THE LATEST BATHYMETRY AND TOPOGRAPHY EXTRACTION OF LAKE LEDULU FROM MULTI-SOURCE GEOSPATIAL DATA

Atriyon JULZARIKA , Dany Puguh LAKSONO , Luki SUBEHI , Elisa ISWANDONO , Alfred Onisimus Maximus DIMA , Media Fitri Isma NUGRAHA , Kayat KAYAT

DOI: 10.21163/GT_2023.182.14

ABSTRACT: Topography is the basic geospatial information that is used as the main reference in the extraction of thematic geospatial information. It consists of terrestrial topography (topography) and underwater topography (bathymetry). One of the problems related to topography is the availability of detailed and up-to-date topographic and bathymetry data. This research proposes the latest bathymetry and topography extraction modeling with multi-source geospatial data including PlanetScope, Sentinel-1, Landsat images, and in-situ field data. The study area is located in Lake Ledulu, Rote Island, Indonesia. Bathymetry and topography were extracted using PlanetScope imagery and in-situ field data using the least squares adjustment computation approach. The mathematical design model uses the latest DTM method, which correlated with in-situ data. Time-series Landsat and PlanetScope are used to extract the lake bank boundaries with water using the harmonic method. DEM integration method is used to integrate bathymetry and topography. The updated topography and bathymetry are performed by adding the true vertical deformation extracted from Sentinel-1 imagery using the D-InSAR method. The results obtained are the latest bathymetry and topography of Lake Ledulu in 2022 or so-called DTM (2022). Then DTM (2022) is tested for profile checking and vertical accuracy at the confidence level of 95 % according to the ASPRS 2014. The DTM (2022) of Lake Ledulu has a vertical accuracy of + 61.54 cm or according to 1:5000 – 1:10000 scale mapping. DTM (2022) is also used to determine the dynamics of the volume of Lake Ledulu and its changes from 1985 to 2022. In 2022 (dry season) Lake Ledulu has a surface area (0.0946 km²), volume (701,688.45 m³), and perimeter (1.868 km). In 2022 (wet season), Lake Ledulu has a surface area (0.1555 km²), volume (1,116,525.9 m³), and perimeter (2.612 km). In 1985 (wet season) Lake Ledulu have surface area (0.3079 km²), volume (4,772,567.2 m³), and perimeter (3.477 km). The change in the surface area of Lake Ledulu from 1985-2022 was 0.1525 km² (decrease of 49.53%). The volume of Lake Ledulu from 1985-2022 was 3,656,041.3 m³ (decrease of 75.61%). Change in the perimeter of Lake Ledulu 1985-2022 was 0.862 km (shrinkage of 24.79%).

Keywords: Bathymetry, Topography, Lake Ledulu, Dynamics Volume, Multi-Source Geospatial Data

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