In 1807, President Thomas Jefferson approved a survey of America's coastline to aid navigation. Nineteenth-century surveyors mapped the world through triangulation, beginning with one accurately measured distance, such as the 6.68-mile baseline on Edisto Island. Surveyors then selected a distant point and calculated the angle from each end of the baseline to that point, creating a huge triangle with one known side and two adjacent angles. Trigonometry then determined the lengths of the other two sides. By repeating this process and using old triangles as baselines for new ones, surveyors mapped large areas. Starting with a baseline on Edisto Island, triangulation was used to map South Carolina's shoreline, reducing shipwrecks and saving lives and money.