Archeologists Drew Wise, left, and Michael Seibert use shovels to clean a trench dug in the Vicksburg National Cemetery Tuesday. A team of archeologists used ground-penetrating radar in January after an unmarked burial site was found while a new burial spot was being prepared. Archeologist Jessica McNeil said the team is now doing ground truthing, a technique to confirm the radar data, during which soil discolorations are studied to confirm burials. The digs are 6 inches to 8 inches deep, so they won’t disturb the graves. The national cemetery, on the western boundary of the Vicksburg National Military Park, is one of the largest Civil War burial sites in the United States. It was established by Congress in 1866 and contains 17,000 Union Civil War dead, including 13,000 unknown.