Satellite Altimetry in South-West Bass Strait
1CSIRO, Climate Science Center, Australia; 2University of Tasmania, Australia
In this presentation we will detail our study area for improved understanding of coastal/SAR altimetry in the south west part of Bass Strait, Australia. This area hosts an absolute in situ calibration facility for the Jason-series satellite altimeters, having commenced operation in 1992 following the launch of TOPEX/Poseidon. In view of the new and upcoming SAR and InSAR satellite altimeters (Jason-CS/Sentinel-6, Sentinel-3A, Sentinel-3B and SWOT) we are expanding activity to capture data at multiple in situ comparison points that include our historical nadir altimetry comparison point, as well as two cross overs for the Sentinel-3A and 3B mission. We have developed an observation strategy that includes in situ equipment (pressure gauges, current meters and 3D wind/wave ADCPs, GNSS equipped buoys) complemented by a high resolution ocean model in order to deliver quality calibration and validation of satellite observations. While expanding the study area, we are able to interpret and validate measurements from the various satellite instruments (LRM, SAR, and in the future, InSAR). After presenting our cal/val system developments, we will show the updated results for the Jason series as well as case studies on early measurements by Sentinel-3A and Jason-3. In particular, we will illustrate the benefit of the SAR mode onboard Sentinel-3 in this area were numerous islands and challenging coastline make classical nadir radar altimetry more challenging close to the coast.
Validation of Sentinel-3A Altimetry Data by Using In-Situ Multi-Platform Observations near Mallorca Island (Western Mediterranean)
1IMEDEA (CSIC-UIB), Balearic Islands, Spain; 2SOCIB, Balearic Islands, Spain; 3CLS, Toulouse, France
In the frame of the Copernicus Marine Environment Monitoring Service (CMEMS) Sea Level Thematic Assembly Center (SL-TAC), a glider mission was undertaken between May and June 2016 along the same track as the overpass of the Sentinel 3A satellite in the Southern Mallorca region. Moreover, a one-day ship mission on May 30, synchronous with the overpass of the satellite, captured two transects of moving vessel ADCP close to the coastal area. The aim was to compare the along track altimeter products and multi-platform in-situ observations in the southern coastal zone of the Mallorca Island and the Algerian Basin. In addition, we explored the potential of the Synthetic Aperture Radar Mode (SARM) instrumentation of Sentinel-3 mission, which enables the satellite to measure nearest the coasts with both higher spatial resolution and higher precision than previous missions. With the ultimate goal of contributing to a more complete understanding of both ocean and coastal physical processes and the biogeochemical impacts.
The analyses presented here are conducted through the comparison of Absolute Dynamic Topography (ADT) obtained from the Sentinel-3A altimetry measurements along ground-track #713 and Dynamic Heights (DH) derived from temperature and salinity profiles measured by the glider along the trajectory followed by the satellite. Moreover, currents derived from altimetry and in-situ glider data along the track followed by the satellite; and from ADCP data collected in the coastal region are analysed. Results show a good agreement between ADT from altimetry and DH from glider data with maximum differences lower than 3 cm that promote a root mean square error of 2.08 cm. The correlation coefficient between both datasets is 0.85. As a consequence, satellite data strongly resembles the geostrophic velocity pattern observed by the glider measurements along the Algerian Basin and also by the ADCP data in the coastal zone.
This mission is part of a study focused on mesoscale variability and comparison of the along-track and gridded interpolated maps altimetry products in the western Mediterranean Sea using in-situ data including Argo, ADCP, gliders, drifters, HF radar and tide gauges data. We also take advantage of both the high spatial resolution and the region covered by these datasets to investigate the variability of physical processes in the coastal area. This experiment also contributes to the preparatory cal/val activities of the forthcoming wide-swath satellite altimeter (SWOT) that will provide daily high resolution sea surface height measurements during the fast phase after launch around the Balearic Islands.
A Novel Method for Lakes Water Level Measurement from SAR-SARIN Mode Altimetry – SHAPE Project
1ALONG-TRACK SAS, France; 2IsardSAT, UK; 3Univ. Porto, Portugal; 4SMHI, Sweden; 5Deimos/ESRIN, Italy; 6Serco/ESRIN, Italy; 7ESA/ESRIN, Italy
This work is part of the SEOM Sentinel-3 Hydrologic Altimetry Processor prototypE (SHAPE) study which aims at boosting the use of “SAR” mode altimetry data in hydrology. Meanwhile real Sentinel-3A data are available, the project focuses onto the use of CryoSat-2 data and try to mimic them as much as possible. While the study deals with both river and lake water height measurements, the work presented here is focused on medium to large size lakes.
One important challenge regarding the use of SAR mode data from CryoSat-2 is to estimate the local geoid from measurements which are spread aver the lake surface due to the space-time coverage of the geodetic orbit of the mission.
A novel methodology for the production of multi-mission water level time series is defined and employed. Various processing steps are impacted among which :
- for each lake crossing (coastline to coastline) water level measurements of consecutive records are combined together in a moving average filter to smooth out the noise component coming, for example, from windstress effects on lake surface. A water mask is used to constrain, in space, the domain of application of the moving average filters ;
- The geodetic orbit of CryoSat-2 is exploited in order to address tracks inter-calibration.
- The water elevation measurements, w.r.t. the ellipsoid model, obtained with this method are locally averaged within a given time interval and geobox to produce a mean lake surface impacted by the local geoid.
- Optionally, the production of time series can be done via what we call the "migration of CryoSat-2 measurements over the lake mean surface" for the period of interest
- The time series are then assessed via a standard validation procedure. In the end, validation results in SAR mode against in situ data are presented for lake Vänern ; a medium size lake but the largest one in Europe.
- We then discuss the choices of the space and time windows at several stages of the process. We also discuss the potential of this approach that eases and partially automates the production of lake water heights time series from CryoSat-2. In the end we discuss the integration with LRM and multi-mission time series over lakes.
Broadview Radar Altimetry Toolbox
1isardSAT Ltd., United Kingdom; 2DEIMOS Engenharia, Portugal; 3TU Delft, Faculty of Aerospace Engineering, The Netherlands; 4Deimos/ ESRIN , Italy; 5Serco / ESRIN , Italy; 6ESA / ESRIN, Italy
The universal altimetry toolbox, BRAT (Broadview Radar Altimetry Toolbox) which can read all previous and current altimetry missions’ data, incorporates now the capability to read the upcoming Sentinel-3 L1 and L2 products.
ESA endeavoured to develop and supply this capability to support the users of the future Sentinel-3 SAR Altimetry Mission. BRAT is a collection of tools and tutorial documents designed to facilitate the processing of radar altimetry data.
This project started in 2005 from the joint efforts of ESA (European Space Agency) and CNES (Centre National d’Etudes Spatiales), and it is freely available at http://earth.esa.int/brat. The tools enable users to interact with the most common altimetry data formats. The BratGUI is the front-end for the powerful command line tools that are part of the BRAT suite. BRAT can also be used in conjunction with MATLAB/IDL (via reading routines) or in C/C++/Fortran via a programming API, allowing the user to obtain desired data, bypassing the data-formatting hassle. BRAT can be used simply to visualise data quickly, or to translate the data into other formats such as NetCDF, ASCII text files, KML (Google Earth) and raster images (JPEG, PNG, etc.). Several kinds of computations can be done within BRAT involving combinations of data fields that the user can save for posterior reuse or using the already embedded formulas that include the standard oceanographic altimetry formulas.
The Radar Altimeter Tutorial, that contains a strong introduction to altimetry, shows its applications in different fields such as Oceanography, Cryosphere, Geodesy, Hydrology among others. Included are also “use cases”, with step-by-step examples, on how to use the toolbox in the different contexts. The Sentinel-3 SAR Altimetry Toolbox shall benefit from the current BRAT version. While developing the toolbox we will revamp of the Graphical User Interface and provide, among other enhancements, support for reading the upcoming S3 datasets and specific “use-cases” for SAR altimetry in order to train the users and make them aware of the great potential of SAR altimetry for coastal and inland applications. As for any open source framework, contributions from users having developed their own functions are welcome.
The Broadview Radar Altimetry Toolbox is a continuation of the Basic Radar Altimetry Toolbox. While developing the new toolbox we will revamp of the Graphical User Interface and provide, among other enhancements, support for reading the upcoming S3 datasets and specific “use-cases” for SAR altimetry in order to train the users and make them aware of the great potential of SAR altimetry for coastal and inland applications. As for any open source framework, contributions from users having developed their own functions are welcome.
The first Release of the new Radar Altimetry Toolbox was published in September 2015. It incorporates the capability to read S3 products as well as the new CryoSat-2 Baseline C.
The second Release of the Toolbox, in September 2016, will have a new graphical user interface and other visualisation improvements.
Evaluating the Performance of Sentinel-3 SRAL SAR Altimetry in the Coastal Zone, and Developing Improved Retrieval Methods. Early Results from the SCOOP Project.
1Satellite Oceanographic Consultants Ltd, United Kingdom; 2CLS, France; 3isardSAT, Catalonia; 4National Oceanography Centre, NERC, UK; 5Noveltis, France; 6University of Bonn, Germany; 7Delft University of Technology, The Netherlands; 8University of Porto, Portugal; 9SERCO/ESRIN, Italy; 10DEIMOS/ESRIN, Italy; 11ESA_ESRIN, Italy
SAR (or Delay Doppler) mode altimetry is expected to be particularly advantageous in the coastal zone, due to the much higher along-track resolution and the better signal to noise ratio provided in this mode, and this has been confirmed in recent years by analysis of CryoSat-2 data.
SCOOP (SAR Altimetry Coastal & Open Ocean Performance) is a project funded under the ESA SEOM (Scientific Exploitation of Operational Missions) Programme Element, started in September 2015, to characterise the expected performance of Sentinel-3 SRAL SAR mode altimeter products, in the coastal zone and open-ocean, and then to develop and evaluate enhancements to the baseline processing scheme in terms of improvements to ocean measurements. There is also a work package to develop and evaluate an improved Wet Troposphere correction for Sentinel-3.
This presentation will provide an overview of the SCOOP project, and present results of an analysis on the expected performance of the Sentinel-3 SRAL SAR mode products in the coastal zone, before considering possible modifications to the processing scheme that could enhance performance in the coastal zone. These potential enhancements include modifications both in the Delay Doppler Processing stage (L1A to L1B) and in the development and application of new waveform re-trackers (L1B to L2) designed to optimise performance in the coastal zone.
X-TRACK Regional Altimeter Products for Coastal Applications: 2016 release
1CTOH/LEGOS, France; 2Meudon Observatory, France
X-TRACK, has been developed by CTOH (Center of Topography of the Ocean and Hydrosphere) and LEGOS (Laboratoire d'Etudes en Géophysique et Hydrologie Spatiale) in order to optimize the completeness and the accuracy of the sea surface height information derived from satellite altimetry in coastal ocean areas. It is tailored for extending the use of altimetry data to coastal ocean applications and provides freely available along-track Sea Level Anomaly time series that cover today all the coastal oceans.
X-TRACK code was entirely rewritten in 2015/2016 in order to gain consistency and efficiency in the data processing workflow. We also revisited several aspects of the processing, as the altimetry corrections or the data editing strategy which has been significantly improved in order to obtain a better data quality for the points closest to the coast. We present here the new developments made in version 2016 of X-TRACK and the resulting improvement in terms of near-coastal sea level data availability and accuracy. Comparisons with the previous release of X-TRACK, with AVISO data and in-situ measurements are also shown. Discussions on the resulting cross-track surface geostrophic currents are also included.
Once more, the editing strategy will be now completely revised in order to systematically extend X-TRACK products to high-sampling rate SLA data depending on the altimeter mission (10 or 40 Hz). It should further improve the resolution of altimeter sea level observations near the coasts.
A New Era of Altimeter Products Towards High-Resolution
1CLS, France; 2CNES, France
The Sea-Level Thematic Assembly Center (SL-TAC) of the European Copernicus Marine Environment Marine Service (formerly known as DUACS/AVISO) currently ingests altimeter L2P products from 4 nadir missions: Jason-2, SARAL, Cryosat-2, HY-2A. The along-track spatial resolution of these missions is limited by the Low Resolution Mode (LRM) altimeter technology, except for SARAL whose performances are really higher. Current algorithms of the SL TAC provide operationally altimeter products with a spatial resolution about 200km and 14 days for the grids (L4) and locally 100km for the along-track products (L3).
In 2016, a new operational mission, Sentinel 3-A, has been launched. It is globally operated in the so-called Synthetic Aperture Radar Mode (SARM, or Delay-Doppler). CNES and ESA have used the regional SARM patches Cryosat-2 to demonstrate the possibility to gain in precision and resolution, typically up to 50km along-track. In parallel, the new operational Copernicus missions (Jason-3 then Jason-CS, Sentinel-3A/B) are going to increase the cross-track and temporal resolution of the altimeter constellation.
Through the development of new mapping techniques, the use of SARM missions and improvement of LRM processing, particularly with the SARAL mission, CNES and CLS work today on the development of a new higher resolution altimeter product (100 km / 7 days) to better serve environmental applications in regional and coastal regions. This paper will present a first status of this ongoing work.
Sentinel-3 Surface Topography Mission: Overview and Status of Operations
1ESA ESRIN, Italy; 2EUMETSAT, Germany; 3CLS, Toulouse; 4PML, UK; 5GMV, Spain; 6CNES, France
The Copernicus Programme, being Europe’s Earth Observation and Monitoring Programme led by the European Union, aims to provide, on a sustainable basis, reliable and timely services related to environmental and security issues. The Sentinel-3 mission forms part of the Copernicus Space Component. Its main objectives, building on the heritage and experience of the European Space Agency’s (ESA) ERS and ENVISAT missions, are to measure sea-surface topography, sea- and land-surface temperature and ocean- and land-surface colour in support of ocean forecasting systems, and for environmental and climate monitoring. The series of Sentinel-3 satellites will ensure global, frequent and near-real time ocean, ice and land monitoring, with the provision of observation data in a routine, long-term (up to 20 years of operations) and continuous fashion, with a consistent quality and a high level of reliability and availability.
The Sentinel-3 mission is jointly operated by ESA and EUMETSAT. ESA is responsible for the operations, maintenance and evolution of the Sentinel-3 ground segment on land related products and EUMETSAT for the marine products. All ground segment facilities supporting the Sentinel-3 operations have been operated over the last months and the science products qualified and assessed by the Mission Performance Framework team.
The Sentinel-3 Mission Performance Framework (MPF) has been established by ESA and EUMETSAT to ensure, over the mission lifetime, the required operability and fitness-for-purpose of the core science products generated by the Payload Data Ground Segment (PDGS) and delivered to the Copernicus Services and the science community.
The Sentinel-3 Mission Performance Framework embraces ESA and EUMETSAT ‘in-house’ expertise and experts as well as the Mission Performance Centre (MPC) Team, the Sentinel-3 Validation Team (S3VT), the Copernicus POD service and the CNES team.
This paper will provide an update on the status of the ground segment operations for the Sentinel-3 Topography Mission since launch, including results on the S-3 mission PDGS Altimetry products quality, Cal/Val results as well as early plans related to the upgrade of the Instrument Processing Facilities.
GOCE User Toolbox and Tutorial
1Technical University of Denmark, DTU Space; 2Deimos/ESRIN; 3SERCO c/o European Space Agency, Italy; 4ESA-ESRIN
The GOCE User Toolbox GUT is a compilation of tools for the utilisation and analysis of GOCE Level 2 products.
GUT support applications in Geodesy, Oceanography and Solid Earth Physics. The GUT Tutorial provides information
and guidance in how to use the toolbox for a variety of
applications. GUT consists of a series of advanced
computer routines that carry out the required computations. It may be used on Windows PCs, UNIX/Linux Workstations,
and Mac. The toolbox is supported by The GUT Algorithm Description and User Guide and The GUT
Install Guide. A set of a-priori data and models are made available as well. Without any doubt the development
of the GOCE user toolbox have played a major role in paving the way to successful use of the GOCE data for
oceanography. The GUT version 2.2 was released in April 2014 and beside some bug-fixes it adds the capability for the computation of Simple Bouguer Anomaly (Solid-Earth). During this fall a new GUT version 3 has been released. GUTv3 was further developed through a collaborative effort where the scientific communities participate aiming
on an implementation of
remaining functionalities facilitating a wider span of research in the fields of Geodesy,
Oceanography and Solid earth studies.
Accordingly, the GUT version 3 has:
An attractive and easy to use Graphic User Interface (GUI) for the toolbox,
Enhance the toolbox with some further software functionalities such as to facilitate the use of gradients,
anisotropic diffusive filtering and computation of Bouguer and isostatic gravity anomalies.
An associated GUT VCM tool for analyzing the GOCE variance covariance matrices.
A Synergy Approach for the Validation of Coastal Altimetry Data in the Baltic Sea
1Tallinn University of Technology, Estonia; 2Estonian Academy of Sciences
The introduction of SAR altimetry, now allows satellite altimetry data products to be available with a higher spatial resolution and precision that was previously not available in coastal and shelf sea areas. It is expected however that the satellite altimetry data products available will still be affected by some inaccuracies that are most likely due to land contamination and inadequate corrections applied (e.g. instrumental, atmospheric, geophysical) and possibly other sources. Thus validation on the reliability and accuracy of the data is necessary in order to establish certainty and confidence especially in complex sea areas such as the Baltic Sea (surrounded by different land masses and extensive archipelago regions). In this study a case study is performed for the Gulf of Finland (eastern Baltic Sea) whereby a validation of satellite altimetry data is performed for the sea level and currents data products. This validation consists of a statistical analysis that employs the synergy of satellite data (altimetry, ocean colour and surface temperature data) along with available in-situ (water level gauges, current meters and surface current drifters) and various model data. For reasonable error estimates of the combined data set a synergy of all the data is applied for given applications. Whist for high error estimates careful examination using statistical techniques into the possible sources and solutions of usage is illustrated.
Improved Sea Surface Height from Satellite Altimetry in Coastal Zones: A Case Study in Southern Patagonia
1Departamento de Ciencias de la Atmósfera y los Océanos (DCAO/FCEN-UBA), Ciudad Autónoma de Buenos Aires, Argentina; 2Centro de Investigaciones del Mar y la Atmósfera (CIMA/CONICET-UBA), Ciudad Autónoma de Buenos Aires, Argentina; 3UMI-IFAECI CNRS-CONICET-UBA, Ciudad Autónoma de Buenos Aires, Argentina; 4Pacific Ocean Science and Technology Bldg., Room 401, 1680 East-West Road, University of Hawai’i, Honolulu 96822, Estados Unidos; 5Deutsches Geodätisches Forschungsinstitut und Lehrstuhl für Geodätische Geodynamik, Arcisstr. 21, 80333 München, Germany; 6Departamento de Oceanografía, Servicio de Hidrografía Naval (SHN), Av. Montes de Oca 2124, Ciudad de Buenos Aires, C1270ABV, Argentina
In this work satellite altimetry data and its corrections terms are evaluated in a complex coastal environment. Altimetry data are compared with data obtained from a bottom pressure recorder (BPR) deployed during 22 months. The instrument is moored at 2.5km from the coast in San Matias Gulf, Argentina, at only 1.5km from the nominal intersection of satellite tracks 52 (descending, land-to-ocean transition) and 189 (ascending, ocean-to-land transition) of Jason 2. The 20-Hz S-GDR altimetry product is considerd to evaluate how close to the coast altimetry data are reliable. The BPR also provided the first long-term record of accurate sea level in the region, allowing a precise evaluation of tide models. We first compare how two retracking algorithms affect satellite altimetry data: we considered the classic Brown model (MLE4) and a more recent developed method: ALES (Adaptive Leading Edge Subwaveform Retracker). ALES has the ability to recover more data than MLE4 close to the coast, especially for the track that has a transition from land to ocean. Correlation between the 20-Hz S-GDR altimetry product and the in-situ dataset is 0.99 (95% Confidence Level) when all corrections except DAC and ocean tide are applied to the altimeter data, until a distance of 1.6km to the coast for track 189, and 4km for track 52. The large difference is explained by the fact that the satellite flies from land to ocean along track 52 while it flies from ocean to land along track 189. ALES and MLE4 show similar correlation with in-situ data when applied to satellite altimetry data for distances larger than 17km from the coast. Results also show that both solid earth tide and ionosphere corrections increase the correlation between altimetry and in-situ data near the coast: a correlation value of 0.9 is found at a distance from the coast of 4.1km (track 189) and 1.6km (track 52) when they are applied, instead of 4.6km and 8km respectively. Tide correction also bias the sea level anomaly constructed with satellite data, no matter which tide model is considered. Among the three global and one regional tidal models considered, the model with the lower root sum square of the difference (RSS) is the regional one (TPXO8, 4.8cm). Yet the lowest difference with in-situ tidal constituents is obtained by harmonic analysis of the complete (1992-2014) altimetry data set (RSS 4.1cm) highlihtying the potential of altimetry data to compute tides. Considering data from both ascending and descending tracks we finally show that using ALES and TPXO8 tidal model it is possible to construct a sea level anomaly with a root mean square difference of 13cm as close as 4km from the coast.
Inter-Comparison Between Different Along Track Altimeter Products, Numerical Ocean Models and In Situ Measurements: Development of a Dedicated Software.
1CTOH/LEGOS, OMP, 14 avenue E. Belin, 31400 Toulouse, France; 2Laboratoire d’Aérologie, 14 avenue E. Belin, 31400 Toulouse, France; 3CLS, 11 Rue Hermès, 31520 Ramonville-Saint-Agne, France
Over the last decade, great progress has been made in both coastal altimetry and high resolution ocean modeling. Their use (together or separately) is rapidly evolving. One fundamental issue is then to understand the capabilities of the different coastal altimetry data products and of the different models for coastal applications. In this work, the purpose is the definition of diagnoses which can be computed from coastal alongtrack sea level anomaly products and are adapted to the monitoring of the coastal ocean dynamics. In the framework of the Copernicus program, a new software is under development at the Laboratoire d'Etude en Géophysique et Océanographie Spatiales (France), in collaboration with CLS. The two complementary objectives are:
- the development of new altimetry data validation/intercomparison methods, adapted to the finer scales of the coastal dynamics.
- the analysis of the performance of different high resolution numerical models thanks to alongtrack altimetry measurements.
This tool is based on the inter-comparison between coastal altimetry data sets, model outputs and in-situ measurements. Among these comparisons it is possible to focus on sea level, absolute surface currents or geostrophic surface currents. Different and complementary diagnoses are available. Their combined analysis provides information on the temporal and spatial variability of the coastal ocean dynamics which are captured by altimetry and models, respectively.
In this work, the project will be introduced, some example of diagnoses will be presented and results will be discussed.
SAR Altimetry Processing on Demand Service for CryoSat-2 and Sentinel-3 at ESA G-POD
1ESA-ESRIN; 2He Space/EUMETSAT; 3Progressive Systems/ESRIN; 4Deimos/ESRIN; 5SERCO c/o European Space Agency, Italy
The scope of this poster is to feature the G-POD SARvatore service to users for the exploitation of the CryoSat-2 data, which was designed and developed by the Altimetry Team at ESA-ESRIN EOP-SER (Earth Observation – Exploitation, Research and Development). The G-POD service coined SARvatore (SAR Versatile Altimetric Toolkit for Ocean Research & Exploitation) is a web platform that allows any scientist to process on-line, on-demand and with user-selectable configuration CryoSat-2 SAR/SARIN data, from L1a (FBR) data products up to SAR/SARin Level-2 geophysical data products. The Processor takes advantage of the G-POD (Grid Processing On Demand) distributed computing platform to timely deliver output data products and to interface with ESA-ESRIN FBR data archive (155’000 SAR passes and 41’000 SARin passes). The output data products are generated in standard NetCDF format (using CF Convention), therefore being compatible with the Multi-Mission Radar Altimetry Toolbox and other NetCDF tools. By using the G-POD graphical interface, it is straightforward to select a geographical area of interest within the time-frame related to the Cryosat-2 SAR/SARin FBR data products availability in the service catalogue. The processor prototype is versatile allowing users to customize and to adapt the processing, according to their specific requirements by setting a list of configurable options. After the task submission, users can follow, in real time, the status of the processing. From the web interface, users can choose to generate experimental SAR data products as stack data and RIP (Range Integrated Power) waveforms. The processing service, initially developed to support the development contracts awarded by confronting the deliverables to ESA’s, is now made available to the worldwide SAR Altimetry Community for research &
development experiments, for on-site demonstrations/training in training courses and workshops, for cross-comparison to third party products (e.g. CLS/CNES CPP or ESA SAR COP data products), and for the preparation of the Sentinel-3 Surface Topography Mission, by producing
data and graphics for publications, etc. Initially, the processing was designed and uniquely optimized for open ocean studies. It was based on the SAMOSA model developed for Sentinel-3 Ground Segment using CryoSat data. However, since June 2015, a new retracker (SAMOSA+) is offered within the service as a dedicated retracker for coastal zone, inland water and sea-ice/ice-sheet. In view of the Sentinel-3 launch, a new flavor of the service will be initiated, exclusively dedicated to the processing of Sentinel-3 mission data products. The scope of this new
service will be to maximize the exploitation of the upcoming Sentinel-3 Surface Topography Mission’s data over all surfaces. The service is open, free of charge for worldwide scientific applications and available at https://gpod.eo.esa.int/services/CRYOSAT_SAR/
More info can be read at:
Ships-Squat – A Prominent Effect and How It Can Be Calibrated
Jade University of Applied Sciences Oldenburg, Germany
In addition to satellite altimetry and tide gauges, ships can be used to gather sea surface height (SSH) data. Such data can be used for the calibration and validation of satellite altimeters or as an additional data source for empirical ocean models.
GNSS observations of at least three antennas aboard the ships are used for the precise positioning and attitude calculation. The resulting height has to be corrected for different systematic effects. The most prominent effect is the squat which describes the hydrodynamic sinkage of a ship when sailing through water. It depends on the vessels speed through water, the shape of the ships hull and the under keel clearance. In restricted waterways the effect can reach more than 1 meter. If this effect is calibrated, precise in-situ SSH measurements can be realized.
Within a PhD project at the Jade University in Oldenburg the squat of the research vessel WEGA was measured. The experiment took place near the East Frisian Island Langeoog. The SHIPS method (Shore Independent Precise Squat observation) was used. This method uses kinematic GNSS, is independent of facilities at the shore and takes advantage of an escort boat which represents the undisturbed sea surface. This conference poster will explain the experiment in detail and show the results of the calibration.