The main goal of the TerraSAR-X Add-On for Digital Elevation Measurements (TanDEM-X) mission is the generation of a global digital elevation model (DEM) of unprecedented accuracy and coverage. The global TanDEM-X DEM product became available in 2016, surpassed all expectations, and became a reference for a wide range of Earth science, commercial, and geospatial applications. In addition, new information products, such as DEM change maps (DCMs), have been developed and are available to the geoscience and remote sensing community. Beyond the operational products, new science applications have been demonstrated and are summarized in this article, along with experimental data acquisitions. This article also aims to provide an overview of science activities with TanDEM-X data and science data acquisitions planned for the coming years.

Subglacial lakes form beneath ice sheets and ice caps if water is available, and if bedrock and surface topography are able to retain the water. On a regional scale, the lakes modulate the timing and rate of freshwater flow through the subglacial system to the ocean by acting as reservoirs. More than one hundred hydrologically active subglacial lakes, that drain and recharge periodically, have been documented under the Antarctic Ice Sheet, while only approximately 20 active lakes have been identified in Greenland. Active lakes may be identified by local changes in ice topography caused by drainage or recharge of the lake beneath the ice. The small size of the Greenlandic subglacial lakes puts additional demands on mapping capabilities to resolve the evolving surface topography in sufficient detail to record their temporal behavior. Here, we explore the potential for using CryoSat-2 swath-processed data together with TanDEM-X digital elevation models to improve the monitoring capabilities of active subglacial lakes in Greenland. We focus on four subglacial lakes previously described in the literature, and combine the new data with ArcticDEMs to obtain improved measurements of the evolution of these four lakes.We find that with careful tuning of the swath-processor and filtering of the output data, the inclusion of these new data together with the TanDEM-X data provides important information on lake activity, documenting, for example, that the ice surface collapse basin on Flade Isblink Ice Cap was 30 meters deeper than previously recorded.

The paper provides an overview of the German TanDEM-X satellite mission status and its ongoing science activities. The global digital elevation model (DEM) of TanDEM-X became available in 2016 and surpassed all expectations: It has 99.9% coverage, 12-m posting, absolute height accuracy of approximately 1 m and a relative height error (standard deviation) of 0.8 m. This unique data set has been available since then for commercial and scientific applications. In addition, a low-resolution version of the global digital elevation model with 90-m posting has been released for free download for scientific applications [1]. Further a new digital elevation model the TanDEM-X 2020 is expected to be released in mid-2025 and will be available for scientific purposes.

Subglacial lakes form beneath ice sheets and ice caps if water is available and if bedrock and surface topography are able to retain the water. On a regional scale, the lakes modulate the timing and rate of freshwater flow through the subglacial system to the ocean by acting as reservoirs. More than 100 hydrologically active subglacial lakes that drain and recharge periodically have been documented under the Antarctic Ice Sheet, while only approximately 20 active lakes have been identified in Greenland. Active lakes may be identified by local changes in ice topography caused by the drainage or recharge of the lake beneath the ice. The small size of the Greenlandic subglacial lakes puts additional demands on mapping capabilities to resolve the evolving surface topography in sufficient detail to record their temporal behaviour. Here, we explore the potential for using CryoSat-2 swath-processed data, together with TanDEM-X digital elevation models, to improve the monitoring capabilities of active subglacial lakes in Greenland. We focus on four subglacial lakes previously described in the literature and combine the data with ArcticDEMs to obtain improved measurements of the evolution of these four lakes. We find that with careful tuning of the swath processor and filtering of the output data, the inclusion of these data, together with the TanDEM-X data, provides important information on lake activity, documenting, for example, that the ice surface collapse basin on Flade Isblink Ice Cap was 50 % (30 m) deeper than previously recorded. We also present evidence of a new, active subglacial lake in southwestern Greenland, which is located close to an already known lake. Both lakes probably drained within 1 month in the summer of 2012, which suggests either that they are hydrologically connected or that the drainages were independently triggered by extensive surface melt. If the hydrological connection is confirmed, this would to our knowledge be the first indication of hydrologically connected subglacial lakes in Greenland.

Subglacial lakes form beneath ice sheets and ice caps if water is available, and if bedrock and surface topography are able to retain the water. On a regional scale, the lakes modulate the timing and rate of freshwater flow through the subglacial system to the ocean by acting as reservoirs. More than one hundred hydrologically active subglacial lakes, that drain and recharge periodically, have been documented under the Antarctic Ice Sheet, while only approximately 20 active lakes have been identified in Greenland. Active lakes may be identified by local changes in ice topography caused by drainage or recharge of the lake beneath the ice. The small size of the Greenlandic subglacial lakes puts additional demands on mapping capabilities to resolve the evolving surface topography in sufficient detail to record their temporal behavior. Here, we explore the potential for using CryoSat-2 swath-processed data together with TanDEM-X digital elevation models to improve the monitoring capabilities of active subglacial lakes in Greenland. We focus on four subglacial lakes previously described in the literature, and combine the new data with ArcticDEMs to obtain improved measurements of the evolution of these four lakes. We find that with careful tuning of the swath-processor and filtering of the output data, the inclusion of these new data together with the TanDEM-X data provides important information on lake activity, documenting, for example, that the ice surface collapse basin on Flade Isblink Ice Cap was 30 meters deeper than previously recorded.

One-third of Germany's land surface area is covered by forest (around 11.4 million hectares), and thus, it characterizes the landscape. The forest is a habitat for a large number of animal and plant species, a source of raw materials, important for climate protection, and a well-being refuge for people, to name just a few of its many functions. During the annual forest condition surveys, the crown condition of German forests is assessed on the basis of field samples at fixed locations, as the crown condition of forest trees is considered an important indicator of their vitality. Since the start of the surveys in 1984, the mean crown defoliation of all tree species has increased, now averaging about 25% for all tree species. Additionally, it shows a strong rise in the rate of dieback. In 2019, the most significant changes were observed. Due to the drastic changes in recent years, efforts are being made to assess the situation of the forest using different remote sensing methods. There are now a number of freely available products provided to the public, and more will follow as a result of numerous projects in the context of earth-observation (EO)-based monitoring and mapping of the forests in Germany. In 2020, the situation regarding the use of remote sensing for the German forest was already investigated in more detail. However, these results no longer reflect the current situation. The changes of the last 3 years are the content of this publication. For this study, 84 citable research publications were thoroughly analyzed and compared with the situation in 2020. As a major result, we found a shift in the research focus towards disturbance monitoring and a tendency to cover larger areas, including national-scale studies. In addition to the review of the scientific literature, we also reviewed current research projects and related products. In congruence to the recent developments in terms of publications in scientific journals, these projects and products reflect the need for comprehensive, timely, large-area, and complementary EO-based information around forests expressed in multiple political programs. With this review, we provide an update of previous work and link it to current research activities. We conclude that there are still gaps between the information needs of forest managers who usually rely on information from field perspectives and the EO-based information products.

Interferometric synthetic aperture radar (InSAR) data suffer from an elevation bias due to signal penetration into the firn and ice surface, rendering the height information unusable for elevation and mass-change detection. This study estimates the penetration bias in X-band InSAR data to quantify its impact on elevation and mass-change detection and to demonstrate the applicability of TanDEM-X digital elevation models (DEMs) for cryosphere research. To achieve this, a multiple linear regression model is applied to a time series of four TanDEM-X DEMs acquired between 2010 and 2018 over the Sverdrup Glacier basin (SGB), Devon Ice Cap, Canada. The resulting penetration corrected TanDEM-X DEMs agreed to within +/- 14 cm of spatially and temporally coincident precise in situ kinematic dGPS data (+/- 10 cm RMSE). Additionally, multi-year estimations of mass change for the SGB derived from differencing TanDEM-X DEMs over multi-year periods between 2010 and 2018, showed good agreement with mean deviation of 338 +/- 166 mm w.e. with independent measurements of mass change derived from annual in situ surface mass balance over the same time periods. The results show that the penetration bias can vary significantly, leading to random under- and overestimations in the detection of elevation and mass changes.

The HydroSHEDS database provides seamless hydrographic data to support hydro-ecological research and applications on a regional to global scale. A steadily increasing availability and accuracy of remote sensing data promotes the development of a second and refined version of HydroSHEDS, which is based on the TanDEM-X dataset. To derive hydrographic information from the topographic data, the TanDEM-X digital elevation model (DEM) requires editing, which is summarized in the so-called hydrologic pre-conditioning. The processing steps include an infill of voids and outliers in the DEM and the delineation of a global high-resolution coastline. Furthermore, a global water mask is generated to edit rough and noisy appearing open water surfaces in the DEM. An urban correction layer is calculated to reduce distortions in river flow paths due to built-up areas. Within the HydroSHEDS workflow, the preconditioning will be complemented with refined hydrological optimization and correction algorithms. Compared to HydroSHEDS v1, the resulting hydrologically conditioned DEM ensures a more accurate derivation of flow direction and flow accumulation maps.

Space-borne digital elevation models (DEM) are considered as important proxy for canopy surface height and its changes in forests. Interferometric TanDEM-X DEMs were assessed regarding their accuracy in forests of Germany and Estonia. The interferometric synthetic aperture radar (InSAR) data for the new global TanDEM-X DEM 2020 coverage were acquired between 2017 and 2020. Each data acquisition was processed using the delta-phase approach for phase unwrapping and comprise an absolute height calibration. The results of the individual InSAR heights confirmed a substantial bias in forests. This was indicated by a mean error (ME) between – 5.74 and – 6.14 m associated with a root-mean-squared-error (RMSE) between 6.99 m and 7.40 m using airborne light detection and ranging (LiDAR) data as a reference. The bias was attributed to signal penetration, which was attempted to be compensated. The ME and RMSE improved substantially after the compensation to the range of – 0.54 to 0.84 m and 3.55 m to 4.52 m. Higher errors of the penetration depth compensated DEMs compared to the original DEMs were found in non-forested areas. This suggests to use the penetration compensation only in forests. The potential of the DEMs for estimating height changes was further assessed in a case study in Estonia. The canopy height change analysis in Estonia indicated an overall accuracy in terms of RMSE of 4.17 m and ME of – 0.93 m on pixel level comparing TanDEM-X and LiDAR height changes. The accuracy improved substantially at forest stand level to an RMSE of 2.84 m and an ME of – 1.48 m. Selective penetration compensation further improved the height change estimates to an RMSE of 2.14 m and an ME of – 0.83 m. Height loss induced by clearcutting was estimated with an ME of – 0.85 m and an RMSE of 3.3 m. Substantial regrowth resulted in an ME of – 0.46 m and an RMSE of 1.9 m. These results are relevant for exploiting multiple global acquisitions of TanDEM-X, in particular for estimating canopy height and its changes in European forests.

The TanDEM-X mission provides a global digital elevation model (DEM) with high spatial resolution and therefore is able to capture the local geomorphic appearance of the world’s surface. In particular, the high quality and homogeneity enable new possibilities for hydrologic products, where the earth’s relief is a key source of information. As the TanDEM-X DEM is provided in an unedited version some distortions are still present and require pre-processing. In particular, decorrelation effects at open water areas cause a noisy and rough appearance of naturally flat surfaces, which impair hydrological assessments. In this paper an automated global water body classification is presented, utilizing TanDEM-X synthetic aperture radar, optical and terrain data to generate a water mask tailored towards these areas in the DEM. The generated water mask is a vital product for the hydrologic conditioning. The state-of-the-art Gradient Boosted Decision Trees is chosen as the underlying classifier. It is combined with a Bayesian hyperparameter optimization to avoid manual tuning. For the generation of training data, different global water masks are evaluated and appropriate training pixels are identified. First results show the potential of this approach and particularly the advantage in detecting water north of 60deg degrees, when using the lowest Amplitude measured in the feature space.

This paper introduces the new TanDEM-X DEM 2020. The TanDEM-X mission systematically acquired data mainly between September 2017 and mid-2020 to create another global DEM, the so-called “TanDEM-X DEM 2020”, formerly also called TanDEM-X Change DEM. The present paper describes the generation of the TanDEM-X DEM 2020 in terms of the adopted acquisition planning strategy, the new interferometric processing and DEM generation as well as the final DEM product specifications. The main differences from the existing global TanDEM-X DEM (2010-2014) are the new and independent time frame and a new interferometric processing technique with lower phase unwrapping errors, allowing for a mainly single-coverage acquisition strategy except for more difficult terrain. The fewer acquisitions slightly increase the random height errors but still very high accuracy. Examples for height changes on forests and glaciers between TanDEM-X DEM and TanDEM X DEM 2020 round off the paper with large-scale mosaics of Iceland and New Zealand.

We present the generation and validation of an updated version of the TanDEM-X digital elevation model (DEM) of Antarctica: the TanDEM-X PolarDEM 90 m of Antarctica. Improvements compared to the global TanDEM-X DEM version comprise filling gaps with newer bistatic synthetic aperture radar (SAR) acquisitions of the TerraSAR-X and TanDEM-X satellites, interpolation of smaller voids, smoothing of noisy areas, and replacement of frozen or open sea areas with geoid undulations. For the latter, a new semi-automatic editing approach allowed for the delineation of the coastline from DEM and amplitude data. Finally, the DEM was transformed into the cartographic Antarctic Polar Stereographic projection with a homogeneous metric spacing in northing and easting of 90 m. As X-band SAR penetrates the snow and ice pack by several meters, a new concept for absolute height adjustment was set up that relies on areas with stable penetration conditions and on ICESat (Ice, Cloud, and land Elevation Satellite) elevations. After DEM generation and editing, a sophisticated height error characterization of the whole Antarctic continent with ICESat data was carried out, and a validation over blue ice achieved a mean vertical height error of just −0.3 m ± 2.5 m standard deviation. The filled and edited Antarctic TanDEM-X PolarDEM 90 m is outstanding due to its accuracy, homogeneity, and coverage completeness. It is freely available for scientific purposes and provides a high-resolution data set as basis for polar research, such as ice velocity, mass balance estimation, or orthorectification.

Tropical landscapes are relevant in their contribution to global climate regulation as potential carbon sink or source. The sequestered and emitted carbon is commonly approximated with the aboveground biomass (AGB). However, the estimation of AGB is to date mostly focussed on the estimation of one single point in time, where the accuracy is limited in particular on large spatial scales. The interferometric information (i.e. coherence and height) of high-frequency synthetic aperture radar (SAR) systems are considered particularly useful to estimate vegetation height and AGB. It is frequently assumed that the interfometric height of X-band systems like TanDEM-X represent the canopy surface height. Consequently, these interferometric SAR (InSAR) heights can be combined with terrain information to estimate vegetation canopy height and subsequently AGB. No spaceborne system exists to date to estimate the terrain height consistently on a global scale and thus the combination of TanDEM-X InSAR height and terrain information is normally limited to small spatial coverages. The potential to estimate AGB and in particular its change with such an approach is limited. In contrast, TanDEM-X InSAR heights can be directly compared over time. The differences can be assumed as differences in the canopy height assuming that the TanDEM-X InSAR heights represent the canopy surface height at a single point in time. The canopy height differences estimated by calculating the difference between bi- or multi-temporal TanDEM-X InSAR heights can be related to AGB differences. However, it was frequently found that the X-band signal penetrates into the canopy. This results in the fact that the X-band InSAR height is an approximation of the canopy surface height is not true. More importantly, the penetration depth can differ between different acquisitions depending on the acquisition properties and properties on the ground (e.g. moisture), which would result in pseudo-changes in the difference calculation of InSAR height models at different point in times. In our study, we used two TanDEM-X acquisitions from 2012 and 2019 covering a dynamic tropical area in Sumatra, Indonesia. We derived the InSAR heights for each acquisition date individually and calculated their difference. In addition, we assessed the penetration depth of the individual InSAR heights and modelled the penetration to compensate potential pseudo-changes. The absolute accuracy of the individual TanDEM-X heights was assessed with a LiDAR height model used as a reference. The TanDEM-X height differences were further related to ground-based AGB estimations from 2012 and 2019. This resulted in a significant linear relationship between height model and AGB differences, where the penetration compensated height models had a higher coefficient of determination and accuracy compared to the original InSAR heights. However, the accuracy was generally high in both cases with relative root mean square errors below 15%. This suggests that X-band height from TanDEM-X can be used to estimate canopy height differences and subsequently AGB changes on large spatial scale. However, the differences in penetration depth should not be neglected in order to avoid pseudo-changes and to estimate also small changes like degradation or growth.

The TanDEM-X mission is currently acquiring a new dataset to provide a temporally independent DEM, the so-called “TanDEM-X Change DEM”. This set of acquisitions taken between 2017 and 2020 has a clear temporal separation with respect to the data used for the generation of the TanDEM-X global DEM which were acquired between 2010 and 2015. Therefore, this new DEM aims to enable the characterization of terrain changes. Improvements in the acquisition planning process and in the data processing have been necessary to allow the generation of this Change DEM with fewer acquisitions but still very high accuracy. For this, the use of an edited TanDEM-X DEM as a "starting point" for the interferometric processing is mandatory.

The area-wide estimation of aboveground biomass (AGB) and its changes as a proxy for the sequestration and emission of carbon are currently associated with high uncertainties. Here we combined interferometric synthetic aperture radar (InSAR) height models derived from TanDEM-X with repeated ground-based inventories from the years 2012 and 2019 to estimate InSAR height and AGB changes in a structurally diverse and dynamic landscape in Sumatra, Indonesia. The results suggested that the InSAR height models were highly accurate and the relationship between InSAR height and AGB change resulted in a coefficient of determination R-2 of 0.65 and a crossvalidated root mean square error (RMSE) of 2.38 Mg ha(-1) year(-1), equivalent to 13.32% of the actual AGB difference range. The estimated AGB changes with TanDEM-X were further related to the initial canopy height and fire activities in the study area. Initial canopy heights and the occurrences of fires had a significant effect on the AGB change. In general, low canopy heights tend to be associated with increasing AGB over time, whereas high canopy heights tend to be associated with stable or decreasing AGB. As expected, fires had a negative impact on the AGB changes being more pronounced in forest areas compared to oil palm concessions. The results of this study are relevant for the utilization of spaceborne InSAR height models and its potential to estimate canopy height and AGB change on large spatial scales. It was demonstrated that these changes can be related to their sources and ecosystem processes. This AGB change estimation technique can be used to model the impacts of fires on AGB change and carbon emissions, which are important for sustainable forest management.

The global digital elevation model (DEM) produced by the TanDEM-X (TerraSAR-X add-on for digital elevation measurements) mission is an interferometric elevation model with unprecedented quality, accuracy, and coverage. It represents an unedited surface model as artifacts inherent to the interferometric synthetic aperture radar acquisition and processing technique are still present. The most prominent artifacts in the DEM are water bodies appearing with a rough surface due to low coherence. Additionally, outliers, voids, and larger data gaps may be present in this dataset. Therefore, DEM editing is crucial for many applications including hydrology or orthorectification of remote sensing data. Depending on the field of application, different techniques of quality enhancement are required. This article provides a comprehensive description of a semi-automatic framework specially developed for generating an edited version of the TanDEM-X dataset by shaping the high-resolution 12 m DEM with focus on water areas, outlier handling, and void filling. The default configuration parameters of the workflow can thereby be adapted interactively for challenging areas where appropriate. A quality assessment of the resulting edited DEM was done by statistical measures, visual methods, as well as by an artifact evaluation.

On June 21, 2010, the TanDEM-X mission was launched and opened a new era in spaceborne radar remote sensing. The first formation flying radar system was built by extending the TerraSAR-X synthetic aperture radar (SAR) mission by a second, TerraSAR-X-like satellite TanDEM-X. The resulting large single-pass SAR interferometer features flexible baseline selection, enabling the acquisition of highly accurate cross-track interferograms not impacted by temporal decorrelation and atmospheric disturbances. The primary objective of the mission was the generation of a global Digital Elevation Model (DEM) with unprecedented accuracy (12-m horizontal resolution and 2-m relative height accuracy). The main mission phase for DEM data acquisition has been finished in 2014; the processing of the global TanDEM-X DEM was concluded in September 2016. The final DEM product is well within specifications and features an extremely low percentage of void areas. It is of fundamental importance for a wide range of commercial and scientific applications. But the scientific exploitation of TanDEM-X is not limited to the DEM. TanDEM-X has unique capabilities, including along-track interferometry, and new bistatic and multistatic SAR techniques, that support numerous secondary mission objectives. Indeed, some of these experiments were directly performed during the DEM acquisition phase, when suitable satellite formation geometries were available. Moreover, regular acquisitions over selected super test sites enabled multitemporal analyses. A dedicated science phase after the DEM acquisitions included up to 4 km cross-track baselines, operation in the so-called Dual-Receive Antenna mode, as well as a period in pursuit monostatic flight formation. Comparisons of the TanDEM-X DEM with that of SRTM, or among multitemporal TanDEM-X data, revealed dramatic, ongoing, changes in Earth's topography, especially over ice and forests. In the last 3.5 years the mission has further acquired data for a global change layer showing the height changes relative to the first global DEM dataset. The so-called “Change DEM” is planned for release in 2021. Despite being well beyond their design lifetime, both satellites are still fully functional and have enough consumables for several additional years. Therefore, bistatic operations continue with a focus on changes in the cryosphere, biosphere, and densely populated urban areas.

Multi-temporal analysis of canopy surface heights has high potential for a forest monitoring system. TanDEM-X interferometric synthetic aperture radar (InSAR) heights provide a global data source for a multi-temporal height analysis as two global coverages from the global digital elevation model (DEM) phase 2010-2014 and the Change DEM phase 2017-2020 exist. However, the potential of estimating small scale and subtle changes with TanDEM-X heights is to date underexplored. The detection of subtle changes was assessed in this study. Penetration depth estimations were applied as a first step in a framework to avoid pseudo-changes based on errors and different acquisition properties. The results suggest that subtle changes are detectable, but an improved error assessment is necessary in order to provide a detection with high accuracy.

The Greenland Ice Sheet (GIS) was the largest contributor to global sea level rise in the 2005 to 2016 period (Meredith et al. in press). Therefore, it is one of the biggest players influencing our climate and monitoring and understanding of its mechanisms and development are of highest relevance. Means to observe and measure such large areas are remote sensing. The Tandem-X mission of DLR and Airbus consists of two satellites (TerraSAR-X and TanDEM-X) that are flying in single pass formation, mapping the Earth in interferometric SAR X-band with a resolution of 12m (Zink et al. 2014). The mission has been flying in this constellation since 2010. Due to the satellite constellation and the SAR system, digital elevation models (DEMs) can be created in high resolution, unaffected by the availability of daylight and the presence of clouds. All data acquired between 2010 to 2014 (Rizzoli et al. 2017) were compled to a global elevation model. Besides this global product, several time slices were created for the GIS (Wohlfart et al. 2018). In this project, we created a DSM mosaic from winter 2015/16 acquisitions, more precisely using more than 2000 DEM scenes (Fritz at al. 2011) from end of October 2015 to beginning of February 2016. One issue of a SAR system is the penetration of the signal into snow. Additionally, water surfaces appear dark in the images due to low backscatter towards the sensor. Therefore, we used winter scenes to minimize the height error. We created an almost seamless DSM out of these scenes for 2015/16. Second, we used SAR features to delineate different snow zones. For this purpose, we used the amplitude, the height error map, and additionally ICESat and ICE Bridge data. References Fritz, T.; Rossi, C.; Yague-Martinez, N.; Rodriguez Gonzalez, F.; Lachaise, M.; Breit H. Interferometric processing of TanDEM-X data, IGARSS 2011, Vancouver, July 2011 Meredith, M.; Sommerkorn M.; Cassotta S.; Derksen C.; Ekaykin A.; Hollowed A.; Kofinas G.; Mackintosh A.; Melbourne-Thomas J.; Muelbert M.M.C.; Ottersen G.; Pritchard H.; and Schuur E.A.G.; 2019: Polar Regions. In: IPCC Special Report on the Ocean and Cryosphere in a Changing Climate [H.-O. Pörtner, D.C. Roberts, V. Masson-Delmotte, P. Zhai, M. Tignor, E. Poloczanska, K. Mintenbeck, A. Alegría, M. Nicolai, A. Okem, J. Petzold, B. Rama, N.M. Weyer (eds.)]. In press. Rizzoli, P.; Martone, M.; Gonzalez, C.; Wecklich, C.; Tridon, D.B.; Bräutigam, B.; Bachmann, M.; Schulze, D.; Fritz, T.; Huber, M.; et al. Generation and performance assessment of the global TanDEM-X digital elevation model. ISPRS J. Photogramm. Remote Sens. 2017, 132, 119–139. Wohlfart, C.; Wessel, B.; Huber, M.; Leichtle, T.; Abdullahi, S.; Kerkhoff, S.; Roth, A. TanDEM-X DEM derived elevation changes of the Greenland Ice Sheet. In Proceedings of the IEEE International Geoscience and Remote Sensing Symposium (IGARSS), Valencia, Spain, 22–27 July 2018. Zink, M.; Bachmann, M.; Bräutigam, B.; Fritz, T.; Hajnsek, I.; Krieger, G.; Moreira, A.; Wessel, B. TanDEM-X: The New Global DEM Takes Shape. IEEE GRSM 2014, 2, 8–23.

In this study we present the digital elevation model (DEM) for Antarctica produced by the TanDEM-X (TerraSAR add-on for digital elevation measurement) mission. The TanDEM-X Polar DEM 90 is a reduced version of the global TanDEM-X DEM with special adaptations. Holes were filled with additional acquisitions and water areas were flattened to avoid noisy height values. The resulting DEM from SAR interferometry is outstanding due to its resolution, accuracy, consistency and coverage completeness. The TanDEM-X Polar DEM-90 is freely available for scientific use and provides a high resolution dataset as basis for research, e.g. on climate change, in Antarctica. This study focuses on the application of this DEM for hydrology on the basis of several hydrological DEM based features: flow direction, flow accumulation, slope, streams and catchment boundaries. These features were developed for liquid water flow. Their application and usefulness for icy regions will be investigated in this study. The joint interpretation of hydrologic features with geophysical measurements, e.g. ice velocity and further hydrological elements like supra- and subglacial lakes may enable a more in detail understanding of the ongoing processes on the ice.