Mangrove ecosystems are one of the blue carbon parameters with large carbon storage capabilities. The carbon sequestration is crucial in addressing the greenhouse effect that causes the rise of carbon emissions in the atmosphere. One of the measurements that can be made is the estimation of mangrove above-ground biomass (AGB). This is due to the binding of carbon stored in the form of mangrove biomass. The aim of this research is to estimate and map the spatial distribution of mangrove above-ground biomass (AGB) is conducted using WorldView-3 (WV-3) image, a high spatial resolution remote sensing data. We used Normalized Difference Vegetation Index (NDVI) and Soil Adjusted Vegetation Index (SAVI) to estimate mangrove above-ground biomass (AGB). Field data obtained from measuring mangrove tree diameter at breast height (DBH) which is then calculated using the allometric equation. We conducted regression analysis between field data and vegetation indices (NDVI and SAVI) to determine the most accurate vegetation index for estimating mangrove above-ground biomass values varied across the mangrove forest. This results of this research shows that the NDVI vegetation index provided higher accuracy for mangrove AGB estimation than SAVI index with R2 of 0,603 and resulting the AGB value between 750 to 1.300 kg/m2.
Active system remote sensing technology is increasingly developing in extracting information on the biophysical aspects of mangrove vegetation, such as mapping the percentage of canopy cover. Mapping the percentage of mangrove canopy cover is essential to maintain the stability of coastal ecosystems. This study uses airborne LiDAR data based on the First Return Cover Index (FRCI) to map and analyze the variation and spatial distribution of the canopy cover percentage in the Ratai Bay mangrove forest, Pesawaran, Lampung, Indonesia. This study aims to (1) Analyze the variation and spatial distribution of the percentage of FRCI-based mangrove canopy cover using LiDAR data and (2) Calculate the accuracy level of the mapping results. FRCI is a LiDAR point cloud data rasterization algorithm that calculates pixel value information from canopy cover recorded by airborne LiDAR. The canopy cover value at each pixel and the regression function obtained from field measurements were integrated to build a model to obtain a map of the percentage of mangrove canopy cover. The resulting map identifies that the Ratai Bay mangrove forest is dominated by the dense and evenly distributed canopy cover class with a mean cover value of 89.78%, generally found in almost all study areas. This FRCI-based mangrove canopy cover percentage mapping has high mapping accuracy with minimum and maximum accuracy values of 92.31% and 93.09%, respectively. The results of this study indicate that the biophysical aspects of mangrove vegetation, especially canopy cover, can be mapped using LiDAR data with the FRCI algorithm.
Updating information on rice fields is very important to pay attention to environmental quality and food security. This is related to Indonesia's commitment to achieving Sustainable Development Goal number two in terms of agricultural data collection and analysis. Remote sensing can be used as an alternative method for identifying and mapping land cover, for instance paddy fields. Land cover in paddy fields varies greatly according to paddy growth phase, wherein these growth phase can be shown by different spectral reflectance values in remote sensing imagery. Mapping of paddy fields based on their spectral reflectance began to be widely carried out in Indonesia. Therefore, the aims of this study were to determine the spectral reflectance pattern of temporal paddy growth phase then form a map of the paddy fields based on those spectral libraries. This study used Spectral Angle Mapper (SAM) method to identify paddy fields on Landsat-8 OLI determined from spectral reflectance pattern of paddy-growth phase in some areas of Subang and Indramayu Regency in one growing season. The results succeeded in classifying paddy fields and non-paddy fields area. Classified paddy fields consisted of several land covers comprising the bare-land, inundation-land, vegetative, generative, and ripening. The accuracy test showed an overall accuracy of 70.07%. Misclassification in this study occurred due to the existence of thin cloud cover, besides there was a misclassification between built-up area and the bare land.
The emergence of remote sensing images with high spatial resolution has increased the advancement of image-based information extraction methods. One of the rapidly developing approaches for mapping and analyzing high spatial resolution images is the object-based approach, also known as geographic object-based image analysis (GEOBIA). This development makes it possible to quickly and accurately distinguish between vegetated and non-vegetated objects in vegetation study. This study aims to (1) create a ruleset to discriminate vegetated and non-vegetated objects from a high spatial resolution image, (2) apply the GEOBIA approach to map vegetated and non-vegetated objects, and (3) calculate the accuracy of the mapping results. The GEOBIA approach was applied to a WorldView-2 image (2 m pixel size and eight multispectral bands) of the Clungup Mangrove Conservation area, Malang, East Java, Indonesia. We assessed the ability of all of the WorldView-2 image bands for discriminating the targeted objects. The segmentation process in GEOBIA used a multi-resolution segmentation algorithm using the normalized difference vegetation index (NDVI), and the image classification used a rule-based classification technique. The green, red, and near-infrared bands can effectively distinguish the targeted objects based on the developed ruleset. The classification result shows that the vegetated and non-vegetated classes fall within their corresponding objects on the image. We implemented an area-based accuracy assessment that assesses both positional and thematic accuracy of the mapping result, based on the visual interpretation of the pansharpened WV-2 image (0.5 m pixel size) as a reference for the accuracy assessment. This process results in a 74,06% accuracy, meaning that the combination of GEOBIA and WorldView-2 image produces high accuracy of vegetated and non-vegetated objects map.
Mangrove ecosystems have a significant role in absorbing carbon emissions in the atmosphere used as photosynthetic materials. Absorbed carbon emission is stored in the form of biomass in vegetation, of which 47% of the biomass is aboveground carbon stock (AGC). Monitoring the AGC needs to be carried out efficiently, consistently, and sustainably to increase efforts to prevent global warming, and remote sensing imagery has the potentials to address this issue. This study aims to (1) explore the relationship between the selected vegetation indices derived from the WorldView-2 image and the corresponding AGC measurement in the field and (2) estimate and map the spatial distribution of AGC of mangroves. This research was conducted in a mangrove forest in Clungup Mangrove Conservation area, East Java Province, Indonesia. We applied allometric equations to determine the value of vegetation biomass in the study area based on the tree diameter at breast height (DBH), which will then be converted into carbon stock value. For AGC estimation and mapping purposes, we used Normalized Difference Vegetation Index (NDVI), Simple Ratio (SR), Rededge Simple Ratio (SRre), and Combined Mangrove Recognition Index (CMRI). We used correlation and regression analysis to evaluate the statistical relationship between these vegetation indices and field AGC data. Our findings suggested that the SR has the highest accuracy in modeling AGC with an R2 value of 0.124. Thus, it results in a range of AGC from 0.127 tons/pixel to 0.414 tons/pixel in the study site.
Spectral reflectance of objects provides key recognition of objects from remote sensing data. Each surface objects have their own specific spectral reflectance pattern that acts as a spectral fingerprint for object discrimination. This study aims to evaluate the effectiveness of radiometric correction applied to WorldView-2 image by comparing the image correction result with field spectrometer measurement. Some objects were chosen as the basis for observing object spectral reflectance, namely grass, non-mangrove vegetation, mangrove vegetation, soil, and asphalt. The WorldView-2 image was radiometrically and spectrally corrected up to at-surface reflectance level using provided procedures. For reference, the spectral reflectance of selected objects were collected in the field using a JAZ EL-350 field spectrometer (340-1028 nm). In order to perform a direct comparison and evaluation, the results of object spectral reflectance of field spectrometer were resampled based on the center wavelength of WorldView-2 image bands (i.e. from thousand to eight bands). This study found that the spectral reflectance patterns of all targeted objects were similar. However, the most accurate spectral reflectance of WorldView-2 image object was asphalt. Asphalt has high colour homogeneity and relatively stable in a long period of time. This study shows that the standard image radiometric and spectral correction approach is effective to represent the spectral reflectance of objects on Earth surface.
Providing accurate and up-to-date agricultural vegetation maps is a very important task for agricultural land evaluation and monitoring. These maps allow various kinds of spatial analyses could be conducted to optimally manage and utilize of land resources. One of the newly developed approaches in information extraction from remote sensing data is objectbased approach or widely known as Geographic Object-Based Image Analysis (GEOBIA). This study aims to utilize GEOBIA and a pan-sharpened WorldView-2 image (0.5 m pixel size) to identify and map agricultural vegetation types in part of Dieng Plateau, Central Java, Indonesia. A multiresolution segmentation algorithm was used to partition the image into vegetation object candidates based on some segmentation criteria. The accuracy of segments created were evaluated by visually comparing the segmentation result with the objects border on the image and field visit. A hierarchical conceptual model was created to systematically classify targeted agricultural vegetation objects, and the relevant interpretation keys for each object were identified. For the classification process we implemented a rule-based classification based on segment’s values, shape, homogeneity, texture, compactness, asymmetry, roundness, elliptic fit, number of pixel and border length. The result showed that the combination of GEOBIA and WorldView-2 were able to discriminate and map the types of agricultural vegetation into cabbage, carica, carrot, chili, potato, potato with soil solarization, and tamarillo with a reasonably high accuracy.
Geographic Object-Based Image Analysis (GEOBIA) is an emerging approach in remote sensing image analysis and classification which relies on segments or objects created by a group of pixels on the image. GEOBIA has been utilized for many remote sensing applications with various degree of success. However, from the literature, its application for landform analysis and classification is still rare. This study aims to test GEOBIA interpretation capabilities to identify landform in part of Opak Watershed (Central Java, Indonesia) using Landsat 8 OLI and DEMNAS imagery (30 and 8- meters pixel size, respectively) and evaluate the result. Both image data were fused to create an image with high spectral and spatial resolution and contains elevation data, as an input for the segmentation process. GEOBIA interpretation process was performed gradually; first, initial Multiresolution Segmentation Algorithm was conducted to identify the variation of slope found in the study site. Then, the slope segments/objects were used to identify landform using Ruleset-Based Classification considering the image object information including object values, pattern, shape, and other parameters. The accuracy of the result was evaluated based on the percentage accuracy of the landform classification. From this study, we found that fusion-image and GEOBIA are capable of distinguishing landform elements very well with the percentage of overall accuracy is 88%. This result shows that GEOBIA has potential in identifying and classifying landform objects.
Land Surface Temperature (LST) is an important indicator of environment changes, especially related drought monitoring. It is necessary to accurately detect drought events using advanced technology proved information regarding the drought areas. Remote sensing images have proven to be efficient in detecting drought events. MODIS Terra and Landsat 7 ETM+ (Enhanced Thematic Mapper Plus) and Landsat 8 OLI/TIRS (The Operational Land Imager and the Thermal Infrared Scanner) represent remote imaging images with different spatial resolutions that enable us proved drought information. However, proper methods are needed to optimize these images for monitoring drought events. The purpose of this study is to find out the ability of multi-scale images proved information about drought monitoring using LST methods. The method used in LST is Temperature Condition Index (TCI), Crop Water Stress Index (CWSI), and Principal Component Analysis (PCA). All three equations are selected because they represent a modification of the method for LST input. The results suggest that the three equations used in multi-level imagery have a critical alignment of information regarding drought. The results show that drought pattern identified by MODIS Terra image was similar to the one detected by Landsat ETM+ and OLI/TIRS images. However, we found a temperature difference in dry season (especially in October) between Landsat ETM+ and OLI/TIRS. The degree of LST estimation accuracy between MODIS Terra and Landsat (ETM+ and OLI/TIRS) is indicated by the average difference between the results of those images, which was 1 degree Celsius (1°C). The use of these three equations for drought monitoring with multi-level imagery suggests that there is a positive relationship. This relationship manifests the same pattern, shape, and association that are produced, thus using a common equation for drought monitoring is more focused.
Image segmentation is the most important stage on Geographic Object Based Image Analysis (GEOBIA). The result of segmentation affects the final accuracy of classification. One of the applications of image segmentation operations is to delineate vegetation objects. Further analysis of vegetation could be used for inventory of natural resources, agricultural, land cover, land use, etc. However, applying image segmentation for separating vegetation types is challenging due to their irregular shapes and various patterns and colors. This study aims to determine the optimum parameters of image segmentation for delineating vegetation types using a pan-sharpened WorldView-2 image (0.5 m pixel size) which was acquired on August 2018. Combinations of scale parameter and composition of homogeneity criterion (shape and compactness) were systematically simulated to obtain the best segmentation parameters. The result of segmentation was assessed quantitatively based on visually interpreted image map as a reference. This study found that application of shape and compactness simultaneously for vegetation extraction would produce rough segmentation result. The optimum parameters for segmenting vegetation types using WorldView-2 were using scale parameter of 5, shape of 0 and compactness of 0.5.
Coral reef live percent cover (LPC) mapping has always been a challenging application for remote-sensing. The adoption of machine-learning algorithm in remote-sensing has opened-up the possibility of mapping coral reef at higher accuracy. This paper presents the application of machine-learning regression in the empirical modeling of coral reef LPC mapping. Stepwise regression, Support Vector Machine (SVM) regression, and Random Forest (RF) regression were used model the percentage of live coral cover in optically shallow water of Parang Island, Central Java, Indonesia using field photo-transect data to train the PlanetScope image. PlanetScope multispectral bands were transformed into water column corrected bands, Principle Component bands, and Cooccurrence texture analysis bands to be used as predictors in the regression process. The results indicate that the accuracy of machine learning algorithm to map coral reef LPC is relatively low due to the radiometric quality issue in the PlanetScope image (RMSE = 15.43%). We could not yet fairly justify the performance of machine learning algorithm until we applied the algorithms in other images.
Mangrove species inventory and mapping is very important as an effort to preserve the ecosystem and biodiversity of mangrove forests. One way of efficient mangrove species inventory and mapping is to use remote sensing imagery, especially through the analysis of its spectral reflectance pattern. This study aims to map the fourteen mangrove species on Karimunjawa Island, Central Java, Indonesia by: (1) measuring the mangrove species spectral reflectance pattern in the field, (2) characteristic analysis of the mangrove species reflectance pattern, and (3) mapping the dominant mangrove species distribution. The spectral reflectance measurement of mangrove species objects in the field was done by using JAZ EL-350 VIS-NIR (ranges from 300 to 1100 nm). The JAZ field spectrometer was pointed at a distance of 2 cm from the target objects with 10 reading repetitions for each species. Field measurements results were then taken to the laboratory for analysis of spectral reflectance and absorbance patterns, which served as key object recognition in this study. To combine the field and image spectral reflectance patterns, the field reflectance patterns were resampled to the spectral resolution of WorldView-2 image (8 bands, 2 m pixel size). The spectral angle mapper (SAM) method was the used to locate and map the distribution of each targeted mangrove species. As expected, the results showed that the largest difference of spectral curves between species was at the NIR wavelength spectrum (700-900nm). Hence, it is potential to be used as the basis for identification of species mangrove from remote sensing imagery. However, the result of this mapping approach only showed a low accuracy of 62%. The low value of map accuracy was attributed to the inaccuracy in defining threshold in SAM for each class. This study provides a basic understanding of the use of spectral reflectance for mangrove species mapping from remote sensing imagery.
Characterization of seagrass spectral reflectance response is important to understand seagrass condition and for
the possibility of mapping activities using remote sensing data, which is important for the management,
monitoring, and evaluation of seagrass ecosystem. This paper presents the spectral reflectance response of
several tropical seagrass species. These species are Enhalus acoroides (Ea), Thalassia hemprichii (Th) and
Cymodocea rotundata (Cr). Spectral reflectance response of healthy seagrass, epiphyte-covered seagrass, and
damaged seagrass leaves for each species were measured using Jaz EL-350 field spectrometer ranged from 350 -
1100 nm. Repeated measurements were performed above water on harvested seagrass leaves. The results
indicate that there is a change in spectral reflectance response of damaged or epiphyte-covered seagrass leaves
compared to the healthy leaves. The results show similar pattern for the three species, where the peak
reflectance in visible wavelengths shifted toward longer wavelengths on damaged seagrass leaves. The results of
this research open up a possibility of mapping seagrass health condition using remote sensing image.
Effective mangrove management requires spatially explicit information of mangrove tree crown map as a basis for ecosystem diversity study and health assessment. Accuracy assessment is an integral part of any mapping activities to measure the effectiveness of the classification approach. In geographic object-based image analysis (GEOBIA) the assessment of the geometric accuracy (shape, symmetry and location) of the created image objects from image segmentation is required. In this study we used an explicit area-based accuracy assessment to measure the degree of similarity between the results of the classification and reference data from different aspects, including overall quality (OQ), user’s accuracy (UA), producer’s accuracy (PA) and overall accuracy (OA). We developed a rule set to delineate the mangrove tree crown using WorldView-2 pan-sharpened image. The reference map was obtained by visual delineation of the mangrove tree crowns boundaries form a very high-spatial resolution aerial photograph (7.5cm pixel size). Ten random points with a 10 m radius circular buffer were created to calculate the area-based accuracy assessment. The resulting circular polygons were used to clip both the classified image objects and reference map for area comparisons. In this case, the area-based accuracy assessment resulted 64% and 68% for the OQ and OA, respectively. The overall quality of the calculation results shows the class-related area accuracy; which is the area of correctly classified as tree crowns was 64% out of the total area of tree crowns. On the other hand, the overall accuracy of 68% was calculated as the percentage of all correctly classified classes (tree crowns and canopy gaps) in comparison to the total class area (an entire image). Overall, the area-based accuracy assessment was simple to implement and easy to interpret. It also shows explicitly the omission and commission error variations of object boundary delineation with colour coded polygons.
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