In recent years, unmanned aerial vehicles (UAVs) have been actively applied in the agricultural sector. Several UAVs equipped with multispectral cameras have become available on the consumer market. Multispectral data are informative and practical for evaluating the greenness and growth status of vegetation as well as agricultural crops. The precise monitoring of rice paddy, especially in the Asian region, is crucial for optimizing profitability, sustainability, and protection of agro-ecological services. This paper reports and discusses our findings from experiments conducted to test four different commercially available multispectral cameras (Micesense RedEdge-M, Sentera Single NDVI, Mapir Survey3, and Bizworks Yubaflex), which can be mounted on a UAV in monitoring rice paddy. The survey has conducted in the typical paddy field area located in the alluvial plain in Tottori Prefecture, Japan. Six different vegetation indices (NDVI, BNDVI, GNDVI, VARI, NDRE and MCARI) captured by UAVs were also compared and evaluated monitoring contribution at three different rice cropping phases. The results showed that the spatial distribution of NDVI collected by each camera is almost similar in paddy fields, but the absolute values of NDVI differed significantly from each other. Among them, the Sentera camera showed the most reasonable NDVI values of each growing phase, indicating 0.49 in the early reproductive phase, 0.62 in the late reproductive stage, and 0.38 in the ripening phase. On the other hand, compared to the most commonly used NDVI, VARI which can be calculated from only visible RGB bands, can be used as an easy and effective index for rice paddy monitoring.
Karawang Regency, known as the National Rice Reserve, is experiencing drought on farmland. The Regional Disaster Management Agency (BPBD) of Karawang Regency noted that drought in 14 villages spread across three sub-districts in Karawang Regency has developed in 2019, such as Ciampel sub-district. Rice production decreased in 2015-2019 by 19 percent. The purpose of this study is to analyze the drought area of agricultural land using the Normalized Difference Drought Index (NDDI) and analyze the relationship between agricultural land drought and rainfall in Ciampel Sub-District, Karawang Regency in 2015 and 2019. The study used Landsat 8 OLI/TIRS in August-September 2015 and 2019. Agricultural land drought using the NDDI method is the ratio between the Normalized Difference Vegetation Index (NDVI) and the Normalized Difference Wetness Index (NDWI). The results showed a map of the distribution of agricultural land drought in Ciampel Sub-district, Karawang Regency during 2015 and 2019 with three classes of agricultural land drought (dry, rather dry, normal). The total area of agricultural drought in August 2015 was 11,166 hectares and as of September 2019 was 3,119 hectares. While as of September 2015, it was 3,086 hectares, and in 2019 was 3,158 hectares. The drought that hit Ciampel Sub-District in September 2019 hit almost all areas and dry areas in the middle eastern part of the Ciampel Sub-District. The drought, which is included in the classification of dry that hit irrigated rice field, was 20.19 %. Meanwhile, the rainfed rice field was 32.79%, and in dryland was 24.83%.
UAV-derived multispectral bathymetry is an alternative to creating a shallow water bathymetry map without a massive field survey. Multispectral UAV technology can be used for detailed scale identification scopes because it has better spatial resolution and relatively affordable cost. The UAV used in this study record the coastal area using four multispectral sensors, blue, green, red, and near-infrared bands. The UAV images are processed into point cloud information under the use of the Structure from Motion (SfM)based algorithm with a spatial resolution of 0.075 m. Then the point cloud information is used to predict the water depth using the random forest algorithm. This research was conducted at Pemuteran Beach, Bali, Indonesia. We compared the performance of only spectral, cloud point, and the combination of cloud point -spectral information to predict the water depth. As a result, the cloud point -spectral based shows significant accuracy improvement compared with the spectral only approach that reaches ~1.5, ~2.5 m, and ~0.3m for R 2 , RMSE, and MAPE, respectively. So, the use of the SfM UAV technique can improve the common spectral-based SDB method.
Sinkhole is a depression of the land surface, causing hazardous effects on the karst landscape. Land subsidence is a phenomenon of sinkhole formation due to karstification. Land subsidence associated with any of the existing evaporite-karst sinkholes Land subsidence is a gradual settling or sudden sinking of the Earth’s surface, which can be very dangerous as it relates to life on the surface and infrastructure planning. Ponjong and Semanu District, Gunungkidul Regency, are included in the Gunung Sewu Karst area, with landscapes highly influenced by the karstification process. Decision-makers need increasing attention to make assessments also mitigation on karst management. This study aims to determine the potential areas of land subsidence caused by natural factors in the karst landscape in the Ponjong and Semanu District, Gunungkidul Regency using integrated geospatial technology. For making some maps, we initially need a process from SRTM. Land Surface Temperature map, The Normalized Difference Vegetation Index (NDVI) map, slope map, and geological map are integrated into a GIS platform using the scoring and matrix then the overlay method. Descriptive spatial analysis of potential subsidence area is based on land surface temperature, vegetation factor, slope inclination, and geological formation related to altitude. The results show that approximately 80 percent of Ponjong and Semanu District places are high potential land subsidence areas. Policymakers can use this distribution of the potential regions of land subsidence as essential spatial planning in Gunungkidul Karst, especially in Ponjong and Semanu district.
Ci Manuk Flow Area is one of the river basins in Java Island. The Ci Manuk Delta changed from 1963 to 2002. Changes that occurred in the Ci Manuk delta were moved by extensive accretion. The reason for choosing Ci Manuk Delta is because the Ci Manuk flow has a high sedimentation rate compared to other flow areas, besides that, Sumedang Regency has built a dam to hold the sediment flow and repair floods. How this is done as a problem and research can be done to determine the delta-forming factors and changes in the delta region that occurred temporally from 2002 to 2018 after the dam was built. The method used in this research is spatial analysis and quantitative descriptive analysis. Spatial analysis is used to describe the spatial change in the temporary area and quantitative descriptive analysis is used to explain the results of the calculation of changes in delta area. The results of this study are the dynamics of delta changes that occur in the west are dominated by the addition of delta (accretion) with an area of 522.3 ha and undergo a change in shape from cuspate to birdfoot. The factors that support the addition of the area comes from internal factors, namely the high value of sediment and the low external factors originating from the marin.
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