"Today visitors to Gettysburg can climb to the cupola of the Lutheran seminary, where Lee stationed himself on July 2, the second day of fighting; or stand on Seminary Ridge, where the next day Lee watched from behind the Confederate lines as thousands of his men advanced across the open farmland to their deaths in the notorious Pickett’s Charge. But they won’t see what the general saw because the intervening years have altered the topography. Over the decades a quarry, a reservoir, different plants and trees have been added, and elevations have changed as a result of mechanical plowing and erosion. Geographic Information Systems, known as GIS, allowed Ms. Knowles and her colleagues to recreate a digital version of the original Gettysburg battlefield from historical maps, documented descriptions of troop positions and scenery, and renderings of historic roads, fences, buildings and vegetation." So very cool.