2. Materials and Methods
2.1. Study Area
The study area for this research work was Wattana Nakhon District (102.4˚ E, 13.8˚ N), Sa Keao Province, of the Eastern Thailand (Figure 2.1). North part of the area is covered by a division of the Thaplan National Park. Paddy, cassava and permanent crops such as rubber and eucalyptus are cultivated in central and Southern parts of the district. Paddy agriculture area is a flat land which has an elevation varies between 10m to 100m. According to agricultural statistics in 2012/13 on this district as published by the District Agriculture Office, total agriculture land area is 445053 rai and the area cultivation of rice is 207338 rai?. Main rice cultivation season is the wet season rice cultivation, which starts from May to November by using rain-fed water. Dry season rice cultivation is less significant because of lack of water and optional crop cultivation like cassava and maze.
2.2.1. RS / GIS Data
MODIS gridded VI product with 250 m resolution (MXD13Q1) h27v07 tile was used as the main remote sensing data. The VI product from both Aqua and Terra Satellites) from 2013-05-01 to 2013-12-27 were utilized in this study (31 images from both platforms). ALOS Global Forest/Non Forest data set was used to identify the forest area in the study.
2.2.2. Field and Statistics Data
Filed visit and field data collection were done in selected paddy plots in Wattana Nakhon District throughout a one rice cycle, while satellite (images?) are being observed. The map of the field site location is shown in figure 2.2 and summary of the field sites are tabled in table 2.1. Plant height, water level in the field and canals and yield are collected in the field visit. Geo-tag photographs were taken in every visit to record and to see the change of paddy growth. Province- level agriculture statistics was obtained from Office of Agriculture Economics (OAE) and district- level agriculture statistics was taken from Wattana Nakhon District Agriculture Office.
Table 2.1 – Summary of the field data collection sites
Site No Location Village Cultivation Start Date Variety Cultivated
01 13.7397N, 102.346E M6, Ban Nongkum 10 July, 2013 Leuang Awn, Seed rate : 188 kg/ha
02 13.7559N, 102.347E M3, Ban Noongik 06 July, 2013 Khao Dawk Mali 105 , Seed rate : 188 kg/ha
03 13.7613N, 102.385E M14, Ban Wang Siaw 07 July, 2013 Khao Tah Haeng 17 , Seed rate : 188 kg/ha
04 13.7522N, 102.376E M9, Ban Tahg Luang 04 July, 2013 Khao Dawk Mali 105 , Seed rate : 188 kg/ha
2.3. Technology Method
The whole study can be divided in to four parts according to the achievements of the objectives. They are (1) Data pre-processing (2) Rice plant growth analyzing with VI, (3) Extracting rice acreage, Start of Season (SOS) mapping from VI Time Series and Accuracy assessment and (4) Rice yield analyzing with MODIS VI.
2.3.1. Data pre-processing
Vegetation index layers (NDVI and EVI), VI Quality...