Earth observation using radar data: an overview of applications and challenges

Abstract

International audienceAbstract The first pictures of the earth were taken from a balloon in the mid-19th century and thus started ‘earth observation’. Aerial missions in the 20th century enabled the build-up of outstanding photographic libraries and then with Landsat-1, the first civilian satellite launched in 1972, digital images of the earth became an operational reality. The main roles of earth observation have become scientific, economic and strategic, and the role of synthetic aperture radar (SAR) is significant in this overall framework. Radar image exploitation has matured and several operational programs regularly use SAR data for input and numerous applications are being further developed. The technological development of interferometry and polarimetry has helped further develop these radar based applications. This paper highlights this role through a description of actual applications and projects, and concludes with a discussion of some challenges for which SAR systems may provide significant assistance

Hazards, Risk, and Vulnerability

“…The utilization of microwave data on inundation mapping has also encountered a few problems in conjunction with some success (Palmann et al 2008 ) . One problem is associated with radar wavelengths and terrain characteristics.…”

“…The innovation of microwave RS, particularly radar RS, resolves the problem associated with optical sensors, although microwave data may produce different types of errors (Palmann et al 2008 ;Dewan et al 2006 ;Taft et al 2003 ;Töyora et al 2002 ) . However, radar RS is a viable alternative data source to traditional optical sensing (Foody 1988 ) , particularly for monsoon countries (Imhoff et al 1987 ) .…”

“…As early as 1967, data from the radar systems were important for detecting and mapping water bodies because of their sensitivity to moisture conditions (Waite et al 1981 ) . In addition to its all-weather capability, SAR images have become the most familiar approach to studying fl ooding and associated problems around the world (Palmann et al 2008 ) . Another key advantage of using SAR data is that land and water can easily be distinguished (Töyora et al 2002 ) .…”

Applications of satellite ‘hyper-sensing’ in Chinese agriculture: Challenges and opportunities

“…The article suggests that the multifrequency, multi-polarisation capability provided by SIR-C/X-SAR was unsurpassed by any spaceborne system, making the data set valuable for algorithm development and assessment of optimal imaging parameters (Evans, 2006). A similar review on the applications and challenges of using radar data for earth observation was also provided by Palmann et al (2008). Table 4 summarises characteristics of suitable SAR satellite systems for agricultural applications.…”

Application of differential synthetic aperture radar interferometry (DINSAR) to the monitoring of ground and structure movements

“…A common statement to all the applications is that the sensitivity of the sensors to measure ground displacements depends on the sensor's wavelength. Moreover, the frequency band determines the penetrability of the SAR sensors (Palmann et al, 2008). In this way, theoretically, X-band sensors with a wavelength of 3.0 cm, almost half of the wavelength of C-band (5.4 cm) and 8 times lower than L-band (24.0 cm), presents a higher resolution.…”