Remote sensing in physical geography: a twenty-fi rst-century perspective

Timely, high-quality data from remote sensing can benefi t the study of physical geography in many ways (Wolman, 2004). Rapid developments in remote sensing, particularly from satellite platforms, have generated much, often well-placed, enthusiasm about its potential as a powerful research tool (Skole, 2004). Indeed, remote sensing is viewed by many as having come of age (Tatem et al., 2008) and can be deemed a mature discipline with its physical principles well understood and its range of applications a showcase of its versatility (Warner et al., 2009). Historically, physical geography has benefited greatly from the emergence of new technologies, like remote sensing, and is likely to continue to reap benefi ts from further technological advances in the foreseeable future (Rhoads, 2004). The beginning of the twenty-fi rst century promised to be a period of technological innovation, with remote sensing identifi ed as one of 21 technologies well placed to meet contemporary issues and challenges facing society (AllBusiness, 2001). Given that many of these challenges involve the interaction between society and the physical environment (Demeritt, 2009), and that there is an increasing need for all areas of science, including physical geography, to iterate their value to society (Rediscovering Geography Committee, NRC, 1997), the close of the fi rst decade of the twenty-fi rst century is a suitable point at which to take stock of current trends and developments in remote sensing within physical geography and interrelated fi elds. Remote sensing is useful for the physical geographer not only as a tool for data collection, with superiority over other techniques by virtue of its spatial and temporal coverage, but also because of the logic implicit in the reasoning process employed to analyse the data (Estes et al., 1980). In addition to the experimental, hypothetical and case-study style of reasoning that tends to characterize the use of remote sensing within physical geography, there are increasingly operational modes of usage (eg, within meteorology and climatology, hazard management). Since the turn of the twenty-fi rst century more than 100 satellite sensors have been launched (www.itc.nl/research/products/sensordb/ searchsat.aspx) and numerous airborne and terrestrial sensors manufactured. Many of these sensors are the result of emerging technologies (eg, Krabach, 2000), with the processing and interpretation of the data acquired benefiting from advanced pro-