What’s new in Earth 3D
What is the hardware configuration required to install this software?
The program also uses QT and OpenGL to view planet Earth. It downloads the height field and texture data on request over the internet. You require at least DSL speed to use it.
Where does the height field and texture data come from?
The data is transparently downloaded from a web server that contains around 1.5 GB of data. This data belongs to USGS, NASA and city of Osnabruck.
Can the full dataset be downloaded?
The full dataset is available currently from a link. The file is 1.1 GB ZIP file. The file can be downloaded and used for running the program on machines that don't have the required bandwidth to load the data over the internet. For using it, you should extract it somewhere. Start earth3D and then click on magnifying glass icon in the left corner of window. Select “URL” and then click on “Browse files”. Select the file service/earth.sxml from extracted files and then click OK. The 5 earth maps will appear on the left in tree view.
Sometimes a message “/usr/lib/libGL.so.1: version information is not available” is displayed. What could be the problem?
When you encounter such message, the first thing that you should do is check your OpenGL driver and graphics card driver. Frequently people use ATI graphics card driver but do not use drivers from ati.com. Therefore, if you have a ATI graphics card on your computer then you should try and install the ATI's graphics card driver.
How is server data organized in earth 3D?
Firstly, there is service.sxml file which describes the maps that are available. The file provides information about icons of each map. It also contains information about the exact location of geometry.mxml file. This geometry.mxml file has links that allow us to access the root node of texture and heightfield tree. Each node in these trees has some data about itself and links to 4 subtitles. The trees describe a quad tree. This means the tree begins with a map that has a size of 256x256 pixels. The map contains the whole Earth. The map is partitioned into 4 quarters and each quarter is saved again with size of 256x256 pixels under parent node. Therefore, with each layer of the tree, resolution of map doubles.
Every map in the tree has a small map that has a size of 256x256 pixels. Every node also has 4 links to other nodes. Links normally are URLs that are either absolute or relative. Thus, you can save parts of every map on another server (e.g. a single continent or country).
You can save height field map tiles in PNG format while texture map files can be saved in JPG format. To save binary data and XML data in these files (geometry.mxml, service.sxml and in tree nodes) a very simple file format is invented. The size and number field in this file format are very simple ASCII-Numbers that are followed by linefeed character.
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