EnMAP Coral Reef Simulation – The first of its kind

The GFZ German Research Center for Geosciences and HySpeed Computing announce the first ever simulation of a coral reef scene using the EnMAP End-to-End Simulation tool. This synthetic, yet realistic, scene of French Frigate Shoals will be used to help test marine and coral reef related analysis capabilities of the forthcoming EnMAP hyperspectral satellite mission.

EeteS EnMAP Simulation FFS

EeteS simulation of EnMAP scene for French Frigate Shoals, Hawaii

EnMAP (Environmental Mapping and Analysis Program) is a German hyperspectral satellite mission scheduled for launch in 2017. As part of the satellite’s development, the EnMAP End-to-End Simulation tool (EeteS) was created at GFZ to provide accurate simulation of the entire image generation, calibration and processing chain. EeteS is also being used to assist with overall system design, the optimization of fundamental instrument parameters, and the development and evaluation of data pre-processing and scientific-exploitation algorithms.

EeteS has previously been utilized to simulate various terrestrial scenes, such as agriculture and forest areas, but until now had not previously been used for generating a coral reef scene. Considering the economic and ecologic importance of coral reef ecosystems, the ability to refine existing analysis tools and develop new algorithms prior to launch is a critical step towards efficiently implementing new reef remote sensing capabilities once EnMAP is operational.

The input imagery for the French Frigate Shoals simulation was derived from a mosaic of four AVIRIS flightlines, acquired in April 2000 as part of an airborne hyperspectral survey of the Northwestern Hawaiian Islands by NASA’s Jet Propulsion Laboratory. Selection of this study area was based in part on the availability of this data, and in part due to the size of the atoll, which more than adequately fills the full 30 km width of an EnMAP swath. In addition to flightline mosaicking, image pre-processing included atmospheric and geographic corrections, generating a land/cloud mask, and minimizing the impact of sunglint. The final AVIRIS mosaic was provided as a single integrated scene of at-surface reflectance.

For the EeteS simulation, the first step was to transform this AVIRIS mosaic into raw EnMAP data using a series of forward processing steps that model atmospheric conditions and account for spatial, spectral, and radiometric differences between the two sensors. The software then simulates the full EnMAP image processing chain, including onboard calibration, atmospheric correction and orthorectification modules to ultimately produce geocoded at-surface reflectance.

The resulting scene visually appears to be an exact replica of the original AVIRIS mosaic, but more importantly now emulates the spatial and spectral characteristics of the new EnMAP sensor. The next step is for researchers to explore how different hyperspectral algorithms can be used to derive valuable environmental information from this data.

For more information on EnMAP and EeteS: http://www.enmap.org/

EeteS image processing and above description performed with contributions from Drs. Karl Segl and Christian Rogass (GFZ German Research Center for Geosciences).

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