Bare-earth extraction and DTM generation from photogrammetric point clouds including the use of an existing lower-resolution DTM

ABSTRACT

A method of extracting bare-earth points from photogrammetric point clouds by partially using an existing lower resolution digital terrain model (DTM) is presented. The bare-earth points are extracted based on a threshold defined by local slope. The local slope is estimated from the lower resolution DTM. A gridded DTM is then interpolated from the extracted bare-earth points. Five different interpolation algorithms are implemented and evaluated to identify the most suitable interpolation method for such non-uniformly scattered data. The algorithm is tested on four test sites with varying topographic and ground cover characteristics. The results are evaluated against a reference DTM created using aerial laser scanning. The deviations of the extracted bare-earth points, and the interpolated DTM, from the reference DTM increases with increasing forest canopy density and terrain roughness. The DTM created by the method is significantly closer to the reference DTM than the lower resolution national DTM. The ANUDEM (Australian National University Digital Elevation Modelling) interpolation method is found to be the best performing interpolation method in terms of reducing the deviations and in terms of modelling the terrain realistically with minimum artefacts, although the differences among the interpolation methods are not considerably large.

Acknowledgments

The author is very grateful to the Norwegian Institute of Bioeconomy Research (NIBIO) for funding and hosting the Project (Number 450300). All the Norwegian institutes that are directly or indirectly involved in the creation of some of the data used in this study, such as the national DTM and the ALS data, are acknowledged. The author is also very grateful to his colleagues Knut Bjørkelo, Johannes Breidenbach, Johannes Rahlf, Jostein Frydenlund, Hildegunn Norheim, Rasmus Astrup, Ingvild Nystuen, and Rengifo Ortega (from the Norwegian Water and Energy Directorate) for constructive discussions. The author thanks the anonymous reviewers and the Editor of the journal for their useful comments.

Disclosure statement

No potential conflict of interest was reported by the author.

Additional information

Funding

This work was supported by the Norwegian Institute of Bioeconomy Research (NIBIO) under the project number of [450300].