Abstract
Mangroves have a lot of economic and ecological advantages which include coastal protection, habitat for wildlife, fisheries and forestry products. Determination of the extent of mangrove patches in the coastal areas of the Philippines is therefore important especially in resource conservation, protection and management. This starts with a well-defined and accurate map. LiDARwas used in the mangrove extraction in the different coastal areas of Negros Occidental in Western Visayas, Philippines. Total coastal study area is 1,082.55 km² for the 14 municipalities/ cities processed. Derivatives that were used in the extraction include, DSM, DTM, Hillshade, Intensity, Number of Returns and PCA. The RGB bands of the Orthographic photographs taken at the same time with the LiDAR data were also used as one of the layers during the processing. NDVI, GRVI and Hillshade using Canny Edge Layer were derived as well to produce an enhanced segmentation. Training and Validation points were collected through field validation and visual inspection using Stratified Random Sampling. The points were then used to feed the Support Vector Machine (SVM) based on tall structures. Only four classes were used, namely, Built-up, Mangroves, Other Trees and Sugarcane. Buffering and contextual editing were incorporated to reclassify the extracted mangroves. Overall accuracy assessment is at 98.73% (KIA of 98.24%) while overall accuracy assessment for Mangroves only is at 98.00%. Using this workflow, mangroves can already be extracted in a large-scale level with acceptable overall accuracy assessments.
Highlights
Mangrove forests are generally found in the coastal waters of tropical and subtropical countries between approximately 300 N and 300 S latitude (Giri et al, 2011)
Once Mangroves were extracted, they were inspected if they were correctly classified. This was done through buffering and contextual editing
Contextual editing was done using neighbourhood metrics to correctly classify additional features. Another overall accuracy assessment was done after contextual editing
Summary
Mangrove forests are generally found in the coastal waters of tropical and subtropical countries between approximately 300 N and 300 S latitude (Giri et al, 2011). These productive ecosystems are found in the intertidal zones and are very resilient to harsh environments such as drastic change in temperature, amount of rainfall, salinity and pH, among others. It is used as habitat for a variety of faunal organisms like birds, fish, crustaceans, shellfish, reptiles and mammals as well as juveniles of many commercial fish and invertebrates which utilize mangroves as nurseries. It is used as habitat for a variety of faunal organisms like birds, fish, crustaceans, shellfish, reptiles and mammals as well as juveniles of many commercial fish and invertebrates which utilize mangroves as nurseries. (Manson et al 2005)
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