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How much historical imagery is there in Google Earth?

jeu 07-04-2016

This is the third post in a series looking at how much data is in Google Earth. We have already looked at how much data per unit area 3D imagery requires and how much data different types of 2D imagery require. Today we are looking at historical imagery.

Our first test was to pick a location that we know has a lot of historical imagery. We chose Rio de Janeiro, Brazil. We prepared the view we were interested in and cleared the Google Earth cache then allowed the default layer to load. Just the default layer, without moving the view at all, filled the cache to 4 MB. We then switched to historical imagery and cycled through all the historical imagery, again without moving the view. The cache was now at 580 MB. The reason for the enormous size is that Rio has approximately 220 unique images for the location we chose. On average, each image added about 2.6 MB to the cache. This is less than the default view takes, because many of the historical images do not cover the full area in the view, with some of them being only barely visible at the edge of the screen.


The area we chose in Rio de Janeiro, Brazil.

So how much historical imagery is there globally? We have tried to answer that question before with our historical imagery density map. Since then, we have created a higher resolution version, although it is not quite complete.

In the standard heat map, we used a logarithmic scale to help make the patterns in the historical imagery stand out. To get a better idea of just how much historical imagery there is overall, we have a simplified version shown below. It shows areas with 10 to 24 images in green, areas with 25 to 49 images in yellow and areas with 50 and over images in red. Most of the world has less than 10 images in a given location and in fact most of the oceans and much of the polar regions and deserts have no historical imagery whatsoever. There is also a bug in the way Google Earth shows historical imagery on the timeline that causes it to incorrectly report the number of images along coastlines or other regions that have no historical imagery, but are near to areas with a lot of historical imagery. This is what causes all the large patches around the edges of the continents in the screenshot below. This makes it impossible to directly do calculations on the data. However, by rough approximation we believe that historical imagery, if uniformly distributed, could cover the worlds land masses at least 5 times over.

To see the historical imagery density map in Google Earth download this KML file.

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Catégories: Sites Anglophones

NASA and Japan make ASTER imagery available for free

mer 06-04-2016

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of the instruments on NASA’s Terra satellite. Although it is a NASA satellite, the instrument belongs to Japan’s Ministry of Economy, Trade and Industry (METI). The instrument was launched in 1999 and has captured more than 2.95 million individual scenes since then. On the first of April this year NASA announced that the full catalogue of imagery is being made available to the public at no cost. The instrument, amongst other things, takes stereoscopic images that enables it to calculate altitudes albeit rather low resolution. The elevation data has always been available to the public at no cost.

The most interesting images have been collected in a gallery found here. You can also see some of the more interesting images in this article and this one.


Mt. Etna, when it erupted in July 2001. The full resolution image and description can be found here.


This image shows the 3D capabilities of ASTER. The full resolution image and description can be found here.

To access the full database of imagery, you can use the MADAS (METI AIST Data Archive System). A really nice feature is that it allows you to download the images as network-linked KML files.

The imagery has a similar resolution to Landsat imagery (approximately 30 m per pixel), so is really only suitable for viewing large scale phenomena. As with Landsat imagery its best use would be to see current events before other satellite imagery becomes available. In December last year we used Landsat imagery to look at the scar made by a tornado near Holly Springs, Mississippi. We found it relatively easy to find an ASTER image of the same region captured on March 28th, 2016, and the scar is still visible. Download this KML file to view it in Google Earth.


The image only covers a small part of the tornado’s track.

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Catégories: Sites Anglophones

How much data do different types of imagery need?

mar 05-04-2016

This is the second in a series of posts on Google Earth data sizes. Yesterday we had a look at 3D imagery and also compared it to the aerial imagery in the same location. Today we are looking a the different types of 2D imagery. As we have seen in the past, Google Earth has imagery in a wide variety of resolutions.


Just that tiny white square has 1.5 GB of aerial imagery.

We tested using regions of 100 square kilometres with a camera height of 1 km, except for the regions with aerial imagery, where we set the camera hight to 300 m to try and ensure the imagery loaded completely.

#countryTable td,#countryTable th { text-align: right } #countryTable th{padding-left:14px;} #countryTable td:first-child ,#countryTable th:first-child{ text-align: left;padding-left:0px; } #countryTable {font-size:10pt} Location Imagery type Size in MB Germany Aerial imagery – Geobasis-DE/BKG 1,532 United Kingdom Aerial imagery – Google 2,002 Japan Aerial imagery – Google 1,930 South Africa Satellite imagery – CNES / Astrum 247 Canada Satellite imagery – DigitalGlobe 368 Algeria Satellite imagery – Cnes / Spot Image 20 Papua New Guinea Satellite imagery – Landsat 16 Pacific Ocean near Hawaii Ocean floor detailed 12 South Atlantic Ocean Ocean floor minimal detail 8 Zoomed out view of Google Earth 3

As you can see, the amount of data used by different imagery types varies dramatically. The ocean floor figures may be a little inaccurate as they include the 3 MB or so that Google Earth downloads just on logging in to show the earth when zoomed out. We initially thought the German aerial imagery was higher resolution than in other parts of the world, but the results suggest that is not the case.

The country of Germany is approximately 350,000 square kilometres. It would take about 525 GB to store all the aerial imagery in the default view for the whole country. Historical imagery adds a whole new dimension, which we will look at in our next post in the series.


Samples from the locations we tested. Note the scale on each image.

To see the locations we tested with in Google Earth, download this KML file.

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Catégories: Sites Anglophones

How much data is in Google Earth’s 3D imagery?

lun 04-04-2016

Google continues to add new 3D imagery on a regular basis. Most of the major population centres in the US and Europe will soon be covered and many other parts of the world have significant areas covered too. So, just how much data does it constitute and how does it compare to plain overhead imagery? And when you browse an area in Google Earth, how much data must your computer download?

To answer the above questions we used the Google Earth cache to monitor how much data is being downloaded. We first deleted the entire cache, which can be done by first signing out of the Google Earth servers (File->Server Sign Out) and then going to Tools->Options->Cache and clicking the ‘Delete cache file’ button. Next, we created a zigzag path that covered a square region of 3D imagery and ran it as a tour as described in this post. We initially set the camera height for the tour to 1 km. At this height the camera can see the next row of the zigzag so that as it proceeds, all imagery in the area covered is fully loaded to the resolution Google Earth chooses for that view height. We did this for several different patches of 3D imagery. We also discovered after running most of our tests that if we get closer, then even higher resolution imagery is loaded, so we did another test for a smaller area from a height of just 300 m.

Our main tests covered an area of approximately 100 square kilometres each. As you can see below, this is actually only a tiny amount in relation to some of the larger areas of 3D imagery, but we could not do much larger areas as we were concerned about exceeding the size limitations of the Google Earth cache. As it was, we discovered that although the maximum size you can set for the cache in Google Earth’s options is 2 GB we were, in fact, able to grow it much bigger. At one point it even exceeded 4.6 GB and then later shrunk to just over 2 GB.


The area we tested near Milan, Italy (white zigzag). The red outlines show areas with 3D imagery.


The zigzag shape we used. (This one is Tokyo, Japan).


A corner of the area covered showing that only the area around the zigzag was fully loaded.

We also ran each test with 3D buildings turned on, and 3D buildings turned off.

Here are the results for 100 square kilometres with a camera height of 1 km.

#countryTable td,#countryTable th { text-align: right } #countryTable th{padding-left:14px;} #countryTable td:first-child ,#countryTable th:first-child{ text-align: left;padding-left:0px; } #countryTable {font-size:10pt} 3D buildings enabled 3D buildings disabled Milan, Italy 3,097 MB 294 MB Atlanta, Georgia 1,468 MB 296 MB Abilene, Texas 803 MB 250 MB Tokyo, Japan 1,317 MB 273 MB

The surprise is the wide variation from location to location. The area near Milan, Italy, uses four times as much data as the area near Abilene, Texas. The figures for plain imagery are much more consistent. All the areas tested have aerial imagery. In a later post we will have a look at whether or not there is a difference between aerial and satellite imagery.

The second surprise was just how much data 3D buildings require. We ran a test from a height of just 300 m over an area of just 20 square kilometres and it filled up 2,230 MB of cache, so the figures above are actually much smaller than if the best resolution imagery possible is loaded. The single area around Milan, Italy that has 3D imagery is approximately 2,500 square kilometres so it requires approximately 278 GB of data. That’s about the same as a small hard disk drive.

To see the zigzags we used in our tests, download this KML file, and to see what parts of the world have 3D imagery download our KML map.

This is the first in a series of posts trying to work out just how much data is in various aspects of Google Earth. If all goes according to plan, we should, at the end, be able to make wild guess at just how big the Google Earth database really is.

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Catégories: Sites Anglophones

Tesla and Lithium

ven 01-04-2016

Tesla has started taking orders for the Model 3, its first electric car targeted at the mass market rather than the luxury car market. It was unveiled at a special even in California last night, March 31st, 2016. Tesla’s cars run on lithium-ion batteries. To make enough batteries for their cars, Tesla is building what will be the world’s largest lithium-ion battery factory, Gigafactory 1.
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Tesla’s Gigafactory 1 under construction.

To make the batteries, they need large quantities of lithium. They are hoping to get a lot of it from a mine in Nevada, not far from Gigafactory 1. Read more about it here. They will, however, probably need lithium from all over the world.

Some lithium mines look pretty much like any other mine in Google Earth, but a number of the larger ones get the lithium from brine water pumped up from underground into large evaporation ponds. Evaporation ponds used for obtaining salt from seawater often turn red, as we have seen before but it seems lithium evaporation ponds tend to be turquoise, with occasionally some green.


Silver Peak, Nevada


Atacama salt flats, Chile


Atacama salt flats, Chile


Atacama salt flats, Chile


Lake Zabuye, China

To find the above locations in Google Earth, as well as a few other related locations, download this KML file.

While researching this story we came across an image in South America dated February 28th, 2015, which is not yet in ‘historical imagery’. This means that there has been at least one imagery update in Google Earth since the last one we reported. We will not be able to tell the extent of the update until the imagery is pushed into ‘historical imagery’.

jQuery(function(){jQuery('#gigafactory').beforeAfter({imagePath: '/js/utils/',showFullLinks : false});});

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Catégories: Sites Anglophones

The best of Google Earth for March 2016

jeu 31-03-2016

This month saw the fifth anniversary of the Great East Japan Earthquake and Tsunami. In memory of the disaster, Google released fresh Street View and aerial imagery. Some was captured soon after the disaster and some much more recently. Because the older aerial imagery would not be visible in the default layer, Google pushed the fresh imagery and other imagery from around the world that had been added earlier into historical imagery. This allowed us to create imagery update maps. This in turn gave us the opportunity to look at a few interesting places in the new imagery.

This month Sri Lanka got Street View. Although the blue outlines do not show in Google Earth, the Street View is available and there is a lot to explore. We also had a look at the Batcave in Street View and some Thailand Street View captured with the Trekker.
 
 
 

Thanks to a tip from GEB reader Jackson, we discovered that several buildings in Lexington, Kentucky have not been rendered correctly in Google’s 3D imagery.
 
 
 
 

The posts we most enjoyed writing this month involved creating animations. The first used Landsat imagery to watch an Antarctic ice sheet as it cracks. Then we had a look at the growth of artificial islands, first in the Persian Gulf region and then the rest of the world.
 
 

Google acquired satellite imaging company Skybox back in 2014 and this month renamed it to Terra Bella. The name change is intended to indicate a change of focus from just a satellite imaging company to pioneering the search for patterns of change in the physical world.
 
 

We had a look at fairy circles in Namibia and Australia and also found similar patterns in other parts of the world. Thank you to GEB reader for linking to this Google Earth Community post on the topic. It includes a KML that shows the extent of fairy circles in Namibia.
 
 

We had a look at the cluster of earthquakes in Oklahoma caused by pumping waste water from drilling operations into deep wells. As was noted in the comments by GEB reader David Newton the vast majority of these quakes were not big enough to cause damage.
 
 

We provided a few tips and tricks for Google Earth:
* We had a look at a technique for caching Google Earth imagery using Google Earth ‘line tour’ feature.
* We created a tool for reducing the size of KML files by reducing the precision of the latitudes and longitudes.
* We showed you how to create custom icons.
* We had a look at advanced techniques for formatting the print options in Google Earth Pro.
 

We showed you how our code for determining whether or not a point is inside a polygon works.
 
 
 
 

We discovered Street View portals to the Moon, Mars and Atlantis.

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

Catégories: Sites Anglophones

Street View Trekker visits Thailand

mer 30-03-2016

Thailand has had Street View as far back as 2012. This post on the Google LatLong Blog says that over 150 other places and national treasures have recently received Street View. However, many of the places listed have Street View dated 2014, and the first place mentioned, Sukhothai Historical Park, even has Street View from 2013. So either they have taken a really long time to process the imagery, or they have made a mistake somewhere. Nevertheless, Thailand has some really beautiful places and is well worth a visit.

Expect to see elephants, spikes and intricate carving.


Sukhothai Historical Park. Explore in Street View


Sanctuary of Truth. Explore in Street View


Ancient Siam. Explore in Street View

Be sure to see the LatLong Blog for more locations to explore

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Catégories: Sites Anglophones

The Oklahoma Earthquakes

mar 29-03-2016

Starting in 2009 the state of Oklahoma has seen a dramatic increase in seismic activity. According to Wikipedia, it has gone from an average of less than two 3.0+ Mw earthquakes per year to hundreds in 2014 and 2015. This has been caused by increased drilling for oil and the subsequent pumping of waste water into disposal wells deep underground. Read more here. As a result of the increased seismic activity, the U.S. Geological Survey (USGS) has released a new ‘damage map’ showing the risk of damage due to earthquakes significantly increased for the region. Read more about it here and find the map here.

Google Earth has a built in ‘Earthquakes’ layer found in the ‘Gallery’ layer. It only shows earthquakes over 3.0 Mw and as you zoom out it filters out the smaller ones. The result is that when looking at the whole of the continental U.S., Oklahoma doesn’t stand out as being particularly unusual.

However, the ‘Earthquakes’ layer is provided by the USGS and it is possible to obtain more detailed layers directly from them. Go here for automatic live feeds that show recent earthquakes, or here for more advanced queries.

If we choose the “Past 30 Days, M2.5+ Earthquakes” and “Colored by age”, the cluster in Oklahoma immediately becomes apparent:

We can also use the more advanced queries to compare 2008 and 2015:


Earthquakes 2.5+ Mw during 2008.


Earthquakes 2.5+ Mw during 2015.

To see the above in Google Earth download this KML file. The 2008 and 2015 datasets only cover the region around Oklahoma as the USGS website has a limit on the number of quakes allowed in a single query.

The post The Oklahoma Earthquakes appeared first on Google Earth Blog.

Catégories: Sites Anglophones

The Batcave now visible in Street View

lun 28-03-2016

As revealed by Google Maps Mania, “Bruce Wayne’s residence” has been captured in Street View and it includes the Batcave. It is not true Street View, but what Google calls either ‘Business View’ or ‘See Inside’. As such, it does not show up as the normal blue lines used for Street View, but rather an unassuming orange dot by the side of the road near Orion Charter Township in Michigan, USA.

To explore it in Google Earth download this KML file then place the yellow man on the location it marks. Alternatively, go here to explore it in Google Maps.

Once you have entered Street View you find yourself in a small, unassuming country residence by a lake. Walk to the end of the room and you will suddenly find yourself in an underground tunnel that leads to the Batmobile.


The Batmobile in the underground lair.


A Batsuit in the making.

According to Wikipedia, a number of different buildings have been used to represent Wayne Manor. The only one we were able to get close to in Street View is Wollaton Hall, found in Nottingham, England.


Wollaton Hall, found in Nottingham, England.

For other movie-related Street View see:

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Catégories: Sites Anglophones

Watching artificial islands grow in Google Earth – Part 2

ven 25-03-2016

Yesterday we had a look at some artificial islands in the Persian Gulf region. Today we are looking at artificial islands in other parts of the world. We have chosen only islands that have been created or substantially modified within the time span of available Google Earth imagery (typically the last fifteen years or so).

Japan is mountainous and most of the available land on the coasts has been used. As a result, many of its airports are on artificial islands.

Haneda Airport, Japan, on an island itself, had an extra runway added that is on a new artificial island.

Kobe Airport, Japan.

Kitakyushu Airport, Japan.

Island City, Fukuoka, Japan. This is the only artificial island in Japan that we are featuring that is not an airport.

The Hong Kong–Zhuhai–Macau Bridge is, as its name suggests, a bridge connecting the three cities of Hong Kong, Zhuhai and Macau. The route consists of several long bridges and an undersea tunnel with artificial islands for the two entrances to the tunnel and a third island at the Zhuhai/Macau end of the bridge. As we have mentioned in the past, when satellite imagery extends into the oceans, Google Earth does not show it in high resolution. Sadly the Hong Kong end of the tunnel is, according to Google Earth, in the ocean and as a result the imagery showing it being constructed is out of focus.

The Zhuhai/Macau terminus.

The tunnel entrance in the Zhuhai/Macau direction.

The Maldives are a group of coral atolls in the Indian Ocean. Several of the atolls have been converted into more substantial islands.

Hulhumalé, Maldives.

Thilafushi (left) and Gulhi Falhu (right), Maldives.

We move on to Malaysia and its first man-made island – Marina Island.

Marina Island, Malaysia.

And finally we have Singapore, a small nation with a desperate need for more space.

Jurong Island, Singapore.

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

animateImages([{id:"HanedaAirport",qty:4},{id:"KobeAirport",qty:8},{id:"KitakyushuAirport",qty:4},{id:"IslandCity",qty:7},{id:"Zhuhai-Macau",qty:12},{id:"ZhuhaiMacauBridgeTunnelEntrance",qty:3},{id:"Hulhumale",qty:5},{id:"Thilafushi",qty:5},{id:"MarinaIsland",qty:6},{id:"Jurong",qty:7}]);

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Catégories: Sites Anglophones

Looking at the growth of artificial Islands in Google Earth

jeu 24-03-2016

There are quite a lot of artificial islands being built around the world. For example, last year we had a look at the islands that China is building in the Spratleys. Today we are looking at artificial islands in the Persian Gulf, where shallow seas and oil wealth create perfect conditions. In a later post we will have a look at artificial islands in other parts of the world.

We tried gif animations but the gif format has limited colours so we decided to create jpg animations with JavaScript. If they do not show correctly in your browser, please let us know in the comments.

We start with Bahrain, a small island nation that clearly feels the need to expand:

Amwaj Islands and Diyar Al Muharraq, Bahrain.

Durrat Al Bahrain, Bahrain.

Sitra, Bahrain.

Reef Island, Bahrain.

Next is the UAE, which is sprouting islands all along its coast:

The Palm Jebel Ali, Dubai.

Palm Jumeirah, Dubai.

The World, Dubai.

Then we have Qatar whose capital Doha is spreading into the ocean:

The Pearl, Qatar.

Lusail, Qatar.

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

animateImages([{id:"AmwajIslands",qty:5},{id:"DurratAlBahrain",qty:4},{id:"BahrainBay",qty:8},{id:"ThePalmJebelAli",qty:6},{id:"PalmJumeirah",qty:5},{id:"TheWorld",qty:6},{id:"ReefIsland",qty:12},{id:"ThePearl",qty:10},{id:"Lusail",qty:9}]);

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Catégories: Sites Anglophones

Sri Lanka gets Street View

mer 23-03-2016

Google has recently released Street View for the country of Sri Lanka. Read more about it on the Google LatLong blog.

As of this writing the blue outlines for the Sri Lankan Street View are not yet in Google Earth, but the outlines do show in Google Maps and Street View imagery is available in both products.

Sri Lanka is the world’s fourth largest producer of tea and much of the Street View shows vast tea plantations.


Mackwoods is a tea brand, and we believe that is tea growing on the hillsides. See it in Street View.


Most of the roads in Sri Lanka are very narrow. Although there are cars and buses, motorbikes and especially auto rickshaws seem to be a very popular form of transportation. See it in Street View


The locals seem pleased that they are finally getting Street View. See it in Street View.


A temple being repaired. See it in Street View.

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Catégories: Sites Anglophones

Caching Google Earth imagery with path tours

mar 22-03-2016

We have recently been catching up on the outlines for our KML of Google Earth 3D areas. The internet speeds here in Cape Town increase every year, but we still seem to spend a lot of time waiting for Google Earth imagery to load. When tracing out 3D areas, we have found it helpful to pre-cache an area before starting to draw and we thought we should share the technique, as our readers could find it useful in a variety of circumstances.


The border of the 3D imagery areas is often quite intricate.

The basic technique is very simple. Just draw a path where you wish to pre-cache imagery, then select the path and click the ‘Play Tour’ button that appears. Once the tour starts, go away and do something else for a while then come back when it is finished and you will find that imagery in the area you are interested in now loads much faster.


A ‘Play Tour’ button appears in the divider between Places and Layers whenever you select a path.

The default settings have the Google Earth ‘Camera’ follow the line quite closely and thus only imagery very near the line is cached. In addition, depending on the speed of your internet connection, the camera may move a bit too fast to fully cache the imagery before moving on. However, this can be adjusted with the settings found in Tools->Options->Touring:

We like to set the Camera Tilt Angle to zero (looking straight down) and the Camera Range to 1000 metres. Start the tour and see if the imagery is managing to load completely before it goes off screen. If not, reduce the Speed setting.

The above technique can also be used if you plan to use Google Earth offline, as you can pre-cache an area by drawing a zigzag path across it. Be sure to test it before setting off on a long journey.

To learn more about Google Earth’s cache see some of our previous posts on the topic.

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Catégories: Sites Anglophones

What’s that Image: Fire, Flood and Mud

lun 21-03-2016

Today we are having a look at some of the interesting imagery we have been able to find in the latest Google Earth imagery update.
.sliders img{ max-width:none; }

In November last year there were a number of bush fires in South Australia. The imagery below shows the burn marks of one of those fires.

Drag the divider left and right to see the before and after images of a fire in South Australia.

December last year saw major floods in South America, including Uruguay, Brazil, Paraguay and Argentina. One of the cities that were hit hard was Asunción, the capital of Paraguay. They had already experienced floods in July, 2015, which we have looked at before. Judging by the imagery available, the December flooding was worse.


Flooding in Asunción, Paraguay

Be sure to explore the imagery in Google Earth. By January 20th, 2016 the flood waters appeared to have subsided a little, but the area above was still flooded. There is a problem with the imagery for the area, with Google Earth sometimes switching to the January image as you zoom in, even if the time slider is set to a December date.

On November 5th, 2015, Bento Rodrigues, Brazil, was inundated in toxic sludge after a mine dam burst. We had a look at the imagery of the site in January. At the time we were able to follow the mud a little way downstream. More imagery further downstream has now been released, including some images of the mud entering the Atlantic Ocean.

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

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Catégories: Sites Anglophones

Watching Antarctic Ice Sheets Crack with Landsat Imagery

ven 18-03-2016

We recently came across this interesting story about an ice shelf in Antarctica which is slowly breaking off. The original story is on the NASA website here. The article features a couple of Landsat images captured in December 2013, and December 2015. However, Landsat imagery is freely available and relatively easy to obtain and put into Google Earth.

Our current favourite method for browsing Landsat imagery is with NASA’s Earth Explorer as it allows you to quickly browse through the imagery available and download low resolution versions, which can easily be put into Google Earth Pro.

In this particular case there is a surprising amount of imagery of the location in question. As we saw when we looked at the coverage that Landsat provides, the imagery is divided into rows and columns that cluster together towards the poles. This means that polar locations actually get covered by several adjacent columns and get imaged every couple of days or so. Most parts of the world only get imaged once every 16 days. However, the poles are also dark for about half the year so there will only be good images during the summer months.

In addition, many of the images have significant cloud cover, so we had to go through them and choose ones that showed a clear view of the location we were interested in. As you can see below we were able to obtain imagery all the way from January 2000 to March 2016. The latest image in the series was captured just last Saturday! (March 12th). There seems to be a bit of a gap in imagery around 2004/2005 but we did not investigate why.


Animation showing the ice crack moving and growing over the years. Larger version

You can see the ice flow like a very slow river. It moves approximately 3.8 km in the 16 year period shown above.

If you wish to explore the imagery in Google Earth you can download this KML file. We have had to crop the Landsat images considerably, showing only the location of interest in order to make the file a reasonable size.

The crack from the story has a precursor in 2000, which was as far back as we could go. However, it only lengthens and widens in 2013, when it starts to look like part of the ice shelf is breaking off.

The default imagery for the location in Google Earth is Landsat imagery from about January 2003.

The post Watching Antarctic Ice Sheets Crack with Landsat Imagery appeared first on Google Earth Blog.

Catégories: Sites Anglophones

Fairy circles

jeu 17-03-2016

In January we had a look at ant and termite colonies as seen from space. In that post we mentioned the phenomena of Fairy Circles from Namibia. Fairy Circles are regular patches of bare ground in the grasslands of Namibia as seen below


Fairy Circles in Namibia

A similar phenomenon has now been found in Australia. Read more about it here. This is what they look like in Google Earth:


Fairy Circles in Australia

There is Street View going through the area in Australia with Fairy Circles and you can see them along the sides of the road.

There has long been controversy over the origin of the Namibian Fairy circles, but the Australian scientists are fairly sure that the circles arise from feedback mechanisms related to plant growth and water run-off. They also predict that such patterns will arise in other parts of the globe with semi-arid conditions. So, we thought we would have a look and see if we could find any more examples.

The closest we have found so far are:


Somalia.


Burkina Faso.


Senegal.

The above patterns occur over vast areas. They are not quite the same as fairy circles and we could not find any ground level photos.

We also came across this interesting pattern in Australia:

Fairy Circles are patches of bare ground in grassland. This looks like patches of grass in bare ground.

To find all the above locations in Google Earth download this KML file. We have also included the locations from the ‘Ant Cities’ post as the patterns are remarkably similar.

The post Fairy circles appeared first on Google Earth Blog.

Catégories: Sites Anglophones

St. Patrick’s Day with Google Earth

mer 16-03-2016

Tomorrow, March 17th is St. Patrick’s Day. St. Patrick’s Day originated in Ireland but is now celebrated in many other parts of the world. The United States, for example, has major celebrations in many of its cities. Green is the traditional colour of St. Patrick’s Day and many places in the world ‘go green’ for the occasion. This includes adding dye to fountains or rivers, painting roads or road markings or lighting up buildings or even whole mountains with green lights. See some examples here. We had a look though imagery captured on St. Patrick’s Day, but were unable to find any imagery of celebrations.

Although we couldn’t find any St. Patrick’s Day imagery, we did find some imagery relating to St. Patrick. St. Patrick is the patron saint of engineers, and the Missouri University of Science & Technology has an organization called St. Pat’s board. We were able to find their logo in two places in Google Earth:

Some other St. Patrick’s Day imagery was found via GoogleSightseeing.


St Patrick’s Park in Indiana.


St. Patrick’s Cathedral, New York.


A Shamrock shaped maze near Dublin, Ireland.

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

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Catégories: Sites Anglophones

Making KML files smaller by reducing precision

mar 15-03-2016

Our KML map of 3D areas has been steadily growing in size as new areas are added. We have considered converting it to KMZ format, which is the compressed version of KML files. KMZ uses standard ZIP compression and in many cases provides significant compression ratios. In our case it would shrink our KML file by over 60%. We have held back because this would mean changing the link to the file and as most users access it via a network linked KML we would also have to notify them to re-download the original KML with a new link. There are workarounds to this problem, so it might be worth doing. The other downside is that it adds an extra step to the process of updating the file as we would have to convert it to a KMZ file before uploading it.

Because of the above complications we have been giving some thought to other methods of making the file smaller. One thing we have noticed is that Google Earth saves KML files with an unnecessary amount of precision for latitudes and longitudes. It typically saves latitudes and longitudes using 16 significant digits. If you configure Google Earth to use decimal degrees then edit a placemark in Google Earth, it only actually shows 5 decimal places.

So how many decimal places are actually needed? We calculated that rounding to five decimal places results in a maximum error of just under a metre. Rounding to six decimal places gives an error of less than 10 centimetres. 14 decimal places gives an accuracy of less than a nanometre. Given that most Google Earth data such as altitude data or even image alignment can be off by many metres, having nanometre resolution in your KMLs is just wasting space. For our KML file five decimal places should be more than enough.

As you can see below, the results were quite impressive. Simply discarding unnecessary decimal places reduces the file size by almost half. We also show the effects of using the KMZ format.

We thought that other people with large KML files might find the idea useful. So, below is a JavaScript tool that will take a KML file and reduce the precision of the latitudes and longitudes.

Notes:

  • The current version only reduces precision in placemarks, polygons and lines, it does not affect some other KML elements that include latitudes and longitudes.

  • To achieve the reduction of precision the code parses the KML and recreates it using our in-development KML library, so we can’t guarantee that it will properly handle unusual KML elements. If you use it, double-check that the resulting file still has everything in it that you require, and let us know in the comments if you encounter any bugs.

  • Unnecessary white-space is also removed which makes the file smaller but less human-readable.


input,select{padding:4px;color:black;border:none}input[type="file"]{width:350px;}

Precision: (decimal places)

 

Reduce precision

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Catégories: Sites Anglophones

Google Earth Imagery update – February 2016

lun 14-03-2016

Google has finally pushed the most recently published imagery into the historical imagery layer, so we can find and map out the imagery. We have been aware of new imagery being in the default layer ever since Super Bowl 50, when Google added an image of the stadium captured on 1st February. But other than a few images we came across by chance we did not know how extensive the update was. Even now, we can only map out imagery by date, which means we can be sure that all February imagery is new and we can tell roughly how much January imagery is new by comparing with the map we made in January, but we do not know how much older imagery has been added.


Imagery in Google Earth dated February 2016.


Imagery in Google Earth dated January 2016.

To find the imagery in Google Earth download this KML file. It has been created using the Google Earth plugin and the outlines are only approximate. To spot the actual imagery switch to historical imagery when looking at one of the regions highlighted then switch back and forth between the most recent image and previous images and you will be able to see which images are new.

Cyclone Winston struck the islands of Fiji in the Pacific on February 20th, 2016. There are several images in Google Earth captured a few days later. However, they are poor quality and we have not yet been able to identify any damage caused by the cyclone.

The most interesting imagery we have found so far in this update is actually not recent imagery at all. Google has added a large quantity of aerial imagery of Japan captured not long after the 2011 tsunami. The imagery was added together with some aerial imagery from February 2016 as we mentioned in this post last week on the fifth anniversary of the tsunami. However, the older imagery had not yet been pushed into ‘historical imagery’ at that time so it was inaccessible.

It is well worth having another look at the devastation caused by the tsunami as the new imagery is noticeably higher quality than what has been available until now.


The above image was captured several weeks after the tsunami. You can see an upturned boat (1) amongst the debris more than a kilometre inland. You can also see cleanup operations beginning (2).

For the location of the above image use this KML file, but we highly recommend exploring the whole north eastern coast of Japan. Switch to ‘historical imagery’ and look for the aerial imagery captured in April 2011.

Some of the imagery was incorrectly processed and streaks off into the ocean, resulting in what we see below:

The post Google Earth Imagery update – February 2016 appeared first on Google Earth Blog.

Catégories: Sites Anglophones

Custom Icons in Google Earth

ven 11-03-2016

When you create placemarks in Google Earth you can change the icon of the placemark by going to the placemark properties and clicking the icon button found just to the right of the placemark name. Google Earth then shows you a default set of icons you can use. However, it is also possible to use custom icons, which you can easily get from the web, or even create your own. Simply click the ‘Add Custom Icon…’ button and enter the URL of the icon you want or select ‘Browse’ to choose an icon you have created or saved to your local computer.

Also of interest is the option to set ‘No Icon’. This is very useful when you want to put plain text somewhere on the screen.

You can easily find a wide range of icons by searching on Google. The two best collections we know of are the icons provided by Google that are catalogued here and mapsmarker.com, which provides a variety of free icons specifically designed for maps.

There are a few things you need to be careful about when using custom icons. If you use an icon off the web using the URL and at a future date the website you linked to removes the icon, the icon will no-longer display properly in Google Earth. The icons from Google mentioned above should be pretty reliable, but if you get an icon from other sites and you are distributing your KML file, make a judgement as to how long those sites are likely to remain active and consider hosting the icons yourself or downloading them to include in the KML file.

If you use an icon from your local computer and you wish to distribute your placemarks in a KML file, make sure to save the placemarks in the KMZ format, as that will include the icons in the file. If you send someone the placemarks as a KML file, they will not have the icons and will see the red X that Google Earth uses when it cannot find an icon file.

If you add a custom icon it will remain in the list for the duration of the session, but if you exit Google Earth it resets the list to the default set and you have to add it again if you want to use it in new placemarks.

Google Earth’s default icon set has been updated in the past.

Below are some icons that we created for our own use. Feel free to download them to use in your own KML files. They work best if you do not give the placemark a name. If you want to include a name then create an extra placemark with no icon then you can adjust the position of the text. You can save the individual icons by simply right clicking on them and selecting ‘Save image as..’ (or the equivalent depending on your browser) or download the whole collection as a zip file here.


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Catégories: Sites Anglophones