地理信息学与地统计学：概述

The Role of Surveying and Mapping in Setting Out of Itu Irrigation and Flood Control

Ugwuoti AI and Nwosu KI

Geomatics Science (Surveying and mapping) is the science and art of determining the precise positions of points and dimensions of features above, on and beneath the earth’s surface. It is indispensable in all meaningful environmental development. This is buttressed in the case of Itu irrigation and flood control project in Akwa-Ibom State, Nigeria which was designed to facilitate all year round farming on a farm land beside Itu river. The project was achieved by the application of series of Surveying and mapping processes ranging from Control extension, setting out of setback lines, Traversing, Area Computation, Setting out of Dyke alignment and farm roads, Grid Data processing, Plan Presentation to report writing. The instruments employed were Trimble TSC2 Differential Global Positioning System and its Accessories, Wild T2 theodolite and accessories, and a Standardized 100 m Steel Tape. The project seats on a 32.805 hectares of land. The grid and spot heights were at 50 m intervals along the distributor drains. From the spot heights, the highest reduced level within the farm was 5.437 m and the lowest reduced level was 2.760 m. The linear accuracy of the work was equal to 1/43,000 and the elevation differences were 2.677 m. The following plans were produced: Boundary plan, Spot height plan, Contour Plan on a Two Dimensional view standard Channel irrigation structure depicting the Setback from river bank, dyke alignment, farm roads, distributor and collector drains.