USGS Air Photography

 

 

AGIC now maintains all trimetrogon aerial (TMA) photography and flight indices of photos taken in the Antarctic from 1946-present.  The collection is comprised of >330,000 air photos, which were collected and scanned by the USGS EROS Data Center.  Photos currently available have been scanned at medium resolution (400 dpi);  high resolution air photos will be available by June 2010.

 

 

 

 

Trimetrogon photography is a system of aerial cameras where one vertical and two oblique pictures are taken simultaneously for topographic mapping purposes.  Thus, images in this collection are either the vertical photograph (taken on nadir; designated by a "V" in the file name) or left or right obliques (at a 45° angle off-nadir; designated by either L or R) taken along a single TMA flight line.  Not all flights were equipped with oblique cameras, and camera malfunctions sometimes limited the availability of a complete set of photos.

 

 

 

To successfully navigate AGIC's collection of Antarctic TMA air photos, you will need a few pieces of information.  The naming convention explained here was designed by the USGS in this way:

 

1). TMA flight line number is identified by the first 4 numbers in the file/folder name, regardless of the letters that precede them (ABCA, ABC, or CA).

 

2). V, R, and L in a file/folder name designate the orientation of the camera used to take the picture: vertical, right, or left.

 

3). The last 4 numbers in the file name of a photo designates the frame number along the flight line.

 

4). The higher-numbered flight lines are typically the most recent.

 

As an example, if you are looking for TMA flight line 3112, you would begin your search by clicking the folder below labeled "ABCA31".  Clicking ABCA31 will then bring you to a set of folders designating all flight lines that begin with "31".  The first 4 digits in the name of the folder (e.g., ABCA3112) designates the TMA flight line number.  The letter at the end of the folder name will designate vertical (V), right (R) or left (L) photos.  The photos themselves are contained within each flight line folder.  The 4-digit photo number is appended to the end of the file name (e.g., vertical (V) photo number 0063, [photo number 63] along TMA flight line 3112, has this file name: CA311200V0063).

 

Thus, if you are looking for vertical photo number 63 along TMA flight line 3112, you would click on ABCA31 below, navigate to the folder titled, "ABCA3112000000V", then navigate to the photo titled, "CA311200V0063.tif".