THE ESTIMATION OF SOIL MOISTURE IN AGRICULTURAL FIELDS IN NAKHON RATCHASIMA PROVINCE, THAILAND USING RADARSAT-2 IMAGERIES

摘要

Due to the global warming in Thailand, characteristics of soil moisture have been very important for monitoring climate change and drought. In this respect, drought directly impacts on subsistence and usefulness of agricultural areas. However, due to the differences of topography and climate in various land uses, the volumes of soil moisture may be varying. Therefore, this research is proposed to generate maps of moisture levels by using C-band SAR and optical images at Nakhon Ratchasima province in northeastern part of Thailand. There are RADARSAT-2 images in standard mode (25m × 25m), dual polarization (HH and HV). The sigma nought/backscatter values are used to calculate statistical parameters of each pixel of the RADARSAT-2 image. This process uses mean, minimum, maximum and standard deviation of soil moisture in all coverage. To evaluate the accuracy of soil moisture estimated from RADARSAT-2 images, thirty positions in the study area were randomly selected and, at each sampled position, average soil moisture volume from ground measurement at 5 centimeter depth was then calculated which was used to compare with at estimated from RADARSAT-2 images. As a result, the soil moisture levels could be used to generate a trend of the soil moisture to use in a database for drought management.