Tahun 2012, Dua paper Dr. I Wayan Nuarsa diterbitkan di Jurnal Internasional, Inggris dan Kanada
Using variance analysis of multitemporal MODIS images for rice field mapping in Bali Province, Indonesia
I Wayan Nuarsa, Fumihiko Nishio, Chiharu Hongo, and I Gede Mahardika. International Journal of Remote Sensing, UK. Volume 33, Issue 17, 2012.
Existing methods for rice field classification have some limitations due to the large variety of land covers attributed to rice fields. This study used temporal variance analysis of daily Moderate Resolution Imaging Spectroradiometer (MODIS) satellite images to discriminate rice fields from other land uses. The classification result was then compared with the reference data. Regression analysis showed that regency and district comparisons produced coefficients of determination (R 2) of 0.97490 and 0.92298, whereas the root mean square errors (RMSEs) were 1570.70 and 551.36 ha, respectively. The overall accuracy of the method in this study was 87.91%, with commission and omission errors of 35.45% and 17.68%, respectively. Kappa analysis showed strong agreement between the results of the analysis of the MODIS data using the method developed in this study and the reference data, with a kappa coefficient value of 0.8371. The results of this study indicated that the algorithm for variance analysis of multitemporal MODIS images could potentially be applied for rice field mapping. Online Access.
I Wayan Nuarsa, Fumihiko Nishio, and Chiharu Hongo. Journal of Agricultural Science, Canada. Volume 4, No 3, 2012.
Forecasting rice yield before harvest time is important to supporting planners and decision makers to predict the amount of rice that should be imported or exported and to enable governments to put in place strategic contingency plans for the redistribution of food during times of famine. This study used the Normalized Difference Vegetation Index (NDVI) of Landsat Enhanced Thematic Mapper plus (ETM+) images of rice plants to estimate rice yield based on field observation. The result showed that the rice yield could be estimated using the exponential equation of y = 0.3419e4.1587x, where y and x are rice yield and NDVI, respectively. The R2 and SE of the estimation were 0.852 and 0.077 ton/ha, respectively. An accuracy assessment of rice yield estimation using Landsat images was performed by comparing the rice yields from the estimation result and the reference data. The results show that the linear relationship with the R2 and SE of the estimation were 0.9262 and 0.21 ton/ha, respectively. The R2 is greater than or equal to 0.8, which demonstrates a strong agreement between the remotely sensed estimation and the reference data. Thus, the Landsat ETM+ has good potential for application to rice yield estimation. Online Access.