Potential of Pléiades and WorldView-3 Tri-Stereo DSMs to Represent Heights of Small Isolated Objects

Abstract

High-resolution stereo and multi-view imagery are used for digital surface model (DSM) derivation over large areas for numerous applications in topography, cartography, geomorphology, and 3D surface modelling. Dense image matching is a key component in 3D reconstruction and mapping, although the 3D reconstruction process encounters difficulties for water surfaces, areas with no texture or with a repetitive pattern appearance in the images, and for very small objects. This study investigates the capabilities and limitations of space-borne very high resolution imagery, specifically Pléiades (0.70 m) and WorldView-3 (0.31 m) imagery, with respect to the automatic point cloud reconstruction of small isolated objects. For this purpose, single buildings, vehicles, and trees were analyzed. The main focus is to quantify their detectability in the photogrammetrically-derived DSMs by estimating their heights as a function of object type and size. The estimated height was investigated with respect to the following parameters: building length and width, vehicle length and width, and tree crown diameter. Manually measured object heights from the oriented images were used as a reference. We demonstrate that the DSM-based estimated height of a single object strongly depends on its size, and we quantify this effect. Starting from very small objects, which are not elevated against their surroundings, and ending with large objects, we obtained a gradual increase of the relative heights. For small vehicles, buildings, and trees (lengths <7 pixels, crown diameters <4 pixels), the Pléiades-derived DSM showed less than 20% or none of the actual object’s height. For large vehicles, buildings, and trees (lengths >14 pixels, crown diameters >7 pixels), the estimated heights were higher than 60% of the real values. In the case of the WorldView-3 derived DSM, the estimated height of small vehicles, buildings, and trees (lengths <16 pixels, crown diameters <8 pixels) was less than 50% of their actual height, whereas larger objects (lengths >33 pixels, crown diameters >16 pixels) were reconstructed at more than 90% in height.

Geometric Accuracy Assessment of Deimos-2 Panchromatic Stereo Pairs: Sensor Orientation and Digital Surface Model Production

“…Most of these VHR sensors have already been studied over the last 20 years [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ], with orthoimages and digital surface models (DSM) being the flagship georeferenced products derived from them. Both products need a sensor orientation phase (also known as the triangulation process) as a previous and crucial step.…”

“…With regard to DSM generation from VHR satellite stereo pairs, the semiglobal matching (SGM) algorithm [ 17 ] is often the most popular in routine production workflows where robustness and efficiency are required. This digital matching algorithm is considered very robust and is able to reduce large outliers in low or non-textured areas while preserving edges and sharp object boundaries [ 18 ], being the choice in most of the most recent published works [ 11 , 18 , 19 , 20 ]. In Aguilar et al [ 19 ] and Nemmaoui et al [ 20 ], the image matching method based on hierarchical SGM yielded better results than the traditional image matching method based on area-based matching and the cross-correlation threshold.…”

“…There are several works about DSM generation from VHR satellite imagery over different types of land covers, including urban areas [ 18 , 25 ], agricultural greenhouse areas [ 20 ], active tectonics [ 26 ], forest [ 24 ], glaciers [ 27 ] and even small isolated objects [ 11 ]. DSM quality assessment is usually carried out by studying its completeness and vertical accuracy [ 18 , 19 , 20 , 21 , 25 , 28 ], defining completeness as the percentage of correctly matched points over the area of interest [ 28 ].…”

“…Most of these VHR sensors have already been studied over the last 20 years [1][2][3][4][5][6][7][8][9][10][11], with orthoimages and digital surface models (DSM) being the flagship georeferenced products derived from them.…”

Innovations in Photogrammetry and Remote Sensing: Modern Sensors, New Processing Strategies and Frontiers in Applications

“…Qiao et al [ 2 ] presented a novel method for detecting changes after a natural disaster using an optical flow-based method and adaptive thresholding segmentation able to detect pixel-based motion tracking at fast speed from video sequences composed of successive passages of high-resolution satellites. Papers based on satellite data include the work by Loghin et al [ 3 ]. These authors discuss the use of high-resolution stereo and multi-view imagery for digital surface model (DSM) derivation over large areas for numerous applications in topography, cartography, geomorphology, and 3D surface modelling.…”