Estimating Rainfed Rice Yield of Thailand in 2003 Using RADARSAT Data

摘要

Radar satellite data has a great potential in various applications. To take advantage of thernradar data, multi-temporal RADARSAT C-HH imagery were applied to extract information onrnrainfed rice area. Rainfed rice area mapping normally has limitation in terms of imageryrnreceiving time especially during raining season. Radar imagery are effective because radarrnwavelengths can penetrate through cloud, haze, and rain. The purpose of this study is to applyrnRADARSAT imagery and geoinformatic data to monitor rainfed rice area, and to estimate ricernyield by GIS modelling. Field surveying on four test sites was performed to verify the results ofrnthe model. The four test sites were Chiang Rai, Surin, Nakhon Si Thamarat, and Nakhon Nayok;rnthey were chosen because they represented different rice management practices in the fourrnregions of Thailand. Supporting data, which are climate, geomorphology, soil, and socio-economic,rnwere collected and included in the model. The procedure of RADARSAT imageryrnpreprocessing include data input, image enhancement, image geometric correction, specklernnoise filtering and image mosaic. The rainfed rice areas were derived from multi-temporal datarnusing visual interpretation. For this analysis, optimal time for data acquisition during rainfed ricernarea period needed to be identified. Ground truth data were collected simultaneously with thernRADARSAT observations. Then, rice production simulation model was employed to estimaternrice yield in each site.rnThis paper deals with the results obtained from this research, we found that the total rainfedrnrice area of Chiang Rai using imagery acquired on 14, 21 September 2003, 4, 21 August 2003,rnand 4, 11 July 2003 was 304,393 hectares; Surin using imagery acquired on 8, 15 July 2003, 1, 8rnAugust 2003, and 6, 23 December 2003 was 302,968 hectares; Nakhon Si Thamarat usingrnimagery acquired on 4, 11 September 2003, 15, 22 November 2003, and 9, 26 January 2003 wasrn60,703 hectares; Nakhon Nayok using imagery acquired on 28 September 2003, 29 Octoberrn2003, and 16 December 2003 was 100,688 hectares. Then, the accuracy of image interpretationrnwas verified using a Simple Random Sampling. It was revealed that the accuracy of rice arearnestimation in Chiangrai, Surin, Nakhon Si thamarat and Nakhon Nayok province werernrespectively 84, 84, 83, 82 percent accurate. The results of rice yield estimation on each siternshowed that Chiangrai has rice yield of 467.45 yield/rai, Surin 343.8, Nakhon Si Thamaratrn326.46, Nakhon Nayok 354.91 yield/rai.