Latest satellite imagery brings continent into high-res focus
Posted August 14, 2009
Maps of Antarctica date back to when Roman geographer and astronomer Ptolemy envisioned a land in the southern hemisphere to counterbalance that in the north to satisfy an ancient sense of proportion. Terra Australis would remain terra incognita for more than 1,500 years, though that didn’t stop cartographers from drawing fanciful depictions of the southern continent, varying widely in size and location.
Today, the average person can zoom across Antarctica with Google Earth. It’s even possible to download high-definition images of ice and mountaintops thanks to an International Polar Year project that created a map mosaic of the continent from more than 1,000 satellite images — the Landsat Image Mosaic of Antarctica (LIMA) . [See previous story: Getting on the map.]
But Paul Morin knows those images and the maps created from them can get even better, practically proselytizing about a new promised land of high-resolution imagery in which one can literally count the boulders on the ground.
Morin, at the University of Minnesota , is the principal investigator for the Antarctic Geospatial Information Center (AGIC) , a National Science Foundation-funded project to archive and create just about anything to do with maps and imagery of Antarctica for science and logistics.
His team, which includes only one full-time person, has digitally archived, with assistance from the U.S. Geological Survey (USGS) Antarctic Resource Center and EROS Data Center , more than 330,000 aerial photographs of Antarctica at a resolution of 300 dots per inch (dpi). The USGS is continuing to rescan each image at a resolution of 25 microns (a quarter the width of a human hair) over the next 12 months.
“It’s Antarctica from 1947 to the year 2000, at anywhere from 20 centimeters to a two meter resolution per pixel. The entire collection fits on a single hard disk” Morin explained.
The historical aerial shots complement a rapidly growing, mind-boggling large reservoir of high-resolution imagery of Antarctica being taken almost daily now by a suite of commercial satellites, according to Morin. For instance, each individual pixel from a satellite called Worldview is about the size of a plastic grocery bag.
“We can actually see the tents in individual field camps,” Morin said. “Think of these satellites as on-demand air photography anywhere in Antarctica”
Much of AGIC’s efforts are currently concentrated on the McMurdo Dry Valleys, a 33,000-square-kilometer area partially devoid of ice. It is the site of a number of scientific studies sponsored by the NSF under the U.S. Antarctic Program (USAP) .
During the 2008-09 field season, Morin and members of his team spent about two weeks around an area called Bull Pass in the Dry Valleys collecting data to improve the accuracy of their maps. Using the satellite imagery, they identified individual boulders in the valleys prior to heading to Antarctica. Once in the field, they located the boulders in the pictures and used highly accurate GPS to plot the point, providing additional accuracy to the maps within two to four meters.
“So we now have absurdly accurate maps after two weeks of fieldwork in the central Dry Valleys,” he said, adding that his team is now working to complete a bound atlas of the region.
The group will return to Antarctica this upcoming season to geo-reference the southern end of the Dry Valleys, along with Ross Island, where the USAP’s McMurdo Station sits. That’s in addition to the 1.2 million square kilometers of imagery data that the team is still processing, representing nearly a tenth of the whole continent.
Scientists are already using the imagery and maps for ongoing projects, as well as to plan upcoming fieldwork. For example, Allan Ashworth , a paleontologist from North Dakota State University , and his colleagues are studying ancient glacial lake deposits in the Dry Valleys that contain evidence of a warmer, tundra environment that existed about 14 million years ago before the climate abruptly turned colder.
Ashworth said his team will use the data collected from its fieldwork with AGIC’s imagery to make detailed geologic maps.
“This is important for the representation of the data in publications we are working on, and, in turn, helps us with the interpretations of the landscape history of the Dry Valleys,” he explained. “For future projects, we will utilize the remote sensing capabilities of the images to help locate potential new study sites.”
Ashworth said that 14 to 20 million years ago, the tundra would have carpeted the valleys. But time has removed most of the deposits so that only a few patches remain.
“To locate deposits is like trying to find the proverbial needle in a haystack,” he said. “Before going into the field in [the] future, studies of the images will help us target certain areas for field studies — the images do not take away the need for field studies but will enable us to focus our field studies.
“What we have seen so far of the new commercial satellite imagery that is becoming available is fantastic,” he added. “Finally we have access to satellite images whose resolution is relevant to the landscape scales [where] we are working … The topographic and other data that can be derived from the images allows us with remote sensing and [mapping] software to model and view the landscape in ways previously not possible. In turn, this provokes questions that feed back into our research.”
Morin said AGIC is working with other science teams interested in surveying emperor penguin colonies or counting Weddell seals around the Ross Sea region. British Antarctic Survey (BAS) scientists using the LIMA imagery were able to identify the penguin colonies from the dark stains produced by the birds’ guano. AGIC’s imagery, with 900 times greater resolution, will allow the scientists to count the shadows of individual birds and estimate populations for large groups. [See previous story: The poop on penguins.]
Indeed, Morin said it is now possible to not only produce high-resolution maps of lakes and glaciers and penguin colonies, but scientists can tailor their requests in a variety of ways.
“Which direction do you want the lighting? What part of the season?” Morin said, throwing out examples. “Before it was, ‘Do you have a map of this?’ And now it’s, ‘Which map and what do you want to see?’”