Comparison of Multispectral Satellite Imagery, AUV, and Geotagging Photos for Mapping Proposed Seagrass Restoration Areas Muhammad Banda Selamat (a*), Rohani Ambo-Rappe (a), Andi Muh. Agung Pratama (b)
a) Marine Sciences, Universitas Hasanuddin
Jalan Perintis Kemerdekaan km 10, Makassar 90242, Indonesia
*mbandaselamat[at]unhas.ac.id
b) Graduate Student of Marine Science Study Program
Abstract
Seagrass beds are plant communities that have adapted to the depths of shallow seawater near the coast. Seagrass communities are believed to play a significant role in the global carbon cycle, their presence in nearshore shallow water areas must be properly inventoried and monitored. The purpose of this research is to compare the level of detail of object recognition from georeferenced mapping technology in determining the location of seagrass beds that need to be restored. AUV photos were taken in shallow water near the coast of Badi Island and have been processed using photogrammetric software. This process created a cloud of pixels in virtual 3D space, allowing it to provide a topographic map of the study area. Furthermore, orthomosaic maps using stitching techniques were created, displaying shallow water landforms near the coast and various types of substrates. In comparison, a large number of geotagged photos were collected at the study site. The elapse time technique was used to photograph benthic substrates at 5 second intervals following the bathymetric tracking lane. The photos are then georeferenced using a time reference from a simultaneously operating mapsonder GNSS. The comparison shows that orthomosaic maps and Sentinel 2 imagery both have advantages in terms of generating synoptic information, however the spatial resolution of the AUV orthomosaic map outperforms Sentinel 2 satellite imagery significantly. In terms of detailed recognition of mapped benthic objects, photo geotagging techniques exceed orthomosaic maps and Sentinel 2 imagery. This study indicates that geotagging techniques must be used in conjunction with AUV-based mapping technology when seagrass restoration sites require preliminary information on existing seagrass species.
