery has been released as well as the extent of existing imagery.

The post What does it take to process 3D imagery? appeared first on Google Earth Blog.

Catégories: Sites Anglophones

The rock near Deception Island that looks like a Kraken

mer 22-06-2016

A story about a Kraken (a legendary sea monster) being spotted in Google Earth imagery recently went viral. It turns out, however, that it is actually just a rock. The rock in question is named Sail Rock and lies south west of Deception Island, one of the South Shetland Islands near Antarctica. For more details of the story and a photo of the rock see this article.

Sail Rock, as seen in Google Earth.

It is not a new image, having been captured in 2013. We have actually been asked about this particular image in the past by a GEB reader and dismissed it as almost certainly a rock. Whenever you encounter unusual imagery and want to learn more about the area, try turning on various Google Earth layers to see if there are any relevant placemarks. The layers we find most useful for this are “Places”, “Photos” and “More->Wikipedia”. In this case there is actually a Wikipedia page for Sail Rock which has been updated with a reference to the recent story, but the page itself has been in existence since 2010. The placemark is a little to the north of the correct location, but close enough that you would find it if you were looking. In addition, always check ‘historical imagery’. In this particular case there are no other images of the location.

One clue that the image is of a rock is that Google Earth, in default view, shows satellite imagery in the vicinity and not ocean floor data. This indicates that Google considers the area to be land or close to land, i.e., they are aware of an island, rock or reef at the location.

And for final confirmation, since our trial licence for GeoSage’s Spectral Transformer has not yet expired, we decided to have a look at the location using Sentinel Imagery.

Copernicus Sentinel data, captured on March 28th, 2016.

Apparently the Kraken hasn’t moved since 2013. It is not a high resolution image, but it’s enough to confirm that there is definitely something unmoving at the location. To find the location and see the Sentinel image in Google Earth download this KML file.

For the history of nearby Deception Island see this YouTube video.

The post The rock near Deception Island that looks like a Kraken appeared first on Google Earth Blog.

Catégories: Sites Anglophones

Cylcone Roanu: Landslide and Floods

mar 21-06-2016

Cyclone Roanu was, according to Wikipedia, a relatively weak tropical cyclone that, nevertheless, caused severe flooding in Sri Lanka and Bangladesh. In addition, it caused a number of large landslides in Sri Lanka. The only imagery of the event so far in Google Earth is two patches of imagery of Sri Lanka: an image of the capital, Colombo, showing flooding and a set of images further inland showing a landslide.

The images were captured soon after the cyclone so they are rather cloudy and the light is poor.

Flooding in Colombo

Flooding in Colombo.

Much of the landslide is covered in cloud.

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Before and after of the tail end of the landslide.

To find the locations shown above in Google Earth, download this KML file.

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Catégories: Sites Anglophones

Google Earth Imagery Update: The Dallas, Texas Tornados

lun 20-06-2016

Google has recently pushed out another imagery update. Below we show approximate maps of where the new imagery from April, May and June can be found. There is almost certainly older imagery too, but it is harder to find.

June imagery.

May imagery. Red: Recently added imagery. Blue: Imagery as of June 12th.

April imagery. Red: Recently added imagery. Blue: Imagery as of June 12th.

To find the locations in Google Earth download this KML file.

As you can see above the new April imagery is almost exclusively aerial imagery, mostly of the US and a bit of Japan. Clearly aerial imagery takes a bit longer to process than satellite imagery. Strangely we have not yet seen any aerial imagery of Europe this year and very little satellite imagery.
[Correction: There are a few small patches of aerial imagery. ]

On December 26, 2015, there was an outbreak of at least 32 tornados, many of which were in the Dallas, Texas area. There is now some aerial imagery captured on April 28th, 2016, five months after the disaster. Nevertheless, the destruction is still very much in evidence, with the tornado scar over the Garland/Rowlett area visible from quite a high altitude. We have identified the tracks of the three strongest tornados.

We have in the past looked at low resolution imagery of the Garland/Rowlett area using both Landsat imagery and Sentinel imagery, but although we could clearly see the tornado scar, we could not see damage to individual houses.

Below are some ‘before and after’ comparisons. Drag the dividers left and right to compare the imagery.

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The above are all from the Garland/Rowlett tornadowhich was the strongest, but we show only a tiny fraction of the damage caused. Be sure to check out the imagery in Google Earth with this KML file as a guide. There is quite a lot of new construction in the area so when looking for damage be sure to compare with historical imagery as a house under construction looks remarkably similar to a severely damaged house.

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Catégories: Sites Anglophones

Making desktop backgrounds with Google Earth

ven 17-06-2016

When browsing some of the latest imagery in the recent imagery update we came across some beautiful images of islands of the Tonga archipelago in the South Pacific Ocean and we thought of using them as desktop backgrounds. This is also how we found the image of Hunga Tonga and Hunga Ha’apai for yesterday’s post.

The standard version of Google Earth only allows you to save or print images of what is seen on screen. Although it is possible to make Google Earth run full screen (F11) and can hide almost all the menus, it isn’t really satisfactory for capturing a full screen-resolution image. However, Google Earth Pro is free and allows you to save images up to a resolution of 4800 x 2866. Just go to File->Save->Save Image or look for the ‘Save Image’ button on the tool bar. It brings up a small tool bar where you can specify the resolution and other options. For a desktop background you probably want to turn off all the extras (title, legend, compass etc).

Note that this will not result in imagery of higher resolution than what can be seen in Google Earth.

Here are a few backgrounds we created for ourselves, but we highly recommend having a look at various tropical islands around the world to find your own favourite locations.

High resolution versions: 1920×1080, 3840×2160

High resolution versions: 1920×1080, 3840×2160

High resolution versions: 1920×1080, 3840×2160

If you love satellite imagery then we certainly recommend Google’s ‘Earth View’ Chrome extension. It also allows you to easily save any image you like as a desktop background (see the extensions menu at the top left). You can also get a similar extension by Planet Labs featuring their imagery.

The post Making desktop backgrounds with Google Earth appeared first on Google Earth Blog.

Catégories: Sites Anglophones

Two become one, Hunga Tonga and Hunga Ha’apai

jeu 16-06-2016

The recent Google Earth imagery update includes an image of a new island formed from Hunga Tonga and Hunga Ha’apai, part of the Tonga archipelago in the South Pacific Ocean. Hunga Tonga and Hunga Ha’apai used to be two islands with a submarine volcano between them. Then, in December 2014, the volcano started erupting and by mid-January 2015 a new island had formed with the volcano’s crater in the centre. See Wikipedia for more details.

Hunga Tonga and Hunga Ha’apai in 2014, before the 2014/2015 eruption

The new island, May 2016

See ground level photos here.

Another example of islands that have joined together through volcanic eruption that can be seen in Google Earth imagery is Nishinoshima, Japan.

Speed in milliseconds per image:

You can adjust the speed of the animation by dragging the slider.

Find the locations above in Google Earth with this KML file.


The post Two become one, Hunga Tonga and Hunga Ha’apai appeared first on Google Earth Blog.

Catégories: Sites Anglophones

Satellite image archaeology

mer 15-06-2016

We did a post on Dr. Sarah Parcak back in 2011. She is an archaeologist who frequently makes use of satellite imagery (including Google Earth) to make archaeological discoveries. She has written a book on the subject and even won the $1 million 2016 TED prize for her TED talk on the subject.

A recent story in the news is about a new find near Petra in Jordan that she helped discover, again through the use of satellite imagery. Read more about it here and here and more pictures here. Once the site was identified, archaeologists mapped the area in higher resolution using drones.

It was a little difficult to find the location in Google Earth as no coordinates are given. Although you can clearly make out the rectangular shape once you know where to look, it is not that easy to spot before you know where it is.

The newly identified structure as seen in Google Earth

To find it in Google Earth download this KML file. While you are there, be sure to check out the Street View of Petra. Google Earth doesn’t show the blue lines, but the Street View is there. The Street View was added in November last year.

The post Satellite image archaeology appeared first on Google Earth Blog.

Catégories: Sites Anglophones

Sun-synchronous orbit

mar 14-06-2016

In yesterday’s post we suggested that the reason for the near polar orbit of most imaging satellites was to improve coverage. After a bit more research it turns out to be more interesting than that. Apparently there is a special orbit called Sun-synchronous orbit, which is designed such that the satellite always crosses a given latitude on the ‘day’ side of the Earth at the same time of day. This has two benefits:

  • if two neighbouring images, or images of the same location are captured on consecutive passes of the satellite, they will have the same lighting (both the overall brightness as well as the length and direction of shadows), which makes it much easier to stitch them together in the case of side by side images or comparing for changes in the case of images of the same location.
  • the orbit can be positioned such that the satellite is always overhead as close to noon as possible (or whatever time is considered the best for imaging) for the latitudes of greatest interest. A non Sun-synchronous near polar orbit would result in some days when the satellite is orbiting in a plane at 90 degrees to the direction of the sun, which would make it constantly sunrise or sunset.

A Sun-synchronous orbit has a particular inclination depending on the altitude of the satellite. The lower the altitude, the closer the orbit is to the north-south direction. For a table of altitude vs. maximum latitude, and other technical details, see Wikipedia.

As far as we can tell almost all imaging satellites are in Sun-synchronous orbit, including SkySat-1 and SkySat-2. They also all have altitudes in the 500-900 km range, meaning they should all have similarly tilted orbits with a maximum latitude of around 82 degrees.

Thank you to GEB readers franksvalli2 and Vasilis for letting us know that the mystery image in yesterday’s post is almost certainly from one of the SkySat satellites. See this PDF file for details on those satellites, including their sensor arrangements which creates the distinctive ‘Y’ pattern. Also thank you to GEB reader Daniel Plant for bringing our attention to TeLEOS 1, which, as you can see here has a very different orbit.

We used our circle drawing tool to estimate the orbit of the satellite that took yesterday’s image and it came remarkably close to the expected 82 degree maximum latitude.

Although DigitalGlobe imagery in Google Earth is typically in both vertical and horizontal stripes, we believe that the imagery is actually captured by a satellite following a Sun-synchronous orbit very similar to the Sky-Sat orbits. We believe that the almost perfect north-south or east-west alignment of the DigitalGlobe strips is for some reason other than orbit. We have noted in the past that they line up with degrees of latitude and longitude.

For more interesting reading about orbits see this article from NASA.

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Catégories: Sites Anglophones

Google Earth Imagery Update: Strange image in the Sahara

lun 13-06-2016

Google has recently pushed out another imagery update. We created maps for March, April and May imagery, but did not find any significant changes in the March and April maps since the last update a week ago. There is, however, quite a lot of new May imagery.

May imagery. Red: Recently added imagery. Blue: imagery as of May 29th.

To find the locations in Google Earth download this KML file.

We haven’t been able to find any major events captured in the new imagery, but we did come across a strange image in the Sahara. It is in the south of Algeria and covers an area that has not previously been imaged with high resolution imagery.

We can see nothing of particular interest in the imagery, with half of the area being obscured by clouds, and no distinguishable features on the ground. Although it is hard to judge resolution, we think it is lower resolution than the nearby DigitalGlobe image. At first sight it appears to consist of three parallel strips, but the clouds all line up which would not be the case if it was three consecutive passes of a satellite, so we suspect it is all one image or three images captured in one pass. It also has no attribution (the NASA attribution is for the very low resolution background image).

Or first guess is a low altitude, relatively low resolution satellite, such as are used by Google’s own Terra Bella (formerly Skybox Imaging) and Planet Labs.

The strips are at a different angle from most satellite imagery which tends to be nearly aligned in a north-south direction. Strips of other alignments do exist but we believe they are typically for newly launched satellites that have not yet moved to a polar orbit. Near polar orbits tend to be preferred as it provides greater coverage. We do not know if this is the case for companies like Planet Labs which has large numbers of satellites.

If any of our readers know anything more about the origin of this imagery, please let us know in the comments.

Find it in Google Earth with this KML file.

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Catégories: Sites Anglophones

Spectral Transformer for Sentinel-2 Imagery

ven 10-06-2016

We have previously had a look at a tool by GeoSage for processing Landsat Data. At the time it was free for non-commercial use, but is no longer. It remains, however, the best tool we have come across for that purpose.

GeoSage has recently released Spectral Transformer for Sentinel-2 Imagery, a tool for processing Sentinel imagery. It is not free software, but well worth a look if you work with Sentinel Imagery. More of interest to us at GEB, is the wealth of information about Sentinel imagery and how to obtain it that they have provided on the product page.

The Sentinel program provides their own software called SNAP for processing Sentinel imagery, but we have not yet been able to figure out how to process imagery with it for use in Google Earth.

We downloaded the trial version of Spectral Transformer for Sentinel-2 Imagery and tried it out on some Sentinel imagery downloaded from Amazon Web Services. It was fairly straightforward to use and the resulting image can simply be drag-and-dropped into Google Earth Pro.

We tried it for the region around Katie, Oklahoma which experienced a number of tornadoes on May 9th, 2016. However, the only image available after that date was captured on May 25th and has excessive cloud cover. We tried false colour imagery using one infrared band (B08,B04,B03) but that was no better. So we thought we would try the shortwave infrared bands (SWIR), but that caused Spectral Transformer to crash on the final step, where it uses one of the 10m resolution colour bands to “Pan” sharpen the imagery (the SWIR bands are 20m resolution. So it looks like they still need to iron out a few bugs. However, the SWIR image at 20m resolution was created and could be viewed in Google Earth Pro.

[ Update: I tried running the same imagery combination the next day and it worked without crashing. I also got feedback from GeoSage suggesting it might be a RAM related issue (not enough free RAM). So if you encounter this problem try closing all other programs before running it to see if that helps (and possibly reboot first). If that does not work then contact GeoSage. ]

Try as we might, we just couldn’t see through the cloud cover. Copernicus Sentinel data, 2016.

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Catégories: Sites Anglophones

Tips for creating historical imagery animations

jeu 09-06-2016

This post is some tips for creating historical imagery animations using the ‘Historical Imagery Tour Maker’ we released in yesterday’s post.


The Google Earth plugin, like the default setting in Google Earth, tilts the view towards the horizontal as you zoom in close to the ground. In Google Earth you can stop that behaviour in “Tools -> Options -> Navigation -> Navigation”. For the plugin, there is no access to the settings, so, if you want your animation to be from directly overhead, be sure to press ‘u’ on your keyboard to reset the tilt after you have zoomed in to your area of interest. For a list of other Google Earth keyboard shortcuts see this website

Cache the imagery

If you do not have very fast internet, set the ‘step’ to several seconds and click ‘play’ and allow it to cycle through all the imagery in order to cache the imagery before you begin. In addition, when creating your final tour, you can create two versions, one with a long ‘step’ to be run first to pre-cache the imagery, then another to play it at the desired speed.

Maximum speed

If you use a step less than about 750 milliseconds, then Google Earth cannot keep up and will not show all the historical imagery when playing the tour. We are not sure whether this varies depending on your computer’s speed.

Recording Video

We have found that the built-in recording functionality (Tools->Movie Maker) of Google Earth Pro works rather well. However, it removes the historical imagery time bar and the status bar, so you cannot see the dates in the resulting footage. We used the highest quality settings and 10 frames per second. One nice feature of the Movie Maker is that it waits for imagery to load.

Before you start recording, make sure the tour is not set to auto repeat or the recording never stops.

Screen recording software can also be used. Use F11 to go full screen then hide the side bar and tool bar. We don’t know of a way to hide the menu.

Here are a couple of tours we have created:

Get the Google Earth tour here

Get the Google Earth tour here

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Catégories: Sites Anglophones

Advanced Historical Imagery Tour Maker with the Google Earth API

mer 08-06-2016

There are several different ways to automate animated historical imagery that we have explored in the past.

The first, and easiest, is to use a Google Earth Tour that simply changes the date by a given increment at a set frequency. So you could, for example, change the date by one month every second. In this post we presented some JavaScript to help with creating such tours. The main disadvantage of this technique is that Google Earth’s historical imagery is not regular and so you end up with periods of no imagery changes, and some skipped images. The technique does have the advantage of accurately representing the passage of time.

The second technique is to obtain the list of imagery dates using the Google Earth API and then use a tour to change the date, showing each existing image at a given frequency. This results in an animation that shows all the images in a given time range. We presented a tool for doing this in this post.

An outstanding problem that occurs with both techniques, is that Google Earth imagery is often not the best quality so you get an animation that includes some images with excessive cloud cover or updates that only cover part of the area of interest and do not look good. In addition, if you are trying to show change over time, you may not want images that are too close together in time if no significant differences can be seen between them. When we manually create animations for the blog we choose each image to include.

Some time ago we created a tool for creating Google Earth Tours that include or exclude images of your choice. We created it at the time the Google Earth API was expected to be shut down, so we chose not to share it. However, Google has so far kindly kept the Google Earth API alive, so we think people may find it useful.

It requires a browser that supports the Google Earth API, which, as far as we know is only Firefox. So, you will need to open this post in Firefox, and click ‘Activate Google Earth’ and then ‘Allow and Remember’ in the popup.


To begin, zoom in to the location where you want to create the animation. Then click ‘Get dates’. The tool will obtain the list of dates available for that location. Note that for locations with a large number of images, this may take a bit of time.

For most animations, you will want to start the animation at a specific point in time. Go to the date you wish to start at in the Google Earth plugin, then click ‘Set first date’. This will exclude all dates before this date.

Now go through each image deciding whether to include it in your animation or not. You can either select images with the plugin or use the ‘Next’ button to cycle through images. If you definitely want an image, click ‘Include date’, if you definitely do not want an image, click ‘Exclude date’. The tool has two modes. You can choose to select specific dates to include in your animation, or select specific dates to exclude. If you are only removing a few images, then the latter mode is easier.

Once you have gone through the imagery you can see how it will look by clicking the ‘Play’ button. If you are satisfied with the results, set speed of the animation by adjusting ‘Step’ which is the time between frames, then click ‘Download Tour’. You can now open the downloaded file in Google Earth and play the tour.

Get dates (warning! clears included and excluded lists)
Set first date
Play  Stop   loop.  Next  Step (milliseconds):
Include date Reset date Exclude date

Download Tour
Use ‘includes’ only
Use ‘includes’ and ‘dates available’

Included dates Dates available Excluded dates

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Catégories: Sites Anglophones