This article appeared in today's issue of the Times of Israel, announcing NOVA's April 19 premier of "Holocaust Escape Tunnel" on all PBS stations in the United States.
Besides locating the Escape Tunnel from Pit 6 (where the "Burning Brigade" was confined, and what we call "Soviet Pit 1" (the first and largest of the extermination pits), we better pinpointed what we believe is the trench in the photograph. Alastair McClymont and Paul Bauman used electrical imaging to identify the fill material in the trench. We created a very high resolution digital elevation model (DEM) with contours of about 2 centimeters so as to see the subtle but distinct linear subsidence of the earth associated with the trench. And we used induced polarization to identify metal objects in the trench.
The victims were blindfolded, and marched through the trench into Soviet Pit 1. The archaeologists believed that as the victims heard gunshots from the Pit, and knew that they were being marched to their deaths, they would have emptied their pockets of their few remaining and most personal belongings, hoping that some day they would be found. As such, small metal objects identified in the geophysical surveys may provide more information about who these people were, and what was of greatest importance to them during their last few living moments.
Later, the Nazis and collaborating Lithuanians abandoned the use of the trench, and simply marched Jews directly into the pits, or up to the edge of the pits, and usually shot them in groups of tens.
Blogging by Paul Bauman