Object based image analysis for remote sensing

TLDR

Remote sensing imagery must be converted into usable information, and as spatial resolution has improved, the field has shifted from per‑pixel analysis to object‑based methods that segment images into multi‑pixel objects—a practice that has grown since the 1970s and accelerated around 2000 with the rise of OBIA/GEOBIA and the availability of high‑resolution data supporting multiple scales. This paper reviews the evolution of object‑based image analysis, aiming to delineate usable objects from imagery while integrating image processing and GIS to exploit spectral and contextual information. The authors conduct a comprehensive literature review of several thousand abstracts, analyzing 820 OBIA‑related articles—including journal papers, book chapters, and conference papers—to trace the development of OBIA/GEOBIA methods. The review shows that early OBIA work was dominated by grey literature, but peer‑reviewed journal articles have surged in the past four to five years, and the pixel paradigm is breaking down as OBIA methods advance toward spatially explicit workflows needed for planning and monitoring.

Abstract

Remote sensing imagery needs to be converted into tangible information which can be utilised in conjunction with other data sets, often within widely used Geographic Information Systems (GIS). As long as pixel sizes remained typically coarser than, or at the best, similar in size to the objects of interest, emphasis was placed on per-pixel analysis, or even sub-pixel analysis for this conversion, but with increasing spatial resolutions alternative paths have been followed, aimed at deriving objects that are made up of several pixels. This paper gives an overview of the development of object based methods, which aim to delineate readily usable objects from imagery while at the same time combining image processing and GIS functionalities in order to utilize spectral and contextual information in an integrative way. The most common approach used for building objects is image segmentation, which dates back to the 1970s. Around the year 2000 GIS and image processing started to grow together rapidly through object based image analysis (OBIA - or GEOBIA for geospatial object based image analysis). In contrast to typical Landsat resolutions, high resolution images support several scales within their images. Through a comprehensive literature review several thousand abstracts have been screened, and more than 820 OBIA-related articles comprising 145 journal papers, 84 book chapters and nearly 600 conference papers, are analysed in detail. It becomes evident that the first years of the OBIA/GEOBIA developments were characterised by the dominance of 'grey' literature, but that the number of peer-reviewed journal articles has increased sharply over the last four to five years. The pixel paradigm is beginning to show cracks and the OBIA methods are making considerable progress towards a spatially explicit information extraction workflow, such as is required for spatial planning as well as for many monitoring programmes.