Academic journal article Geopolitics, History and International Relations

Insar Applications in Environmental Sciences

Academic journal article Geopolitics, History and International Relations

Insar Applications in Environmental Sciences

Article excerpt

1. Introduction

Since 1978 a new type of remote sensing has been developed - radar remote sensing, but it was not until 1990 when the applications for this type of remote sensing started to be tested. The present paper tries to present the applications for Interferometric Synthetic Aperture Radar (InSAR) by expounding some cogent papers and their results. Even though there is plenty literature for the methodological approach (Adam et al., 2009, Blanco-Sanchez et al., 2008, Poneos and Dana, 2008, Scheuchl et al., 2009, Simonetto and Follin, 2012, Wegmuller et al., 2010, Zhu et al., 2009, Zhu and Bamler, 2010) in this paper we will focus only on the practical approach for this technique.

SAR (Synthetic Aperture Radar) technology involves the existence of a certain type of radar, capable of sending and receiving a long wave signal, based on the move registered by the radar between the antenna mounted on a spacecraft or aircraft, and the object. This type of radar can provide remote images with high resolution. The applications of this technology go beyond the atmosphere into the extraterrestrial environment. An example of extraterrestrial application is the Magellan mission (Campbell, 1995) that studied Venus. The satellite was launched in June 1989 and its mission was to map Venus's surface. The mission lasted for three years and the satellite mapped 98% of the surface with a spatial resolution of the images of about 100 m.

The principle behind this technology is to cast a radar signal towards an object, which is reflected and reaches back to the antenna. Depending on the time and the properties of the reflected beam, the signal is used to generate images. A major advantage of radar images, compared to optic ones, is that they can be acquired during the night and also they have a high spatial resolution of about 1 m.

SAR images started to be acquired in 1978, when the first SAR satellite (SEASAT) was launched but became popular only after the 1990s as technology improved.

After the 1990s many radar satellites were launched: ERS-1 (launched in 1991 by ESA), ERS-2 (launched in 1995), JERS-1 (1992, Japan), RADARSAT (1995, Canada), ALOS PALSAR (2005, Japan). Two of the newest radar satellites are TerraSAR-X (2007) and TanDEM-X (2010), both launched by DLR (German Spatial Agency). TanDEM's mission is to second TerraSAR and to map the entire terrestrial surface to obtain a global digital elevation model with a 1 m resolution.

Closely related with the SAR technology, InSAR (Interferometric Synthetic Aperture Radar) uses at least two SAR images (the product obtained is called interferogram) to track the temporal changes of different objects of interest, to map the vertical movements or the texture changes from certain areas or to obtain a very high resolution DEM.

The InSAR technique is used frequently in earth sciences because it can measure the finest vertical movements, thus it is being used in many domains, especially in monitoring natural hazards. Also, InSAR reveal better results in urban areas because of scatter elements, so this paper focuses mostly on InSAR applications in urban areas.

2. Application of InSAR

The applications for this technology ranges from geology - tectonics and neotectonics, earthquakes, volcanology (Perlock et al., 2009) to geomorphology - elevations and subsidence, sometimes under 1 mm, caused by groundwater over exploitation or by old mines, to glaciology (Bamber et al., 1999, Rott et al., 2007) and to land use - forest monitoring and land use changes (Amarsaikhan et al., 2007, Del Frate et al., 2008), but also in urban applications (Dell'Acqua et al., 2011, Dell'Acqua and Gamba, 2003), building extraction and measuring (Bennett and Blacknell, 2003, Dong et al., 2011), and change detection (Schmitt et al., 2011, Thonfeld and Menz, 2011).

This technique is successfully applied in risk studies, from prevention to mitigation. In these cases InSAR is useful for monitoring the elements at risk, early response and rapid assessment of damages (Brunner et al. …

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