An innovative technique for the remote assessment of ground displacements, based on radar interferometry and implemented using ground-based instrumentation (GB-InSAR), has been tested in recent years on a number of selected case sites. The system, known as LISA, developed by the Joint Research Centre (JRC) of the European Commission, is a ground-based radar interferometer specifically designed for field use. It is composed of two radar antennas mounted on a linear rail which horizontally slides to form a synthetic aperture. Coherent SAR processing converts the raw data into an image containing, for each pixel, information on the wave phase, which depends on the target-sensor distance. Consecutive couples of SAR images can be cross-correlated to form interferograms representing phase variations which can be directly related to ground displacement along the sight-line of the radar system, since they are acquired from exactly the same position. Several applications of the system have been conducted on a number of mass movements located in Italy, in order to validate the technique for the monitoring of landslides. GB-InSAR has proved its potential for the measurement of the superficial ground displacements of different landslide types, in terms of failure mechanism, materials involved, kinematics, water content and deformation rates. In particular conditions, such as fast-moving phenomena and inaccessible areas, the technique can be employed directly as a monitoring tool, providing multi-temporal displacement maps of the observed area. Additionally, some applications of the GB-InSAR have provided a fundamental support to decision makers during landslide emergencies, allowing the civil protection authorities to assess the risk and to manage an effective emergency response.

This paper concerns the use of Ground-Based Synthetic Aperture Radar (GB-SAR) interferometer for the measurement of terrain movements and structural deformations in man-made structures. This instrument can measure displacements with a precision up to a fraction of millimetre. The spatial extension of the monitored area can be of a few squared kilometres. With respect to other traditional geotechnical instruments, the presented GB-SAR interferometer can remotely monitor the target scene, providing deformation maps and not only point-like measurements.

Thermal Infrared (TIR) techniques have some interesting capabilities that may assist in the detection of shallowly buried objects, in particular to help in the identification of landmine contaminated areas. The working principle of the sensor is the measurement of the thermal contrast on the soil surface, caused by the disturbance of the thermal flow due to the presence of the buried object with respect to the surroundings.This paper presents some preliminary results for the detection of buried antipersonnel landmines (APLs) with a thermal infrared imaging system. We describe an algorithm for the detection of landmine candidates by exploiting features in the image associated with the observed thermal contrast. Different threshold levels are applied to select groups of pixels that correspond to hot formations in the image, and are the ones that could indicate a target position.A logical AND combination that is then applied to the produced binary images, and can deliver an acceptable performance for landmine detection. However the method cannot distinguish landmine candidates from background variations sharing similar spatial patterns.Since the performance of the method depends strongly on the environmental conditions, a time series measurement is potentially a more promising approach to the whole problem of thermal IR measurement of buried objects. The time series of the IR data set presented in this paper was collected from the test lanes of JRC in Ispra, Italy, in the framework of the Multi-sensor Mine-signature (MsMs) measurement project.

Synthetic aperture radar (SAR) data are collected by a ground‐based radar system forming the synthetic aperture by the sliding of the antennas on a linear rail. Coherent SAR processing converts the raw data into a complex image. The phase of each image pixel contains information on the target‐sensor distance and can be exploited as a ranging tool. The interferometric technique, based on the comparison between paired and coherent SAR images taken at different times, permits the quantitative extraction of this information, thus allowing the monitoring of the morphological changes. The portable device used in this application was developed by the Joint Research Center, Ispra, Italy, specifically for measurements in the field. It is known as Linear SAR, and it is able to provide 17 GHz measurements with a 2.8 m synthetic aperture. A measurement campaign, lasting about 1 week, was performed between July and August 2000 for monitoring superficial displacements at the Ruinon landslide, a 30 million m3 rockslide in the Italian Alps. Two sequences of interferograms are presented and discussed. The interpretation of the sequences has allowed us to derive multitemporal deformation maps of the test area, thus showing the entire displacement field of those landslide sectors characterized by higher radar reflectivity and coherence. Displacement rates up to 1.2 mm h−1 have been measured with a pixel resolution of 5 m and a measurement precision of 0.75 mm. The results have been validated by using ground truth data obtained through automatic extensometers and topographic measurements. Discrepancies are limited to a few millimeters.

Test and evaluation trials of metal detectors that have been made in recent years have shown the need for common testing specifications so that the results of such trials are useful to the wider demining community. Stemming from initiatives to promote standardization within Humanitarian Mine Action, a CEN Workshop (an "informal" international standardization process) was established to standardize the testing of metal detectors. This has produced a "CEN Workshop Agreement" that gives principles, guidelines and procedures for detector testing. In particular a method for quantifying detection capability has been agreed.

A ground-based synthetic aperture radar (GB-SAR) interferometer is used to retrieve the velocity field of a landslide. High-resolution images are obtained by means of a time domain SAR processor. An in-depth analysis of the sequence of SAR interferograms enables the recognition of a slowly deforming upper scarp in the scene, and a debris flow that feeds the accumulation zone of the landslide, where a fast change in terrain morphology is observed. The estimated deformation map is in agreement with the available measurements obtained by means of Global Positioning System receivers. Results show that GB-SAR interferometry is a cost-effective solution for the monitoring of landslides. The proposed method is shown to be a valid complement to space- and airborne SAR and to the traditional geodetic instruments.

In this paper we have presented a new polarimetric and interferometric approach that can be applied to improve the sub-clutter visibility in de-mining applications. The obtained experimental results have shown that buried plastic mines can not be detected by using only SAR images. However, after applying the method presented here, it is possible to separate the scattering mechanism that is associated with the clutter surface from that corresponding to the mine and estimate their height location. Nevertheless, the success of the proposed method will depend on the geometry of the problem. Indeed, it is necessary the surface clutter to be physically separated from the mine in order to distinguish both scattering mechanisms by optimising the interferometric coherence. It has also been proved that the probability of detection shows a strong dependency on the frequency range. In case of detecting plastic mines, we have seen that it is convenient to operate at low frequencies in order to reduce the attenuation caused by ground propagation. On the other hand, multi-look averaging techniques must be applied in order to reduce the false alarm rate and improve the height estimation accuracy, at the expense of loosing spatial resolution.

A recently developed technique, polarimetric radar interferometry, is applied to tackle the problem of the detection of buried objects embedded in surface clutter. An experiment with a fully polarimetric radar in an anechoic chamber has been carried out using different frequency bands and baselines. The processed results show the ability of this technique to detect buried plastic mines and to measure their depth. This technique enables the detection of plastic mines even if their backscatter response is much lower than that of the surface clutter.

For much of the last century, the degradation of the sea due to ship pollutions has been recognized as a major concern. Early in the thirties, seven major maritime nations proceeded voluntarily to abating measures of oil discharges from tankers. But from then, it took four decades until the international community reaches a widely accepted agreement, namely the MARPOL 73/78 convention. Within a number of regional seas, declared as Special Areas, the regulations are even stricter, prohibiting ship discharges almost totally.To ensure verification, as well as instigation for compliance, effective capabilities for monitoring and intervention are necessary. Key element for successful monitoring however is the regular remote surveillance. To a certain degree this is supported via routine airborne patrol operations, based either on visual inspection or on remote sensors, functioning in the microwave, infrared and ultraviolet spectral regions. Such operations are carried out only over limited geographic areas, since it is not feasible, technically and/or financially, to spread aerial surveillance over the entire breadth of the European waters. As a result, the compliance with the regulations is not applied everywhere with the same care.Satellites equipped with SAR (Synthetic Aperture Radar), due to their capability to detect oil spills on the sea surface, as well as to survey large areas of the sea independently of sunlight and cloud coverage, appear to be ideal for complementing the conventional airborne means. Nevertheless, despite such successful pioneer efforts, many would still argue that the potential of what could be achieved with the spaceborne sAR surveillance, in monitoring illicit vessel discharges, has been somehow oversold.This document concerns exclusively the problem of monitoring ship discharges with spaceborne SAR. We distinguish them from major accidental pollution caused by ships in distress, because the unique singularities of the later pose different requirements for investigation. We present the main results of a regional reconnaissance study carried out over the entire Mediterranean Sea during the year 1999.

An entropy based decomposition technique is applied to some wide-band polarimetric data sets acquired under fully controlled conditions. The measured targets include various tree types and maize plants. The acquired data are analyzed firstly by displaying the loci of the Entropy-Alpha pairs both as a function of the working frequency and the incidence angle. This analysis shows which are the dominant scattering mechanisms of the target as a whole. The decomposition scheme can equally be applied in the time domain. The decomposition results in the time domain show the elements of the sample originating the scattering mechanisms observed in the frequency domain, thus providing useful physical characteristics for constructing equivalent electromagnetic models for further analysis and inversion algorithms. Results show that young and mature maize samples evidence a different relation between the extinction coefficients at different polarizations. Penetration into the samples of maize is high for all frequencies, even at X band. The mature samples can be modeled as a two-layer volume over the ground, whereas the young sample is better represented by one-layer over the ground. On the other hand, the time domain results from a group of young fir trees show the varying penetration depth as a function of frequency, and plots of entropy and average alpha as a function of range also confirm that this target can be modeled as a random volume over the ground.

ERS SAR (Synthetic Aperture Radar) imagery has been used to re-assess the geographical extent of coastal area, which is exposed to environmental impact from Malta’s main sewage outfall at Wied Ghammieq. The outfall presently discharges almost 80% of all the wastewater produced on the island, untreated into the sea. This is carried out through a 716 m long submarine outfall equipped with a terminal diffuser. A number of past short-term field surveys had indicated that the geographical extent of the impacted area may extend up to 8 km south-east of the outfall, especially when the submarine outfall is malfunctioning. SAR imagery, reviewed in the present study, indicates that the geographical extent of the impacted coastline may be in fact three times longer than originally estimated. Support for this suggestion is presented through a review of bathing water quality of areas upstream and downstream to the present outfall.

A measurements campaign aimed to remotely monitoring the stability of a slope, using a ground based interferometric radar equipment, has been concluded. An area of fast movement has been detected and the displacement field has been accurately measured. In addition, the measurements allowed to follow the time evolution of the phenomenon. The, obtained results validate the approach, in the context of critical events over relatively small areas, as a complement to the application of interferometric techniques from space as well as to other traditional tools for ground displacement monitoring.

A coherence optimization method, which makes use of polarimetry to enhance the quality of SAR interferograms, has been experimentally tested under laboratory conditions in an anechoic chamber. By carefully selecting the polarization in both images, the resulting interferogram exhibits an improved coherence above the standard HH or VV channel. This higher coherence produces a lower phase variance, thus estimating the underlying topography more accurately. The potential improvement that this technique provides in the generation of digital elevation models (DEM) of non-vegetated natural surfaces has been observed for the first time on some artificial surfaces created with gravel. An experiment on a true outdoor DEM has not been accomplished yet, but the first laboratory results show that the height error for an almost planar surface can be drastically reduced within a wide range of baselines by using the optimization algorithm. This algorithm leads to three possible interferograms associated with statistically independent scattering mechanisms. The phase difference between those interferograms has been employed for extracting the height of vegetation samples. This retrieval technique has been tested on three different samples: maize, rice, and young fir trees. The inverted heights are compared with ground truth for different frequency bands. The estimates are quite variable with frequency, but their complete physical justification is still in progress. Finally, an alternative simplified scheme for the optimization is proposed. The new approach (called polarization subspace method) yields suboptimum results but is more intuitive and has been used for illustrating the working principle of the original optimization algorithm.

A potential phase unwrapping enhancement by means of a polarimetric coherence optimization is investigated. In particular, the residue density and unwrapped phase after the optimization are compared with the corresponding quantities obtained using single polarization radar data. The study is performed on fully polarimetric data acquired by the portable ground-based system “LISA” developed at the Joint Research Centre

In this paper we suggest the use of the forward-looking geometry with the Radar mounted in the front of a vehicle. In order to assess the feasibility of this measurement geometry, we have performed an extensive series of measurements in an anechoic chamber. Results show that the forward looking geometry is appropriate for the detection of buried landmines.

The application of polarimetric radar interferometry to the estimation of vegetation height is studied. A comparison between different choices for the scattering mechanisms employed in the retrieval algorithm is presented. When applied to crops, the best results are derived from the height difference between interferograms generated at HH+VV and HH-VV polarizations

The Linear SAR (LISA) of the European Microwave Signature Laboratory is presented, A. J. Sieber (1993). The instrument allows two synthetic apertures, one linear synthetic aperture of 5 meters length and another circular aperture allowing a maximum aperture of about 2 meters. The combined use of both apertures allows the creation of 3D radar images. The microwave instrumentation, based on a vector network analyzer allows a dual polarised measurement in a frequency band, ranging from 500 MHz to 6 GHz. By use of an additional frontend, being studied in-house, the usable frequency range can be extended toward higher frequencies, and the usable band of 5.5 GHz can be shifted and a maximum frequency of 20 GHz can be reached. The delivered power of the system is sufficient over the whole bandwidth to see targets in more than 200 meters distance. The recorded radar images have at 100 meters distance a typical resolution of 50 cm and up to 3 cm in cross range. Interferometric mode can be used, to detect either changes of the target or to create digital elevation models of the target. The instrument is controlled by a workstation, that allows also the in field processing of the data. All instruments are hosted by a trailer, which can be easily transported on road

An existing instrumentation radar with 3D capabilities has been modified in order to achieve a more suitable aperture in the z-direction. The aperture being originally circular had as a draw back the fact that objects very soon left the real aperture of the antenna, hence resolution in height was rather poor. A parallelogram shaped arm was invented and implemented with the radar. Due to this technique it was possible to point the antenna over the whole aperture with a constant and adjustable angle with respect to the horizontal plane. The usable aperture has increased very much, hence the resolution increased. The proposed mechanical solution allows also a constant antenna gain for the acquired radar data and shows less problems due to depolarisation, in comparison with other circular apertures. The solution shows very good results, it appears to be an economic way for creation of synthetic aperture radars, that does not require any costly linear positioners. For the simplification of the data processing software, in particular for the SAR-processor, the possibility of not equally placed measurement points has been added to the instrument. This technique avoids interpolation of the data. Many experiments have been performed to validate the system and the implemented SAR processor. Some of these very promising results are presented.