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Archive for July, 2007

Editing Google Earth

July 29th, 2007 No comments

London Eye - Blue ThamesIn the previous post I mentioned that my London Eye animation needed tweaking because of a colour change in Google Earth’s London aerial photos.  I’ve now fixed the file.

The issue occurred because the file masks GE’s imagery with a ‘photoshopped’ version of itself.  I did this to remove the aerial shot of the London Eye from the scene and clear the way for the animated shadow.

OK, so it’s probably not the most useful thing you can do in Google Earth  but here’s a quick overview of the method I used: 

  • In Google Earth (or Maps) save an image of the area you want to alter.  It makes things easier if the view is pointing directly downwards and due north. 
  • Edit this screenshot in photo/image editing software.   In this case  I just used GIMP‘s clone stamp tool,  and copied other bits of the imagery – mainly river – to cover those parts I wanted hiding.
  • Back in GE return to the place where you took the screen capture.
  • Add Image OverlayClick ‘add image overlay’ and open the edited photo.
  • By dragging the green boundary lines you can accurately stretch and shrink the overlay to the correct location. 
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Google Earth Imagery Updates

July 27th, 2007 1 comment

Yesterday Google provided another High resolution imagery and terrain update Google Earth.  Teasingly they haven’t provided a list of where the new data is, but given a series of cryptic clues instead.  The Digital Earth Blog has managed to piece many of these together if you want the answers.   (Edit 2007-08-01: Google have put full solutions here.)

One thing they have done, which I’ve sort of been expecting after they did the same for parts of Switzerland in an earlier update, is perked up the colours of some of some of the older data.  This includes the previously very brown London imagery now looking much fresher, with a blue river Thames and green vegetation.  The increased contrast provides a much more suitable backdrop for textured 3D models. 🙂 But it means I need to recreate the overlays for my London Eye animation… 

A Brighter London

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Full-Sky Temperature Maps in Google Earth

July 24th, 2007 1 comment

Microwave Sky in Google EarthMicrowave Sky in Google Earth

Five more Universe temperature maps from NASA’a  Wilkinson Microwave Anisotropy Probe (WMAP), covering different frequency bands.

These were used by the WMAP team to subtract the galactic signal and produce the Cosmic Microwave Background map.  The wide red band across the centre of each is the microwave emission from our galaxy.

Created using the same technique as the CMBR file these are viewable in Google Earth from the outside and inside.  Jpeg compressing these maps is next to impossible without introducing a bundle of artifacts, so the file is kind of on the large side.

Full-Sky Temperature Maps(7.2MB)

Credit: NASA/WMAP Science Team.

On a related note:  Google launched their NASA collaboration last week with some new default layers Google Earth –  under ‘Featured Content’. If you haven’t checked it out already, do so. 🙂 The ‘Earth City Lights’ views are impressive – very cool how it’s possible to make out features like coastlines, river, roads and even the Trans-Siberian railway. But don’t miss the amazing overlays in the Satellite Imagery section – you need to click on the links in the description text of the blue placemarks to get these to appear.

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Cosmic Microwave Background Radiation in Google Earth

July 21st, 2007 2 comments

Cosmic Microwave Background Radiation Map, wrapped around Google EarhMicrowave Sky. Google Earth Backdrop

Moving up in scale from my Google Earth Solar System model, this file displays the all-sky microwave background map of the universe produced by NASA’s Wilkinson Microwave Anisotropy Probe (WMAP).

The Microwave Sky (700kB)

From the WMAP website:

The detailed, all-sky picture of the infant universe from three years of WMAP data. The image reveals 13.7 billion year old temperature fluctuations (shown as color differences) that correspond to the seeds that grew to become the galaxies… This image shows a temperature range of ± 200 microKelvin.

The file provides options to view the map from the outside looking in, and also from the inside looking out. To enable this I simply placed the same image overlay 2 different altitudes in GE – ground level and 80000000m (effectively infinity). With the second option you’ll notice some slight image break-up when looking towards the poles. Nevertheless it gives an interesting inside view.

The major hurdle I had to overcome in getting this into Google Earth is that the published WMAP image uses a different map projection, Mollweide, from the Equidistant Cylindrical required for the free Google Earth.  I converted between the two formats using the powerful, but not very well documented GDAL command line utilities – part of  the open source GIS kit FWTools.  I’ll go into more detail on the method in a future post.

Credit: NASA/WMAP Science Team

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Solar System in Google Earth

July 18th, 2007 16 comments

Solar System in Google EarthFollowing on from my Google Earth vs moons add-on,  here’s another size comparison which includes all the planets too.

I’ve used an image overlay to ‘convert’ Google Earth into the Sun, and arranged 45, scale, 3D models of Solar System bodies next to it. The file can be downloaded here:

Solar System in Google Earth (7MB)

Visually, it works better if Google Earth’s atmosphere is switched off (View -> Atmosphere).

The large differences in size make this much harder to navigate than the moons file, but you can fly straight to a particular body by clicking on the appropriate model name or placemark under Places.  Also, the glare(!) from the sun overlay can be annoying at times,  but this can be toggled off.  

As with the moon models the planet textures are based on real imagery,  and come from the public domain sources listed below.

Credits

  • Venus, Jupiter, Saturn – Björn Jónsson 
  • Neptune, Uranus – NASA/JPL/Hastings-Trew/Thomas
  • Mercury, Pluto – NASA/JPL/Seal/Rawlings
  • Mars, Earth – USGS

Related Posts:
The many moons of Google Earth
How to create textured globe 3d models

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