How did the military survey Afghan's mineral deposits from airplanes?

June 13, 2010 8:55 PM

This recent MeFi post links to an intriguing article. In it is described a geological surveying technique. What fantastic technique is this? How does it work?

Armed with the old Russian charts, the United States Geological Survey began a series of aerial surveys of Afghanistan’s mineral resources in 2006, using advanced gravity and magnetic measuring equipment attached to an old Navy Orion P-3 aircraft that flew over about 70 percent of the country. The data from those flights was so promising that in 2007, the geologists returned for an even more sophisticated study, using an old British bomber equipped with instruments that offered a three-dimensional profile of mineral deposits below the earth’s surface. It was the most comprehensive geologic survey of Afghanistan ever conducted.

posted by cman to Technology (7 answers total)

I believe part of it might be Magnetic Anomoly Detection
posted by timsteil at 9:06 PM on June 13, 2010

Gravimetry is the general idea. The application is physical geodesy. The technology is a gravimeter.

For an example of the results, see this gravity anomaly grid for the coterminous US.
posted by jedicus at 9:07 PM on June 13, 2010 [1 favorite]

Gravimetry is used a lot, and it's not uncommon for them to serendipitously discover other things. An gravimetric scan of the Gulf of Mexico by an oil company found the remnants of the Chicxulub crater.
posted by Chocolate Pickle at 10:26 PM on June 13, 2010 [1 favorite]

The surveys were carried out by the USGS and the Afghan Geological Survey, not (directly) by the military, I think. The USGS Afghanistan website has a diagram -- look for the photo labeled "Geophysical Sensors" -- and a synopsis of the survey methods used. These pages deal with the 2006 surveys.

I've found nothing yet about the 2007 surveys that got the "3D" information. I suspect those may have used airborne electromagnetic soundings (EM; different from magnetic surveys in that they look at the response of rocks to artificial variations in both electrical and magnetic fields, not just to natural magnetic fields; a USGS examples is here). If I remember right, airborne EM has become a standard technique in minerals prospecting, at least for diamonds. I guess they could also have used magnetic gradiometry or vector magnetic surveys, too.
posted by paselkin at 12:22 AM on June 14, 2010 [4 favorites]

A few years ago when I still lived near a base with a lot of P-3s I got the impression that, in addition to their MAD gear, some of them might also be equipped with Ground-Penetrating Radar. Can anyone confirm?
posted by qbject at 7:53 AM on June 14, 2010

Potentially LIDAR? Ground pentrating Radar?

But, I always thought that one had to essentially drag a very heavy equipment package along the ground for LIDAR - doing it from the air may be possible, but I hope there was nobody underneath the screening zones...
posted by jkaczor at 8:24 AM on June 14, 2010 [1 favorite]

It looks like they used pretty common aerial magnetometer and gravity studies. Here is a link to USGS projects in Afghanistan.
posted by Big_B at 9:18 PM on June 14, 2010