International Journal of Remote Sensing and Earth Sciences Vol. 19 No. 2 2022: 101–118 101 PLATFORM REEF LAGOON DETECTION FROM SENTINEL-2 IN PANGGANG ISLAND AND SEMAKDAUN ISLAND, SERIBU ARCHIPELAGO, JAKARTA Wikanti Asriningrum 1 , Azura Ulfa 1 , Kholifatul Aziz 2 , Kuncoro T. Setiawan 1 , Dyah Pangastuti 3 1 Research Center for Remote Sensing, National Research and Innovation Agency (BRIN) 2 Center for Data and Information, National Research and Innovation Agency (BRIN) 3 Center for Mapping Marine and Coastal Environments, BIG e-mail: azur001@brin.go.id Received: 29.10.2022; Revised: 31.12.2022; Approved: 31.12.2022 Abstract. Processing of satellite image data for the detection of platform reef lagoons is intended as one of the geo-physical parameters of the reef landform. Panggang Island and Semakdaun Island, Seribu Archipelago, Jakarta were chosen to make the detection model because they are ideal for lagoon reef landforms and tapulang court reefs. This model is only valid in the continental shelf area and the back arc and small island tectonic type. Determination of this location is done to improve the accuracy of spectral-based data processing. Platform reefs are one of four classes of reef landforms. Sentinel-2A data with a spatial resolution of 10m, blue, green, red, and near infrared bands were selected to investigate their ability to detect lagoons. Processing of data by calculating the Optimum Index Factor (OIF) to produce a composite image and drawing transect lines to produce pixel values and spectral graphics of the lagoon. The results of data processing in the form of graphs, composite images and pixel values were built to realize a digital lagoon detection model. These results are used for lagoon growth stage analysis for the classification of three platform reef landforms, visually and digitally interpretation. This digital and visual detection system design is useful for monitoring coral reef ecosystems. Keywords: Lagoon, platform reef, remote sensing, spectral, coral reef 1 INTRODUCTION Coral reefs are being degraded worldwide (Bellwood et al., 2004). 19% of coral reefs are lost and 75% are threatened in 2011 (Burke et al., 2012) due to threats from natural conditions (CO2 levels increased through global warming and ocean acidification) and anthropogenic (coastal development, overexploitation, overfishing and damaging, and waste) on a regional and global scale (Wilkinson, et al., 2008). This makes reef lagoon detection modeling for landform classification important in order to assess the impact of disturbances and efforts to restore/reduce degradation Reefs are a landform that built from coral and calcareous algae. Reef landforms are grouped into 3, namely fringing reefs, barrier reefs and atolls (Selby, 1985). While Maxwell, (1968) referred to Zuidam, (1985), the three groups are called oceanic reefs and there are other groups of shelf reefs. The Faculty of Geography UGM and Bakosurtanal in 2000 adopted the Maxwell classification, which includes the classification of landforms of organic origin. This classification is based on the origin of the formation (genesis) of landforms using relief/topography parameters, geological/rock structures, geomorphological processes, and the level of geomorphological processes acting on the landform(Table 2-1). The balance of the direction of organic landform development is controlled by hydrological, bathymetric, and biological factors. The balance of these three factors will produce a lagoonal platform reef, but if it is influenced by bathymetry, it forms an elongated platform reef (Asriningrum, 2009). The platform reef is one of the four classes of landforms and is the focus of this study. Lagoon are marine waters that form inside reefs. Areas within the lagoon have high productivity in the fisheries sector (Anthony et al., 2009). The lagoon is a source of community livelihood and as a provider of ecosystem resources and services, so that the lagoon can be used as a complex socio-ecological system for life in nature (Newton et al., 2014). The