The New TanDEM-X Change DEM: Specification and Interferometric Processing

Since 2017, the TanDEM-X mission aims to acquire data globally to generate another (updated) DEM. This new set of acquisitions, which will be complete in 2020, has a clear temporal separation from those used for the TanDEM-X global DEM. It will therefore allow the creation of a temporally independent DEM, the so-called “TanDEM-X Change DEM” enabling the characterization of terrain changes. Since only one global coverage is being acquired, improvements in e.g. the interferometric data processing are necessary. In particular, an edited version of the existing global TanDEM-X DEM is now the "starting point" for the interferometric processing as detailed in this paper

Change Detection within the Processing of the TanDEM-X Change DEM

Over the last years the TanDEM-X mission acquired data for a second global digital elevation model (DEM) the TanDEM-X Change DEM. This new DEM is temporally independent of the former global TanDEM-X DEM and therefore yields the possibility of change detection. In order to decrease the phase noise level the interferometric processing for the Change DEM has been upgraded. This also allows a more accurate change detection. Currently, the processing of the global data is performed operationally. It includes the detection of terrain changes and first examples of detected terrain changes can be presented

Assessment of TanDEM-X DEM 2020 Data in Temperate and Boreal Forests and Their Application to Canopy Height Change

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

TanDEM-X DEM 2020: What is new?

In the last years, the TanDEM-X mission systematically acquired data to create another global DEM, the so-called 'TanDEM-X DEM 2020', mainly between September 2017 and mid-2020. This contribution describes the status of the generation of this second global TanDEM-X DEM with special focus on procedural and algorithmic modifications compared to the first global TanDEM-X DEM

The TanDEM-X 30m DEM Change Maps: applications and further developments

The TanDEM-X mission has been acquiring continuously bistatic data from which DEM are derived since 2010. The outstanding quality of these DEMs enables the observation of changes that occur on the whole Earth’s landmass. This paper presents the new product of the TanDEM-X mission, the TanDEM-X 30m DEM Change Maps, which is availa-ble for free for scientific and non-commercial use since November 2023. Various applications which are primordial for climate change monitoring are introduced and show how the DEM Change Maps can be a very useful input to derive information about e.g. glacier melting, mining monitoring or deforestation globally. Finally, the next developments to-wards building DEM Change Maps time series are explained

TanDEM-X DEM Change Maps Stacks: Towards TanDEM-X 4D

The TanDEM-X mission acquires data used for the generation of Digital Elevation Models (DEMs) since 2010. From this data two global DEMs are already generated or in generation. The DEM acquisitions used for new TanDEM-X DEM 2020 are also used to generate TanDEM-X DEM Change Maps. Furthermore, the DEM Change Maps can be combined with the additional TanDEM-X DEM datasets and used for the generation of TanDEM-X DEM Change Map Stacks. This paper presents these new products on the basis of an exam ple of an open-pit mining area in Australia. Additionally, the potentials and challenges of the DEM Change Map stacks are presented

An Adaptive Filtering Approach for the New TanDEM-X Change DEM

The TanDEM-X Change DEM will be a new DEM consisting of the data globally acquired by the TanDEM-X mission from 2017 until 2020. This new DEM aims to characterize terrain changes which occurred between the acquisition of the TanDEM-X global DEM, acquired between 2010 and 2015, and the new temporally independent and up-to-date data set. The new data will mostly contain only one global coverage. Therefore, necessary improvements in the acquisition planning process as well as in the interferometric processing were made. Specifically, a new adaptive filtering approach is presented in this paper as well as its influence on the interferometric phase and the DEM for test sites over Germany and Chile

The TanDEM-X Change DEM: Status of the CRawDEMs production

In 2017, the TanDEM-X Mission decided to generate a second - more recent - global DEM. The acquisitions took place from 2017 till mid 2020 and represent a new global coverage of the whole Earth's landmass. This global dataset is well separated in time from the data used for the first global TanDEM-X DEM. Recent terrain height information can be delivered globally again with similar accuracy and consequently, terrain changes can be monitored. Currently, this data is being processed by the Integrated TanDEM-X Processor (ITP) into pre-calibrated single scenes. A reference DEM is a pre-requisite to enable a correct interferometric processing