Abstract
The generation of digital surface models (DSMs) from multi-view high-resolution (VHR) satellite imagery has recently received a great attention due to the increasing availability of such space-based datasets. Existing production-level pipelines primarily adopt a multi-view stereo (MVS) paradigm, which exploit the statistical depth fusion of multiple DSMs generated from individual stereo pairs. To make this process scalable, these depth fusion methods often adopt simple approaches such as the median filter or its variants, which are efficient in computation but lack the flexibility to adapt to heterogenous information of individual pixels. These simple fusion approaches generally discard ancillary information produced by MVS algorithms (such as measurement confidence/uncertainty) that is otherwise extremely useful to enable adaptive fusion. To make use of such information, this paper proposes an efficient and scalable approach that incorporates the matching uncertainty to adaptively guide the fusion process. This seemingly straightforward idea has a higher-level advantage: first, the uncertainty information is obtained from global/semiglobal matching methods, which inherently populate global information of the scene, making the fusion process nonlocal. Secondly, these globally determined uncertainties are operated locally to achieve efficiency for processing large-sized images, making the method extremely practical to implement. The proposed method can exploit results from stereo pairs with small intersection angles to recover details for areas where dense buildings and narrow streets exist, but also to benefit from highly accurate 3D points generated in flat regions under large intersection angles. The proposed method was applied to DSMs generated from Worldview, GeoEye, and Pleiades stereo pairs covering a large area (400 km2). Experiments showed that we achieved an RMSE (root-mean-squared error) improvement of approximately 0.1–0.2 m over a typical Median Filter approach for fusion (equivalent to 5–10% of relative accuracy improvement).
Highlights
The number of very high-resolution (VHR) optical satellite sensors has increased drastically over the last two decades
We considered weighting the contributions of the individual digital surface models (DSMs) (Section 4.3), showing that the results of the fusion could be further enhanced by appropriately weighting DSMs of better quality in the fusion procedure
This paper proposed a novel depth fusion algorithm for very-high-resolution (VHR)
Summary
The number of very high-resolution (VHR) optical satellite sensors has increased drastically over the last two decades. A MVS solution directly performs the fusion on the DSM generated by individual stereo pairs, which are previously relatively orientated (instead of a full bundle adjustment for all the images). This has three advantages over the MIM solutions: first, the relative orientation only requires tie points between a selected pair of images instead of all images, which is much less demanding. Gaussian kernel to multiple ones [2], or to adopt postprocessing techniques that utilize the associated orthophotos [12] to enforce image segmentation constraints These fusion methods often assume that the contributions of each measurement are identical, and rarely consider the use of a priori knowledge inherited from the photogrammetric stereo processing that is already existing in the MVS pipeline.
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