August 11, 2008

Marble provides basic engine for free Google Earth replacement

Author: Bruce Byfield

The Free Software Foundation can cross off another item on its high priority list of applications that free software needs in order to compete. Version 0.6 of Marble, which ships with KDE 4.1, may not rival Google Earth just yet, but the underlying engine has the potential to do so in future versions. The main improvements needed to reach this stage are a lower level of detail and some additional views and integration into free online resources.

Marble is a new tool from KDE Education, the subproject already known for such educational tools as the annotated periodic table Kalzium and the astronomy program KStars. Like them, Marble is not just educational, but has all the makings of a handy reference utility as well.

Marble consists of a series of views of the world, ranging from a satellite view to a plain atlas view. Each of these views is available on a globe, a flat map, or a Mercator projection (a flat view that contains some distortions, such as an enlarged Greenland and diminished Australia, but which continues to enjoy popularity after 500 years). The first time you open a view, Marble takes 10 to 20 seconds to create it, but, after that, you can switch views within a few seconds.

You can further customize a view in Marble by switching to the Legends tab, where you can change what the map displays, choosing whether you want to view cities, or -- in the satellite or atlas views -- mountains, places of interest such as the poles and airports, and surface features such as ice caps and deserts, as well as map features ranging from a compass to lines of latitude and longitude. Although currently you can only turn off categories of features rather than choosing them individually, it is easy to imagine the Legend being extended to offer zoom views of features.

One or two of Marble's views, such as Earth at Night, are mostly eye-candy. Others, such as the precipitation and temperature views for December and July, are more immediately useful. It doesn't take much imagination to anticipate countless more views offering economic, geographical, and social information in the future.

Searching Marble

Whatever view you are in, you can search Marble in several ways. The first way is to drag with the mouse until you find the location you want. When you are viewing a globe, that can mean dragging the globe in any direction (which is why a compass is a standard part of the legend).

A more efficient way is to click on the Navigation tab. From this tab you can zoom in and out or re-center the view, as well as use a search field with automatic word completion to jump to a specific city. This feature is efficient, but currently incomplete, with minor cities not showing in a number of locations, apparently on an arbitrary basis, since one city of a certain size may be shown but another of the same size left off.

With the latest version of Marble, a third, more specific way to search has been added. When you are online, the OpenStreetMap view gives you a street-level map that you can save as a .JPG or .PNG graphic or print. However, like the city-level view, the street map view is currently incomplete, showing the main roads in some areas, but not many side streets. Presumably, though, this situation will eventually be improved, since you can select File -> Download New Data to update the available information.

Looking ahead

Marble is unlikely to rival Google Earth in certain areas. It is unlikely, for example, to offer continually updated satellite views or street images any time in the immediate future.

However, by the time Marble reaches its 1.0 release, there seems no reason why it could not equal Google's efforts on a more practical level. Some possibilities seem obvious. Links to Wikipedia could be easily implemented, and, the Marble project is already planning to link to Google's Panaramio. Similarly, once the OpenStreetMap data gains its missing detail, an address search function should provide the same functionality as Google Maps.

Marble is noticeably faster than Google Earth, and, like many of the applications written for KDE 4, benefits from the scalable vector graphics on the Plasma desktop. While the functionality is not yet what it could be, enough is in place to suggest that we now have a free license alternative to Google's network services. The question now is what we will choose to do with it.

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