My Google Map Blog

Cycle training

by sashafromdonetsk on Aug.25, 2016, under 3D Models, Argentina, Australia, Brazil, California, Denmark, England, Germany, Google Earth News, Google Earth Tips, Google Sky, Google maps, Hawaii, Indonesia, Ireland, Italy, Japan, Kenya, Mexico, Natural Landmarks, Netherlands, Sightseeing, Street Views, USA

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Improving our contour algorithm

by Timothy Whitehead on Aug.25, 2016, under 3D Models, Argentina, Australia, Brazil, California, Denmark, England, Germany, Google Earth News, Google Earth Tips, Google Sky, Google maps, Hawaii, Indonesia, Ireland, Italy, Japan, Kenya, Mexico, Natural Landmarks, Netherlands, Sightseeing, Street Views, USA

Last week we featured a tool for drawing contours which uses the Mapzen altitude API. We used a very simple algorithm called ‘Marching Squares’ that we found on Wikipedia. However, as GEB reader Боби Димитров pointed out in the comments, if you try to use too low a resolution altitude grid relative to the number of contours you want, you end up with something looking like abstract art:

The Marching Squares algorithm is remarkably simple. We just check every altitude from the grid obtained from the Mapzen API and colour it red or green based on whether it is above or below the altitude of the contour we wish to draw. Then we draw lines separating the two colours from the mid points of the rectangles in the grid as shown below:

However, we realised that if between a red and green dot rather than using the mid point, we check the altitudes of the points relative to our contour altitude and then use a point proportionally closer to the point closest to our contour altitude, we end up with a much better result:


All the settings were the same as the ‘abstract art’ sample above, except we use proportional ‘mid points’ on our squares.

And best of all, it only required changing one line of code!

We have also tried smoothing out the contours using this open source code. It generally works well, but it tends to result in some unwanted loops, so we probably need to look for a different curve algorithm.

Our next step will be to use a different technique to access the elevation data from Mapzen as suggested by them in the comments. If successful it should allow much faster access to the elevation data – and thus higher resolutions will be possible.

The changes so far have been added as options in last weeks post.

The post Improving our contour algorithm appeared first on Google Earth Blog.

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The Greenland hug

by StreetViewFun.com on Aug.25, 2016, under 3D Models, Argentina, Australia, Brazil, California, Denmark, England, Germany, Google Earth News, Google Earth Tips, Google Sky, Google maps, Hawaii, Indonesia, Ireland, Italy, Japan, Kenya, Mexico, Natural Landmarks, Netherlands, Sightseeing, Street Views, USA

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Hi Google

by wentworth on Aug.24, 2016, under 3D Models, Argentina, Australia, Brazil, California, Denmark, England, Germany, Google Earth News, Google Earth Tips, Google Sky, Google maps, Hawaii, Indonesia, Ireland, Italy, Japan, Kenya, Mexico, Natural Landmarks, Netherlands, Sightseeing, Street Views, USA

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4D Gondola in Google Earth

by Timothy Whitehead on Aug.24, 2016, under 3D Models, Argentina, Australia, Brazil, California, Denmark, England, Germany, Google Earth News, Google Earth Tips, Google Sky, Google maps, Hawaii, Indonesia, Ireland, Italy, Japan, Kenya, Mexico, Natural Landmarks, Netherlands, Sightseeing, Street Views, USA

Steven Ho, whose work we often cover has recently updated a Google Earth animation he first created back in 2007 showing the Maokong Gondola of Taipei. We covered his original 2007 version in this post.

Below is a YouTube video of the tour, but we highly recommend also trying out the KML tour, which you can download from Steven’s blog.

It is excellent work and shows off some of the capabilities of Google Earth tours. It also highlights a few of the limitations. For example, it is not possible to stop and look around without pausing the animation, so you can only really see the animation from the angles provided in the tour.

A lot of work clearly went into getting it all right. There are 147 cable cars all moving correctly along their cables, which follow a long twisting route. He also notes that he does some tricks with the satellite imagery, switching between the default view and ‘historical imagery’. He does this because the default view shows a more uniform view from high altitudes, but actually has quite old imagery when you zoom in. Google has kept imagery from 2006 in the default layer because it is better quality than more recent imagery. However, the Maokong Gondola was opened in 2007, so for the closeup section of the tour, Steven switches to the more current imagery (from February 2016) found in ‘historical imagery’.

The post 4D Gondola in Google Earth appeared first on Google Earth Blog.

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Done

by StreetViewFun.com on Aug.24, 2016, under 3D Models, Argentina, Australia, Brazil, California, Denmark, England, Germany, Google Earth News, Google Earth Tips, Google Sky, Google maps, Hawaii, Indonesia, Ireland, Italy, Japan, Kenya, Mexico, Natural Landmarks, Netherlands, Sightseeing, Street Views, USA

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Long cowl

by sashafromdonetsk on Aug.23, 2016, under 3D Models, Argentina, Australia, Brazil, California, Denmark, England, Germany, Google Earth News, Google Earth Tips, Google Sky, Google maps, Hawaii, Indonesia, Ireland, Italy, Japan, Kenya, Mexico, Natural Landmarks, Netherlands, Sightseeing, Street Views, USA

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Animating Landsat imagery in Google Earth

by Timothy Whitehead on Aug.23, 2016, under 3D Models, Argentina, Australia, Brazil, California, Denmark, England, Germany, Google Earth News, Google Earth Tips, Google Sky, Google maps, Hawaii, Indonesia, Ireland, Italy, Japan, Kenya, Mexico, Natural Landmarks, Netherlands, Sightseeing, Street Views, USA

Last week we created a KML file to easily preview the latest Landsat imagery. The data comes from Amazon Web Services (AWS), which hosts a large amount of Landsat 8 imagery and also includes some handy thumbnail images. So, we have now created a KML file that automatically creates animations from the thumbnail images.

Yesterday we had a look at the coverage of Landsat 8 imagery, but we focused on how recent the imagery is. Today’s KML file instead colour codes tiles based on how many images are available. As we noted yesterday, the AWS archive is Landsat 8 imagery only and does not include all the imagery. It turns out that most of the world includes a fairly comprehensive set of imagery from 2015 onward, whereas the US (excluding Alaska) has imagery going back to 2013. The result is that most locations outside the US have about 44 scenes whereas the US typically has nearly twice as many, at about 77 scenes. Note that these figures increase with time as the data is live and a new scene is added to each tile approximately every 16 days.

To see the animations, download this KML file. Click on any coloured tile for an animation of that location. Depending on your internet speed, it may take a short while to load all the images. If you have slow internet or just want to get a quick preview of the animation, then download this KML file which uses smaller, much lower resolution thumbnails.

There are three sliders. The first slider shows the progress of the animation and allows you to manually switch between images. Doing so stops the animation, which you can restart with a button. The second slider lets you adjust the speed of the animation. The third slider allows you to filter the images by removing any with over a specified level of cloud cover.

AWS provides two thumbnails for each scene, one quite small one that we used for our ‘recent images’ KML and one much larger. We have used the larger one even though it is too large to comfortably show at full resolution in Google Earth. To see the animation running at full size, click the link at the top right of the animation window.

Remember that Landsat imagery is very low resolution (about 30m per pixel) and these are just thumbnails, which are even lower resolution than that. So expect to only see very large scale changes. Look for changes in seasons, ice cover changes near the poles, lakes shrinking or growing, and even sand dunes moving.

A major problem is the large amount of cloud cover in the images. If you select only scenes with minimal cloud cover you end up with only a few images to work with. This highlights just how difficult it is for commercial providers to get good imagery.

One problem we had was that the images are not captured from exactly the same angle, so there was a significant amount of shaking in the animations. We have tried to fix this by reading the latitude and longitude metadata included with the scenes and moving the individual images appropriately. It is still not perfect as a browser cannot position an image at sub-pixel resolution.

Let us know in the comments if you find anything particularly interesting. Ideally tell us the path and row.

Here is an interesting tile in Chad that shows some fire scars.

The post Animating Landsat imagery in Google Earth appeared first on Google Earth Blog.

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What the…?

by StreetViewFun.com on Aug.23, 2016, under 3D Models, Argentina, Australia, Brazil, California, Denmark, England, Germany, Google Earth News, Google Earth Tips, Google Sky, Google maps, Hawaii, Indonesia, Ireland, Italy, Japan, Kenya, Mexico, Natural Landmarks, Netherlands, Sightseeing, Street Views, USA

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Street View car in the mirror

by Willi1 on Aug.22, 2016, under 3D Models, Argentina, Australia, Brazil, California, Denmark, England, Germany, Google Earth News, Google Earth Tips, Google Sky, Google maps, Hawaii, Indonesia, Ireland, Italy, Japan, Kenya, Mexico, Natural Landmarks, Netherlands, Sightseeing, Street Views, USA

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