Peter Gege's research while affiliated with German Aerospace Center (DLR) and other places
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Publications (163)
Spatial in-situ measurements of spectral remote sensing reflectance for the validation of optical satellite data over inland water bodies are usually carried out from boats or ships, where hull, superstructures and crew have an unknown influence on the results. Drift, caused by wind and currents, makes it impossible to stay precisely at the same po...
The development of algorithms for remote sensing of water quality (RSWQ) requires a large amount of in situ data to account for the bio-geo-optical diversity of inland and coastal waters. The GLObal Reflectance community dataset for Imaging and optical sensing of Aquatic environments (GLORIA) includes 7,572 curated hyperspectral remote sensing refl...
Peru is amongst the most affected countries by climate change in the world, with severe consequences on the availability of water across the country. The GIZ funded project "Multisectoral management of water resources in the Mantaro River basin" (ProGIRH) aims to improve the integrated and climate-sensitive water resource management in the Mantaro...
The many bands and the high spectral resolution of hyperspectral sensors such as PRISMA, DESIS or EnMAP appear very promising for phytoplankton classification, but their increased sensor noise compared to multispectral sensors imposes limitations on threshold concentrations and the number of phytoplankton groups that can be distinguished. An analyt...
Spectral measurements in aquatic remote sensing are usually carried out from ships, boats or stationary platforms. While the latter only covers a single location, mobile platforms can introduce significant errors due to unexpected movement (drift and rotation), reflection and shadowing effects from the ship’s hull, superstructures and the personnel...
The Landsat series has marked the history of Earth observation by performing the longest continuous imaging program from space. The recent Landsat-9 carrying Operational Land Imager 2 (OLI-2) captures a higher dynamic range than sensors aboard Landsat-8 or Sentinel-2 (14-bit vs. 12-bit) that can potentially push forward the frontiers of aquatic rem...
Phytoplankton play an important role in the aquatic biogeochemical cycling such as for the formation of organic matter by photosynthetic processes through the fixation of carbon dioxide, and assimilation of macro- and micronutrients depending on their metabolic needs. These processes are common to all phytoplankton, however some phytoplankton group...
The project MONEOWET focuses on multispectral and hyperspectral Earth Observation (EO) data to investigate water quality in relation to agricultural activities within the Térraba Sièrpe Wetland in Costa Rica. This study corresponds to an initiative focused on investigating the applicability of remote sensing data in tropical systems. The main topic...
Coastal and inland aquatic ecosystems are of fundamental interest for societal and economical purposes due to a significant part of the population living there. They both highly contribute to carbon cycling and biodiversity. Those ecosystems are continuously impacted by natural processes and human activities. Many of these impacts become more frequ...
The submerged harbors of Amathus in Cyprus and Hipponion in the South of Italy are examples of sensitive cultural heritage requiring special attention in the frame of Marine Spatial Planning. This paper introduces the use of the DESIS sensor, an imaging spectrometer mounted on the International Space Station, for the monitoring of cultural heritage...
The project "Application of multispectral and hyperspectral Earth Observation data to investigate water quality in relation to agricultural activities within the Térraba Sièrpe Wetland in Costa Rica - MONEO-WET)" corresponds to an initiative focused on investigating the applicability of remote sensing data in tropical systems. The main topic of thi...
The high spectral resolution of hyperspectral sensors is beneficial for distinguishing phytoplankton types, but the increased noise compared to multispectral land and ocean satellite sensors decreases the sensitivity to concentration changes. This study simulates for six water types (high/low concentrations of chl-a, CDOM and total suspended matter...
The DLR Earth Sensing Imaging Spectrometer (DESIS) is a space-based instrument installed and operated on the International Space Station (ISS). This space mission is the achievement of the collaboration between the German Aerospace Center (DLR) and the US company Teledyne Brown Engineering (TBE). DLR has developed the instrument and the software fo...
Satellite sensor configurations enabling high spatial and high spectral resolution could be far more suited for monitoring inland and coastal water ecosystems’ water quality than common ocean color sensors. It is expected that even the composition of phytoplankton, the primary producer in these ecosystems, could be determined. Up to now, atmospheri...
Different methods are available for retrieving chlorophyll-a (Chl-a) in inland waters from optical imagery, but there is still a need for an inter-comparison among the products. Such analysis can provide insights into the method selection, integration of products, and algorithm development. This work aims at inter-comparison and consistency analyse...
The submerged harbor of Amathus in Cyprus is a sensitive cultural heritage requiring special attention in the frame of Marine Spatial Planning. The monitoring of water depth in the surrounding area can raise awareness on effects, such as shoreline erosion, which could lead to a deterioration of the relics.
The DLR Earth Sensing Imaging Spectrometer (DESIS) is a space-based instrument installed on the International Space Station (ISS) and operating since September, 2018. It is a collaboration mission between the German Aerospace Center (DLR) responsible for the development of the instrument and the data processing software and the US company Teledyne...
This section provides a synthesis of water color applications in aquatic science. It describes traditional sampling methods based on eyesight, which are becoming increasingly popular in citizen science, and in combination with smart phone applications. On the other end, we present radiometric measurements with advanced opto-electronic sensors that...
The submission system is now open for reviewing original manuscripts in the context of remote sensing of inland and coastal waters:
https://www.mdpi.com/journal/remotesensing/special_issues/method_biophy_coast
The submerged harbor of Amathus in Cyprus is a sensitive cultural heritage requiring special attention in the frame of Marine Spatial Planning. The monitoring of water depth in the surrounding area can raise awareness on effects, such as shoreline erosion, which could lead to a deterioration of the relics. This paper assesses the quality of bathyme...
The recent PlanetScope constellation (130+ satellites currently in orbit) has shifted the high spatial resolution imaging into a new era by capturing the Earth’s landmass including inland waters on a daily basis. However, studies on the aquatic-oriented applications of PlanetScope imagery are very sparse, and extensive research is still required to...
This paper studies the measurement requirements of spectral resolution and radiometric sensitivity to enable the quantitative determination of water constituents and benthic parameters for the majority of optically deep and optically shallow waters on Earth. The spectral and radiometric variability is investigated by simulating remote sensing refle...
Laguna Lake, the Philippines’ largest freshwater lake, has always been historically, economically, and ecologically significant to the people living near it. However, as it lies at the center of urban development in Metro Manila, it suffers from water quality degradation. Water quality sampling by current field methods is not enough to assess the s...
Laguna Lake, the Philippines' largest freshwater lake, has always been historically, economically, and ecologically significant to the people living near it. However, as it lies at the center of urban development in Metro Manila, it suffers from water quality degradation. Water quality sampling by current field methods is not enough to assess the s...
Imaging spectrometry of non-oceanic aquatic ecosystems has been in development since the late 1980s when the first airborne hyperspectral sensors were deployed over lakes. Most water quality management applications were, however, developed using multispectral mid-spatial resolution satellites or coarse spatial resolution ocean colour satellites til...
Übersichtsvortrag über aktuelle Arbeiten und Ergebnisse am DLR Oberpfaffenhofen zur Fernerkundung von Binnengewässern
This study presents the work developed as a CEOS action for which CSIRO and DLR taken the lead on a feasibility assessment to determine the benefits and technological difficulties of designing an Earth observing satellite mission focused on the aquatic (non-oceanic) ecosystems. I n fact, many Earth observing sensors have been designed, built and la...
Operations in a military naval context require a detailed planning and information gathering. For this purpose, remote sensing is a useful technique without in-situ survey. A collaboration of Fraunhofer IOSB (Institute of Optronics, System Technologies and Image Exploitation), DLR (German Aerospace Center), and Bundeswehr Geoinformation Centre ZGeo...
Remote sensing and field spectroscopy of natural waters is typically performed under clear skies, low wind speeds and low solar zenith angles. Such measurements can also be made, in principle, under clouds and mixed skies using airborne or in-situ measurements; however, variable illumination conditions pose a challenge to data analysis. In the pres...
Tutorial on aquatic remote sensing Part I Introduction to aquatic remote sensing Part II Satellite data Part III Field and laboratory measurements
Improving the predictive capabilities for the development of Arctic sea ice cover strongly depends on a better understanding of the ice-albedo feedback mechanism. Using a combination of multi- and hyperspectral airborne imagery, field spectroscopy and bio-optical modelling we aim to quantify melt pond fraction, melt pond depth, thickness of underly...
The aquatic ecosystems of coastal and inland waters are more variable than the open ocean as water constituents and bottom substrates differ considerably in type, concentration and optical properties. Sensors with high spatial, spectral and radiometric resolution are therefore required to provide enough detail for mapping these highly complex envir...
Many Earth observing sensors have been designed, built and launched with primary objectives of either terrestrial or ocean remote sensing applications. Often the data from these sensors are also used for freshwater, estuarine and coastal water quality observations, bathymetry and benthic mapping. However, such land and ocean specific sensors are no...
Optical remote sensing of phytoplankton draws on distinctive spectral features which can vary with both species and environmental conditions. Here, we present a set-up (Envilab) for growing phytoplankton under well-defined light, temperature and nutrient conditions. The custom-built light source enables creation of light with spectral composition s...
The oceans are monitored since decades using multispectral sensors on satellite, but very little information is available for the majority of inland waters since they are too small for ocean colour satellites, optically too complex for most multispectral sensors and too numerous (around 120 million lakes > 15 m) for traditional sampling. Since inla...
Uncertainties of aerosol parameters are the limiting factor for atmospheric correction over inland and coastal waters. For validating remote sensing products from these optically complex and spatially inhomogeneous waters the spatial resolution of automated sun photometer networks like AERONET is too coarse and additional measurements on the test s...
Sky reflectance Rsky is used to correct in situ reflectance measurements in the remote detection of water color. We analyzed the directional and spectral variability in Rsky due to adjacency effects against an atmospheric radiance model. The analysis is based on one year of semi-continuous Rsky observations that were recorded in two azimuth directi...
A three-component reflectance model (3C) is applied to above-water radiometric measurements to derive remote-sensing reflectance Rrs (λ). 3C provides a spectrally resolved offset Δ(λ) to correct for residual sun and sky radiance (Rayleigh- and aerosol-scattered) reflections on the water surface that were not represented by sky radiance measurements...
Coral reefs, among the world's most biodiverse and productive submerged habitats, have faced several mass bleaching events due to climate change during the past 35 years. In the course of this century, global warming and ocean acidification are expected to cause corals to become increasingly rare on reef systems. This will result in a sharp decreas...
Coral reefs, among the world’s most biodiverse and productive submerged habitats, have faced several mass bleaching events due to climate change during the past 35 years. In the course of this century, global warming and ocean acidification are expected to cause corals to become increasingly rare on reef systems. This will result in a sharp decreas...
The inland waters on Earth are as manifold as their surrounding ecosystems and catchment areas: water constituents and sea floor composition differ considerably in type, concentration and optical properties. The associated optical diversity of pelagial and benthos makes the quantitative description of the observed spectral variety of inland waters...
The Committee on Earth Observation Satellites (CEOS) response to the Group on Earth Observations System of Systems (GEOSS) Water Strategy developed under the auspices of the Water Strategy Implementation Study Team was endorsed by CEOS at the 2015 Plenary. As one of the actions, CSIRO has taken the lead on recommendation C.10: A feasibility assessm...
Goal of this study is to derive sensor requirements for measuring the spectral and radiometric properties of different water and benthic cover types that are relevant for extracting information from optically deep and shallow inland, coastal and coral reef waters. For this purpose forward simulations of hyperspectral measurements are made. Using an...
Many Earth observing sensors have been designed, built and launched with primary objectives of either terrestrial or ocean remote sensing applications. Often the data from these sensors are also used for freshwater, estuarine and coastal water quality observations and bathymetry and benthic mapping. However, such land and ocean specific sensors are...
Satellite remote sensing may assist in meeting the needs of lake monitoring. In this study, we aim to evaluate the potential of Sentinel-2 to assess and monitor water constituents and bottom characteristics of lakes at spatio-temporal synoptic scales. In a field campaign at Lake Starnberg, Germany, we collected validation data concurrently to a Sen...
Specular reflections of the sun and the sky at the water surface (sunglint, skyglint) can be of comparable intensity or even much higher as the water leaving radiance, even for observation geometries minimizing the sunglint. A number of approaches have been developed for correcting these glint signals, practically all based on the near infrared spe...
The Calibration Home Base (CHB) is an optical laboratory designed for the calibration of imaging spectrometers for the VNIR/SWIR wavelength range. Radiometric, spectral and geometric calibration as well as the characterization of sensor signal dependency on polarization are realized in a precise and highly automated fashion. This allows to carry ou...
Poster for the Living Planet Symposium 2016 in Prague.
Atmospheric correction is a critical step and can be a limiting factor in the extraction of aquatic ecosystem parameters from remote sensing data of coastal and lake waters. Atmospheric correction models commonly in use for open ocean water and land surfaces can lead to large errors when applied to hyperspectral images taken from satellite or aircr...
The contribution of mineral-rich suspended matter (MSM) to the optics of water bodies is still less treated by bio-optical modeling than that of other water constituents. However, with the increasing number of remote sensing studies on inland waters, optical properties of terrestrial particles gain importance for accurately estimating particle conc...
With the advent of Sentinel-2A new, unprecedented opportunities emerged for analyzing lakes by remote sensing with respect to spatial, radiometric, spectral and temporal resolution. This study is based on a Sentinel-2A scene acquired at Lake Starnberg, an oligotrophic, peri-alpine lake. Atmospheric correction with Sen2Cor worked well showing, howev...
(English abstract below)
Kurzfassung
Optische Technologien und Verfahren sind sowohl in der limnischen als auch marinen Forschung Deutschlands über alle Bereiche und Skalen etabliert und entwickeln sich rasant weiter. Die Arbeitsgruppe „Aquatische Optische Technologien“ (AOT) will Forschern und Anwendern eine Plattform bieten, die Wissenstransfer...
This paper investigates at the example of bathymetry how much an application can profit from comprehensive
characterisations required for an improved calibration of data from a state-of-the-art commercial hyperspectral sensor. A NEO HySpex VNIR-1600 sensor is used for this study, and the improvements are based on measurements of sensor properties n...
The European collaborative project GLaSS aims to prepare for the use of the data streams from Sentinel 2 and Sentinel 3. Its focus is on inland waters, since these are considered to be sentinels for land-use- and climate change and need to be monitored closely. One of the objectives of the project is to compare existing water quality algorithms and...
An image processing software is presented which allows quantitative analysis of multi- and hyperspectral data from oceanic, coastal and inland waters. The usage of the software is demonstrated at the example of bathymetry.
We present the Airborne Prism Experiment (APEX), its calibration and subsequent radiometric measurements as well as Earth science applications derived from this data. APEX is a dispersive pushbroom imaging spectrometer covering the solar reflected wavelength range between 372 and 2540 nm with nominal 312 (max. 532) spectral bands. APEX is calibrate...
We present the Airborne Prism Experiment (APEX), its calibration and subsequent radiometric measurements as well as Earth science applications derived from this data. APEX is a dispersive pushbroom imaging spectrometer covering the solar reflected wavelength range between 372 and 2540 nm with nominal 312 (max. 532) spectral bands. APEX is calibrate...
Optische Technologien und Verfahren sind sowohl in der limnischen als auch marinen Forschung Deutschlands über alle Bereiche und Skalen etabliert und entwickeln sich rasant weiter. Die Arbeitsgruppe „Aquatische Optische Technologien“ (AOT) will Forschern und Anwendern eine Plattform bieten, die Wissenstransfer fördert, der nationalen Entwicklergeme...
The GlaSS consortium has an excellent working knowledge on how to apply MERIS RR and The GlaSS consortium has an excellent working knowledge on how to apply MERIS RR and The GlaSS consortium has an excellent working knowledge on how to apply MERIS RR and The GlaSS consortium has an excellent working knowledge on how to apply MERIS RR and The GlaSS...
In coastal regions, hyperspectral remote sensing is becoming an established method to map water depth. For inland waters however, only few studies based on empirical methods have been published so far. This paper presents a study for the German lake Starnberger See using a physically based approach. Hyperspectral data were acquired from airplane us...
An image processing software has been developed which allows quantitative analysis of multi- and hyperspectral data from oceanic, coastal and inland waters. It has been implemented into the Water Colour Simulator WASI, which is a tool for the simulation and analysis of optical properties and light field parameters of deep and shallow waters. The ne...
The standard procedure for wavelength calibration of monochromators in the visible and near infrared wavelength range uses low-pressure gas discharge lamps with spectrally well-known emission lines as primary wavelength standard. The calibration of a monochromator in the wavelength range of 350 to 2500 nm usually takes some days due to the huge
num...
As it can strongly influence the availability of light and thus primary production, coloured dissolved organic matter (CDOM) affects the function of lake ecosystems. Therefore reliable methods are required for the monitoring of CDOM concentration. A new method using downwelling irradiance was tested for applicability in four selected lakes of the B...
As it can strongly influence the availability of light and thus primary
production, coloured dissolved organic matter (CDOM) affects the
function of lake ecosystems. Therefore reliable methods are required for
the monitoring of CDOM concentration. A new method using downwelling
irradiance was tested for applicability in four selected lakes of the
B...
The German Aerospace Centre (DLR) is operating the Calibration Home Base (CHB) as a facility for the radiometric calibration of airborne hyperspectral sensors and field spectrometers, the calibration concept relying on the application of both absolutely calibrated source- and detector-based radiometric transfer standards. Following this concept, DL...
Blooms of harmful cyanobacteria have been shown to increase in both frequency and severity due to global warming, particularly through increased nutrient loads at extreme weather events with elevated winter/spring rainfall and flushing events followed by extended periods of summer drought. These blooms threaten our shrinking freshwater resources in...
This paper proposes a novel algorithm for the recovery of noisy bands from hyperspec-tral images. The method, based on spectral unmixing, relies on the spectral behavior of the materi-als on ground composing each image element. Firstly, reference spectra related to the classes of in-terest are used to perform spectral unmixing: these exhibit neglig...
A dedicated calibration technique was applied for the calibration of the spectral radiance transfer standard (RASTA) of the German Aerospace Center (DLR) at the Physikalisch-Technische Bundesanstalt (PTB), consisting of two independent but complementing calibration procedures to provide redundancy and smallest possible calibration
uncertainties. P...
The downwelling irradiance in water usually shows very high short-time variability due to focusing and
defocusing of the sun and sky light by the wave-modulated water surface. Since the direct and diffuse components are
affected differently by wave focusing, not only intensity is highly variable, but also the spectral shape is fluctuating. A
depth...
A software tool is presented which allows quantitative data analysis of optical remote sensing data from oceanic, coastal and inland waters. It can be easily adapted by the user to different sensors and to optical properties of the studied area. The software can import atmospherically corrected images from multi- and hyperspectral sensors in a numb...
The downwelling irradiance spectrum is so far not used directly for the determination of water constituents, mainly due to the large and unpredictable fluctuations of the underwater light field induced by the water surface. The potential of a new analytical model, which can cope with such environmental influences, was analyzed for the estimation of...
The downwelling irradiance is rarely utilized to determine optical parameters of a water body since the ever-changing water surface induces strong signal fluctuations in the upper meters of typically 20 to 40 %. An analytic model has been developed that calculates the spectra of the direct and diffuse component separately. It can cope with the fluc...