Quality of TanDEM-X DEM. Digital Elevation Models and Factors Affecting Their Accuracy

Ing. Kateřina Gdulová

Disertační práce

Abstract:

Over the past two decades, significant advances in computing and spatial data collection using remote sensing have greatly expanded the availability of digital elevation models (DEMs). A notable recent addition to global DEMs is the radar-based TanDEM-X DEM, available since 2016, which offers an unprecedented spatial resolution of 0.4 arcsec (~12 m at the equator). In December 2019, this non-edited product was followed by the release of a publicly available, improved, edited, and downscaled version (1 arcsec, ~30 m at the equator) known as the Copernicus DEM. DEMs are essential for a wide range of environmental applications, many of which are related to mountains, including studies on natural hazards, forestry, or glacier mass changes. However, synthetic aperture radar interferometry used for the acquisition of TanDEM-X DEM is especially challenging over steep and irregular mountain terrains due to shadowing and foreshortening effects. Therefore, it is important to investigate the limitations and potential biases of newly available datasets in such environments. This dissertation aimed to evaluate the performance of the TanDEM-X DEM in mountainous regions and to assess how its absolute vertical accuracy varies in response to environmental attributes such as terrain slope, aspect, and vegetation cover. Moreover, we concentrated on the rarely used data acquisition characteristics (coverage map, consistency mask, and height error map) and their usability for estimating vertical accuracy and identifying problematic sites. Additionally, we examined the effectiveness of editing procedures used for the Copernicus DEM construction. Finally, we explored the potential of using the TanDEM-X DEM in combination with other global DEMs for multitemporal studies, illustrated by tracking vegetation changes over time. This dissertation provides a broad overview of the TanDEM-X DEM vertical accuracy, with a focus on complex mountainous terrains. Our findings confirm the high accuracy of the TanDEM-X DEM and its derivatives, while also highlighting their limitations and potential bottlenecks. We emphasize the importance of considering environmental characteristics, data acquisition parameters, and post-processing techniques when using global DEMs for different environmental applications. Unfortunately, a broader use of TanDEM-X DEM is limited by the fact that only the coarser-resolution versions are freely available. The 12 m version, which represents a major achievement of the mission, continues to be of limited availability, only provided based on scientific proposals.

Keywords

global DEM, DSM, DTM, vertical accuracy, validation, mountain

Jazyk práce: angličtina

Datum vytvoření / odevzdání či podání práce: 16. 9. 2024

Obhajoba závěrečné práce

• Vedoucí: doc. Ing. Vítězslav Moudrý, Ph.D.
• Oponent: Vít Penížek, Ph.D.

Česká zemědělská univerzita v Praze

Fakulta životního prostředí

Doktorský studijní program:
Aplikovaná a krajinná ekologie