DIGITAL AERIAL IMAGES FOR COASTAL REMOTE SENSING APPLICATION Emmanuel Oppong Afriyie 1 , Vladimir Y. Mariano 2 , Donald A. Luna 3 1 Institute of Computer Science, University of the Philippines Los Banos, Philippines Email: oppongafriyie@gmail.com 2 Vladimir Y. Mariano, Centre of Technology, RMIT University Vietnam Email: vladimir.mariano@rmit.edu.vn 3 Donald A. Luna, Senior Science Research Specialist, Phil-LiDAR 2 UPLB, Philippines Email: lunadonald@gmail.com KEY WORDS: UAVs, Photogrammetric, Coastal Mapping ABSTRACT: Lately the use of Unmanned Aerial Vehicles (UAVs) for remote sensing has attracted attention from researchers. This can be attributed to its low cost and feasibility to automate flight commands along a set of waypoints. Moreover, UAVs has shown promise lately in a number of areas including monitoring vegetation and soil health, agriculture, forestry and land use. However, little is being done related to coastal management or aquatic monitoring. Most of the remote sensing researches attributed to coastal monitoring and management are usually satellite based or Compact Airborne Spectrographic Imager (CASI). UAVs can fly in place of piloted aircraft to gather remote sensing information on coastal area characteristics from mangroves to seagrass to corals. the UAV, it is possible to acquire video, aerial photographs, multispectral and hyperspectral radiometric, LiDAR, and radar data etc. This study utilizes UAV with a small digital camera for medium scale coastal mapping. The first objective of this study is to investigate the use of lightweight first person view (FPV) raptor UAV for mapped image of coastal body with limited ground control points for generating orthophoto mosaic of the coastal area. Aerial photographs were acquired at an estimated of 60% forward lap and 40% side lap specifications. The second objective is to determine the accuracy of the photogrammetric output. It is expected that this survey will provide guidelines for future remote sensing project using low cost digital aerial images. Also the results from this study will serve as an input for further analysis to identify submerged aquatic vegetation like seagrass. 1. INTRODUCTION Aerial photography is a powerful tool for identifying habitats within the photic zone. Aerial photography is well suited to deriving certain types of information about benthic habitats. In the near shore estuarine and marine environment, this zone can range from as shallow as two meters to as deep as 30 meters. In addition, aerial photography still remains as the primary source of optical remote sensing for most shallow marine resource management agencies as presented by Orth et al., 2004 and Lathrop et al., 2004. However, majority of aerial photography used for seabed mapping focused on assessing terrestrial landscapes, thus optimum conditions for shallow water mapping, including atmospheric and water column conditions are not considered much. Oftentimes, shallow water coverage often much of the shallow water coverage is of poor quality. Methods for acquiring vertical or nadir-looking aerial photography over shallow marine waters were first described by Lee (1922). Most photogrammetric literature focuses on broad scale mapping programs of the coastline and/or near shore bathymetry (Lillesand and Kiefer, 2000; Wolf and Dewitt, 2000). Recently, comprehensive manuals detailing methodologies for mapping seagrass habitats were produced by large agencies such as NOAA Coastal Services Center, The United Nations Educational, Scientific and Cultural Organization (UNESCO)and the Joint Nature Conservation Committee (JNCC) (e.g., Waddington and Hart, 2003). At the same time small format aerial photography (SFAP) has seen renewed interest and technique development (Phinn et al., 2001; Mills et al., 2003) as it is well suited to low cost, specialised remote sensing for resource management purposes that target limited areas, with a particular focus on temporal monitoring. The key developments taking place in aerial photography for habitat mapping in shallow coastal waters include: sensor advances and improved availability of small format digital cameras; development of image capture methods including a reduced need for ground control; improving image interpretation and analysis, such as object oriented classifications; and an increasing range of applications such as, fine-scale spatial metric studies. 2. IMAGE ACQUISITION AND PROCESSING 2.1 Image acquisitions An FPV raptor was used to gather all the images used in this study. The UAV shown in Figure 1A, and its technical specifications are presented in table 1.