 Initially appointed a brevet second lieutenant in the 5th U.S. Infantry , within a few weeks Raynolds was transferred to the U.S. Army Corps of Topographical Engineers . The Topographical Engineers performed surveys and developed maps for army use until their merger with the Corps of Engineers in 1863 . Raynolds 's first assignments from 1843 to 1844 were as an assistant topographical engineer involved in improving navigation on the Ohio River and surveying the northeastern boundary of the U.S. between 1844 and 1847 . 
