"We can really fine-tune what we are seeing," she said.
The precision this technology offers is startling. To demonstrate, Silliman picked up a small plastic bag on his desk. Inside was a bullet that he recently recovered from a site at Tanyard Creek in Buckhead. Through global positioning he knew the exact location where the bullet was found. Examining its markings, he was able to tell it was a British-made bullet fired from model 1853 Enfield rifle. Because it was slightly marked, he could tell it had been rammed into a gun that had been fouled, probably from being shot a lot that day. Because the lead bullet didn't have any impact marks, he could tell it had not hit a target, but probably just traveled through the air, then dropped to the ground. Military records showed fighting at that location. Using mapping software showing modern Atlanta overlaid with Civil War fortifications, he traced back 1,100 to 1,300 yards the distance an Enfield-fired bullet would travel — to Rebel earthworks.
Silliman held up the little gray missile and declared confidently it was fired between 2 and 4 p.m. on July 20, 1864, by a retreating Confederate soldier. The Rebel missed whatever he was trying to hit.
A reporter asked Silliman if he was sure.
Silliman smiled slightly.
"Plus or minus 120 feet," he said.
Sitting in his small but ordered office in Smyrna, Silliman pulled up on his computer a topographic map of modern Atlanta. He then superimposed historical maps of Union and Confederate defenses, soldiers' camps and where battles took place. Red lines signified Confederate areas; blue showed Union areas. Purple showed areas that have been surveyed by archaeologists. Very little of metro Atlanta was purple.
Silliman, who with his lanky build and goatee could pass for a Union corporal, hopes to see that change with new technology.
He said for years traditional archaeology has focused on small sites that were inhabited for long periods, such as Native American villages. The Civil War, he said, requires a different approach especially in Georgia. Silliman, who was raised in New Hampshire but earned his graduate degree at Georgia State University, is the resident Civil War expert at Edwards-Pitman, a subcontractor that does environmental and historical assessments for companies and government agencies that are planning to develop land. Most of his work is in metro Atlanta for the Georgia Department of Transportation or agencies looking to see if any area has historical significance. Silliman insists that huge swaths of metro Atlanta do. The whole area for about a month in 1864 was one gigantic war zone.
"Essentially everything from here up to Chattanooga was battlefield," he said.
That includes the low hill near the Moreland exit, and hundreds of other places where the two armies fought around Atlanta. Under the earth, evidence of the fighting survives.
Douglas Scott, an archaeology professor in Nebraska nationally known as one of the pioneers in battlefield archaeology, said this technological transformation of archaeology "really has exploded, pun intended, in the last three or four years."
He said battlefield archaeologists in Europe, the eastern United States and the West have started using these tools, and now the South is embracing them. He said historical accounts, just like eyewitness testimony in a criminal case, couldn't always be trusted.
"There's a precision that goes with finding stuff on the ground," he said. "Think of historians as detectives; these tools help us find the forensic evidence."