Estimation of Year of Construction of Bridges in Cambodia by Analyzing the Landsat Normalized Difference Water Index

Inspection data can be used to comprehend and plan effective maintenance of bridges. In particular, the year initial construction is one most important criteria for formulating plans, making budget allocations, estimating soundness. an survey bridges in Cambodia, it was concluded that only 54% 2439 surveyed known, with remaining 46% unknown. this research, Landsat satellite estimate these provides spatial spectral reflectance information covering more than 30 years, longer by visual judgement. However, limited image resolution means not possible shorter Instead, a method using Normalized Difference Water Index (NDWI) construction. Three pixels are selected from such way lies on current location bridge two other reference placed similar terrain at certain distance perpendicular axis. NDWI values plotted over time three difference value between pixel then compared. Before constructed, all should have values, but after target differ because surface different surrounding vegetation. By looking change, estimated. All Cambodian database classified into categories based length (which affects their visibility images) The results show estimated has same accuracy categories.