Conducting out Topographical survey of Railway line section and yards as per requirement by aerial Survey using drone/ Unmanned Aerial System ( UAS ) and stereo photogrammetry technology and developing ESPs of existing/ proposed yards on same for various Construction projects of South Eastern Railway Construction Organization. Estimate Nos. 1792W/ 2019, 1695W/ 2016, 1924W/ 2022 & 1941W/ 2023.