Journey through an ant colony. Courtesy of Texas A&M University.
Ground-penetrating radar has been used to nondestructively map an ant colony for the first time.
The results have been digitised and fed into an interactive visualisation system so that the colony can be explored virtually.
The system is inexpensive compared to earlier approaches and could be used in many fields.
Visitors at the SIGGRAPH conference in Los Angeles have been putting the system through its paces this week.
The colonies of leafcutting ants like the Atta texana are huge, spanning many metres underground.
"Leafcutting ant nests can hold a 3-storey house—the rural legend is that tractors can disappear into them," says Carol LaFayette, a fine artist by training who spearheaded the project.
Myrmecologists seeking to map out the colonies have resorted to painstaking methods such as scraping away soil layer by layer, or pouring a casting material into the colonies and then excavating the casts.
"My idea was to try to get an image of the ant colony that would leave the ants in place and also be able to be distributed," says Dr LaFayette.
The GPR data show the 3-D nest structure...
To do that, LaFayette contacted geoscientist colleagues at the university, who used ground-penetrating radar to map an Atta colony in rural Texas without displacing a single ant.
The radar returns a map of a vertical slice of earth, with the radar waves' arrival times dependent on the density within the slice. Tunnels show up as low density, the fungus on which the ants feed is higher, and the soil surrounding the tunnels higher again.
By shifting the GPR apparatus around inch by inch, an 8-by-8 metre region was investigated, resulting in 3-D map of the underground colony.
The team then fed the data into an "immersive visualisation" scheme. The GPR data are first spliced together and software then fills in the finer textural details.
The result is projected onto five screens arranged in a semicircle. Visitors then don stereo-vision glasses to give a true sense of space and use a handheld controller to navigate the virtual colony with an ant's-eye view.
...and software fills in the rest
Such immersive schemes have existed for years, but have been restricted to military and training applications, costing hundreds of thousands of dollars. The new visualisation system, developed by Texas professor Frederic Parke, uses off-the-shelf hardware and cost just $30,000 (Ł16,000).
"Bringing the cost down makes it more accessible to a wider range of disciplines and applications," Prof Parke said.
The group has been approached by archaeologists interested in visualising a Pueblo Indian site in Arizona as well as nautical archaeologists studying a Portuguese merchant ship that sunk in Lisbon harbour in the 17th century.
At SIGGRAPH, visitors expressing an interest have been as widely varied as palaeontologists, video game developers, and biologists. Prof Parke thinks the system could find wide application also in museums.
Plus, there's the aesthetic value of the approach. "When you're standing in front of the system and viewing these tunnel structures, it's quite colourful, quite beautiful," says Dr LaFayette. "From a distance it could look like abstract art, but it's also based in the science of this experimental way to view the nests."
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