National Geographic : 1956 Mar
336 Shivering Surveyor in the High Andes... Mapping the still largely uncharted con tinent of South America, U. S. and Latin American engineers and soldiers are swarming up 18,000-foot peaks, camping in jungles, and exploring the Amazon's headwaters. Eighteen countries, including the United States, are working on the program, which is coordinated by the Inter-American Geodetic Survey (or IAGS), a mapping agency of the U. S. Army. Before maps can be made, geodetic sur veyors must crisscross each country, put ting in basic controls identified by bronze disks painstakingly established as to lati tude, longitude, and elevation, and firmly fixed in concrete or stone. All parts of + Colored Lights Guide Engineers When a survey leads through a city, engineers set up their instruments on the highest building available. To distinguish their station lights from street lamps and neon signs, they may use prearranged groupings of colors. Red, white, and blue signals flash at sunset on this clock tower in Diriamba, Nicaragua.