In this book are reported nine works related to land subsidence monitoring using remote sensing techniques. Land subsidence is a common phenomenon in many regions of the world, where it causes degradation of local ecosystems and disruption of economic activities. Its effects are more evident in densely populated areas in particular in low-lying territories such as river deltas and coastal areas where the combination of land subsidence and sea level rise increases the flooding risk. For this reason, the monitoring of ground deformations is a crucial step to obtain important information for the development of risk mitigation strategies. In the presented papers, the characteristics of land subsidence occurring in different study areas are described, and recent developments in the used methodologies for the monitoring of the ground displacements are discussed and validated also by means of ground-based data. Moreover, advantages and disadvantages of the adopted techniques are highlighted. The outcomes of these research works can provide national and local authorities with useful information for the implementation of integrated monitoring systems in the areas most affected by land subsidence.

This book is the product of five and a half years of research dedicated to the und- standing of radar interferometry, a relatively new space-geodetic technique for m- suring the earth’s topography and its deformation. The main reason for undertaking this work, early 1995, was the fact that this technique proved to be extremely useful for wide-scale, fine-resolution deformation measurements. Especially the interf- ometric products from the ERS-1 satellite provided beautiful first results—several interferometric images appeared as highlights on the cover of journals such as Nature and Science. Accuracies of a few millimeters in the radar line of sight were claimed in semi-continuous image data acquired globally, irrespective of cloud cover or solar illumination. Unfortunately, because of the relative lack of supportive observations at these resolutions and accuracies, validation of the precision and reliability of the results remained an issue of concern. From a geodetic point of view, several survey techniques are commonly available to measure a specific geophysical phenomenon. To make an optimal choice between these techniques it is important to have a uniform and quantitative approach for describing the errors and how these errors propagate to the estimated parameters. In this context, the research described in this book was initiated. It describes issues involved with different types of errors, induced by the sensor, the data processing, satellite positioning accuracy, atmospheric propagation, and scattering character- tics. Nevertheless, as the first item in the subtitle “Data Interpretation and Error Analysis” suggests, data interpretation is not always straightforward.