# An IoT System and MODIS Images Enable Smart Environmental Management for Mekong Delta
## 3 Materials and Methods
### MODIS Data Products  
The Terra satellite, launched by NASA in December 1999 [22], is equipped with five instruments, including the Moderate Resolution Imaging Spectroradiometer (MODIS). The primary objective of the Terra mission is to observe various aspects of the Earth's atmosphere, ocean, land, snow and ice, and energy budget. Orbiting the Earth in a circular sun-synchronous polar orbit, the Terra satellite completes one orbit every 99 min and it crosses the Equator at 10:30 a.m. The MODIS sensor covers a range from visible, near-infrared, shortwave-infrared short-wavelengths to thermal infrared long-wavelengths, traveling from north to south on the daylight side of the planet. The MODIS sensor captures a wide range of wavelengths, from blue to thermal infrared, utilizing 36 bands. The spatial resolutions for bands 1-2, bands 3-7, and bands 8-36 are 250 m, 500 m, and 1000 m, respectively, as shown in Table 1[23].  
Figure 4: The deployment of a sensors station in the Mekong Delta area.  
Figure 3: The architecture of the sensors-based ground measurement station.  
In addition to the level-1 raw radiance data, the level-2 and level-3 MODIS data consist of various products related to the atmosphere, land, cryosphere, and ocean [24]. Since 2000, MODIS data products have been made available at different temporal resolutions, including daily, 8-day, 16-day, monthly, quarterly, and yearly. It is important to note that all MODIS data products are accessible free of charge.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Band** & **Bandwidth (nm)** & **Spectral Domain** & **Spatial Resolution (m)** & **Primary Use** \\ \hline
1 & 620–670 & Visible & 250 & Land/Cloud/Aerosol Boundaries \\ \hline
2 & 841–876 & Near Infrared & 250 & \\ \hline
3 & 459–479 & Visible & 500 & \\ \hline
4 & 545–565 & Visible & 500 & \\ \hline
5 & 1230–1250 & Shortwave Infrared & 500 & Land/Cloud/Aerosol Properties \\ \hline
6 & 1628–1652 & Shortwave Infrared & 500 & \\ \hline  
tmospheric Temperature \\ \hline
26 & 1360–1390 & Shortwave Infrared & 1000 & \\ \hline
27 & 6535–6895 & Thermal Infrared & 1000 & \\ \hline
28 & 7175–7475 & Thermal Infrared & 1000 & \\ \hline
29 & 8400–8700 & Thermal Infrared & 1000 & Cloud Properties \\ \hline
30 & 9580–9880 & Thermal Infrared & 1000 & Ozone \\ \hline
31 & 10,780–11,280 & Thermal Infrared & 1000 & Surface/Cloud Temperature \\ \hline
32 & 11,770–12,270 & Thermal Infrared & 1000 & \\ \hline
33 & 13,185–13,485 & Thermal Infrared & 1000 & \\ \hline
34 & 13,485–13,785 & Thermal Infrared & 1000 & \\ \hline
35 & 13,785–14,085 & Thermal Infrared & 1000 & Cloud Top Altitude \\ \hline
36 & 14,085–14,385 & Thermal Infrared & 1000 & \\ \hline \end{tabular}
\end{table}
Table 1: The MODIS sensor’s spectral bands and primary use [23].  
For this study, the primary data utilized are daytime Land Surface Temperature (LST) derived from the MOD09 GA and MOD11A1 land products, as well as PM mass concentration estimated from the MCD19A2 atmosphere product. These products can be obtained from the USGS Earth Data website [25] or retrieved through the use of Google Earth Engine [26]. To cover the whole Dong Thap Province, we need one scene at the horizontal-vertical location of 'h28-v08' on the global grid, and its acquisition time is at 10:30 a.m., correspondingly, as depicted in Figure 5. The images in the hierarchical data format (HDF) of earth observing systems are georeferenced to the sinusoidal datum. Subsequently, the image dataset is converted to the WGS84 geographic coordinate system from the Sinusoidal datum and saved in the Geo-tiff format. Finally, the images are clipped, ensuring they remain within the boundaries of Dong Thap Province.