EXPLOITING SHADOW EVIDENCE AND ITERATIVE GRAPH-CUTS FOR EFFICIENT DETECTION OF BUILDINGS IN COMPLEX ENVIRONMENTS

This paper presents an automated approach for efficient detection of building regions in complex environments. We investigate the shadow evidence to focus on building regions, and the shadow areas are detected by recently developed false colour shadow detector. The directional spatial relationship between buildings and their shadows in image space is modelled with the prior knowledge of illumination direction. To do that, an approach based on fuzzy landscapes is presented. Once all landscapes are collected, a pruning process is applied to eliminate the landscapes that may occur due to non-building objects. Thereafter, we benefit from a graph-theoretic approach to accurately detect building regions. We consider the building detection task as a binary partitioning problem where a building region has to be accurately separated from its background. To solve the two-class partitioning, an iterative binary graph-cut optimization is performed. In this paper, we redesign the input requirements of the iterative partitioning from the previously detected landscape regions, so that the approach gains an efficient fully automated behaviour for the detection of buildings. Experiments performed on 10 test images selected from QuickBird (0.6 m) and Geoeye-1 (0.5 m) high resolution datasets showed that the presented approach accurately localizes and detects buildings with arbitrary shapes and sizes in complex environments. The tests also reveal that even under challenging environmental and illumination conditions (e.g. low solar elevation angles, snow cover) reasonable building detection performances could be achieved by the proposed approach

High resolution and high cadence time series of land surface categories, land use land cover, and land use land cover changes

A prototype of monthly, 10 m resolution land surface categories, land use land cover (LULC) cover, and LULC change maps derived from Sentinel-2 data over three areas within Belgium, Portugal, and Sicily for the period 2018-2020. The LULC and LULC change maps were independently validated by IIASA. All products were generated within the framework of the RapidAI4EO project, funded from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101004356. The data description can be found below. The validation report of the LULC and LULC change maps can be found in validation_LULC.pdf and validation_change.pdf, respectively, and the validation dataset can be found in Lesiv et al. (2023). Data description Increasing the cadence of the land cover updates from the typical (multi-)annual to monthly cadence poses several challenges. First, several land cover types are difficult to discriminate without any knowledge of temporal dynamics. For instance, croplands are characterized by a dynamic of vegetation growth and a harvest period (i.e. cycles of bare soil, sparsely vegetated and vegetated periods). This contrasts with grasslands that often lack the harvest period resulting in a bare soil cover. Without this temporal information, it is difficult to distinguish a vegetated cropland field from grassland. Second, phenological changes may introduce a large intra-class variability and thus also confusion between classes. For example, the shedding of leaves during autumn or wilting of herbaceous vegetation in dry summer periods introduces spectral variability within land cover classes. To overcome these challenges, we developed a workflow with two main phases. The first phase aims to map land surface categories (LSC) at a monthly resolution. The next phase uses the resulting monthly LSC probability time series to classify land cover