Karlus A C de Macedo (original) (raw)

Papers by Karlus A C de Macedo

We built and analysed an airborne DInSAR time series of six P-band SAR images acquired every mont... more We built and analysed an airborne DInSAR time series of six P-band SAR images acquired every month over a region in the upper Amazon river basin. After proper residual motion compensation , water level changes under the foliage and terrain movements due to the river dynamics are clearly revealed. The estimations of a non-redundant and redundant network of interferograms are analysed and some consistent water variation measurements with LS residuals < 3cm are obtained.

—Recently some experiments demonstrated that reliable DInSAR measurements can be achieved at any ... more —Recently some experiments demonstrated that reliable DInSAR measurements can be achieved at any band and that further time-series analyses can be applied to airborne data. However , most of the airborne DInSAR results, including the time-series , published so far have focused on short-term analyses (base-lines within hours or few days). This paper presents the first long-term airborne DInSAR survey at P-and X-band with temporal baselines of 1 year and 3 months. The survey was performed by the OrbiSAR system of OrbiSat under contract with Petrobras (PROTRAN), as part of a project to investigate the potential of DInSAR technique to identify, prior to structural damage, geohaz-ards threats to the oil/gas pipelines in São Sebastião—SP, Brazil. After 1 year and 3 months, the P-band data have interferometric coherence equal or greater than 0.3 for approximately 80% of the imaged dense vegetated areas. At X-band, we achieved coherence equal or greater than 0.3 in the urban area. After removing all residual motion errors with proper up-to-date processing, we derived , for the P-band data, land movements with absolute accuracy in the order of centimeters. For X-band we derived land movement measurements with absolute accuracy in the order of millimeters. Through field work evidences, the paper analyses the causes of these centimeter to millimeter land movements, and how they are related to geodynamic processes and geohazard risks. A comparison between the DInSAR and in-loco inclinometer measurements is presented. The paper suggests some possible operational scenarios and discusses on the potential of the airborne DInSAR for geohazard risk monitoring.

—There are basically two methods for retrieving the ground and the canopy height from interferome... more —There are basically two methods for retrieving the ground and the canopy height from interferometric synthetic aperture radar (InSAR) in forested areas. The first method is based on the difference between InSAR height estimations from dual-band (DB) systems, typically operating at X-and P-bands HH. The second method is based on the modeling of the polarimetric (Pol) InSAR response along the forest vertical structure, typically at L-or P-band. This paper proposes the combination of both methods, so that the ground and total tree height estimations are improved and become available alongside the interferometric forest height with the usage of polarimetric data and the RVoG model adoption in both bands. In the proposed method (DB-PolInSAR), first, the ground phase is retrieved from the RVoG inversion through a straightforward line fit of the P-Band polari-metric data in the complex plane. Fixing the ground height coming from the previous P-band inversion and applying the RVoG model to the X-band interferometric data, we estimate the total tree height. Repeat-pass dual-polarimetric (HH and HV) P-band data and single-pass three-baseline HH X-band data acquired with the airborne OrbiSAR sensor of Bradar over the Amazon region of Urucu are used to demonstrate the proposed method. Comparisons between the dual-band PolInSAR and the dual-band single-polarization cases are performed for five different P-band single-baseline configurations. Better ground estimation over range is obtained with the proposed method. Furthermore, the three-antenna single-pass X-band data enabled a robust RVoG total tree height inversion.

To allow time-series analysis of airborne SAR images using PSs (Permanent Scatterers), this paper... more To allow time-series analysis of airborne SAR images using PSs (Permanent Scatterers), this paper has two main objectives. The first is to show, in a quantitative way, that there is a compromise between the number of images used to detect PSs, their probability of being detected and their stability. This tradeoff is derived based on estimation and detection theories. The second objective is to investigate the possibility of the use of permanent scatterers to estimate undesired phase undulations in airborne data due to residual motion errors. A new technique is proposed, the so-called PS-PGA, where we apply the Phase Gradient algorithm on the PSs in order to obtain sub-wavelength estimations of residual motion errors for both master and slaves, separately, differently from current approaches. Compensation of these residual errors will lead to more reliable airborne D-InSAR measurements.

In a large number of scenarios and missions, the technical, operational and economical advantages... more In a large number of scenarios and missions, the technical, operational and economical advantages of UAS-based photogrammetry and remote sensing over traditional airborne and satellite platforms are apparent. Airborne Synthetic Aperture Radar (SAR) or combined optical/SAR operation in remote areas might be a case of a typical "dull, dirty, dangerous" mission suitable for unmanned operation -in harsh environments such as for example rain forest areas in Brazil, topographic mapping of small to medium sparsely inhabited remote areas with UAS-based photogrammetry and remote sensing seems to be a reasonable paradigm.

2011 IEEE International Geoscience and Remote Sensing Symposium, 2011

Recently, some experiments demonstrated that reliable DIn-SAR measurements can be achieved at any... more Recently, some experiments demonstrated that reliable DIn-SAR measurements can be achieved at any band and that further time-series analyses can be applied for airborne data. However, most of the airborne DInSAR results, including the time-series, published so far have focused on short-term analyses (baselines within hours or few days). This paper presents the first worldwide airborne DInSAR survey at P-and X-band for measuring the land movements occurred within 1 year and 3 months. The survey was performed by the OrbiSAR system of OrbiSat under contract with Petrobras (CENPES), as part of a experiment with the objective to identify possible threats to the pipeline due to land movements in São Sebastião-SP, Brazil. The measurements at P-band show reliable and coherent movements in 80% of the imaged vegetated areas with accuracy in the order of centimeters. At X-band we were able to reliably measure coherent movements in urban areas with accuracy in the order of millimeters. Through field work evidences, the paper analyses the causes of these small scale land movements, and how they are related to geodynamic processes. A comparison between the DInSAR and in-loco inclinometer measurements is presented. The paper suggests some possible operational scenarios and discusses on the potential of the airborne DInSAR for land movement monitoring.

This paper presents the results of a controlled experiment performed with the E-SAR airborne syst... more This paper presents the results of a controlled experiment performed with the E-SAR airborne system to measure the centimeter movement of three corner reflectors with known positions and displacements. The objective of this work is to evaluate the potential of the actual E-SAR airborne system for D-InSAR applications and the accuracy of the implemented D-InSAR processing chain. An approach for the generation of differential interferograms using two interferograms and a DEM is presented. The images are from the Oberpfaffenhofen test site and they were acquired in September 02, 2003 in L and C-band.

Joint Urban Remote Sensing Event 2013, 2013

ABSTRACT The paper addresses the analysis of high resolution interferograms relevant to urban are... more ABSTRACT The paper addresses the analysis of high resolution interferograms relevant to urban areas and achieved by means of the X-band OrbiSAR system. The OrbiSAR system is an airborne SAR sensor capable of acquiring single pass and repeat pass interferometric SAR data at very high resolution. Such a system is thus capable of providing very appealing single-pass and repeat-pass interferometric data-sets characterized by high resolution. In this work, two data-sets, acquired over the urbanized cities of São José dos Campos and São Sebastião-SP, Brazil, will be analyzed with a twofold aim: first, to provide insight for the retrieval of high accuracy DEM on urbanized areas, second to show some results obtainable with the airborne Differential SAR Interferometry technique over urban areas.

This paper presents the very first assessment of the permanent scatterer (PS) technique for airbo... more This paper presents the very first assessment of the permanent scatterer (PS) technique for airborne data. A data set of 14 SAR images at L-band, acquired over the Oberpfaffenhofen area on the same day with the E-SAR system of the German Aerospace Center (DLR), is used for the first airborne time series analysis with PS. The paper shows the importance of mitigating the residual motion errors through the use of precise motion compensation strategy before PS analysis. The target velocity and DEM error results are obtained by a periodogram-based estimation considering the linear displacement model. Due to the small number of images in our data set, the displacement velocity and DEM error results are presented on a PS basis. Target structures related to selected reliable PSs are shown and the corresponding periodograms highlighted.

IEEE Transactions on Geoscience and Remote Sensing, 2000

Airborne repeat-pass SAR systems are very sensible to subwavelength deviations from the reference... more Airborne repeat-pass SAR systems are very sensible to subwavelength deviations from the reference track. To enable repeat-pass interferometry, a high-precision navigation system is needed. Due to the limit of accuracy of such systems, deviations in the order of centimeters remain between the real track and the processed one, causing mainly undesirable phase undulations and misregistration in the interferograms, referred to as residual motion errors. Up to now, only interferometric approaches, as multisquint, are used to compensate for such residual errors. In this paper, we present for the first time the use of the autofocus technique for residual motion errors in the repeat-pass interferometric context. A very robust autofocus technique has to be used to cope with the demands of the repeat-pass applications. We propose a new robust autofocus algorithm based on the weighted least squares phase estimation and the phase curvature autofocus (PCA) extended to the range-dependent case. We call this new algorithm weighted PCA. Different from multisquint, the autofocus approach has the advantage of being able to estimate motion deviations independently, leading to better focused data and correct impulse-response positioning. As a consequence, better coherence and interferometric-phase accuracy are achieved. Repeat-pass interferometry based only on image processing gains in robustness and reliability, since its performance does not deteriorate with time decorrelation and no assumptions need to be made on the interferometric phase. Repeat-pass data of the E-SAR system of the German Aerospace Center (DLR) are used to demonstrate the performance of the proposed approach.

IEEE Geoscience and Remote Sensing Letters, 2005

Efficient synthetic aperture radar (SAR) processing algorithms are unable to exactly implement th... more Efficient synthetic aperture radar (SAR) processing algorithms are unable to exactly implement the aperture-and topography-dependent motion compensation due to the superposition of the synthetic apertures of several targets having different motion errors and potentially different topographic heights. Thus, during motion compensation, a reference level is assumed, resulting in residual phase errors that impact the focusing, geometric fidelity, and phase accuracy of the processed SAR images. This letter proposes a new short fast Fourier transform-based postprocessing methodology capable of efficient and precise compensation of these topography-and aperture-dependent residual phase errors. In addition to wide beamwidth (very high resolution) SAR systems, airborne repeat-pass interferometry especially benefits from this approach, as motion compensation can be significantly improved, especially in areas with high topographic changes. Repeat-pass interferometric data of the E-SAR system of the German Aerospace Center (DLR) are used to demonstrate the performance of the proposed approach.

2009 IEEE International Geoscience and Remote Sensing Symposium, 2009

This paper presents the interferometric airborne repeat-pass mode results at X-band after applyin... more This paper presents the interferometric airborne repeat-pass mode results at X-band after applying a complete residual motion compensation (MoCo) strategy. The data were acquired, over the Perugia area, Italy, by the OrbiSAR sensor from OrbiSat, Brazil, and the first X-Band D-InSAR results were published, where a space-invariant topographydependent MoCo was applied after focusing with smoothed elevation model. Now, in this paper, we apply to the same X-band data the precise topography-and aperture-dependent (PTA) MoCo and the weighted phase curvature autofocus (WPCA) to account for high-order residual motion errors. We compare the differential interferograms and coherence map obtained after PTA-WPCA to the formerly results. The results show improvement in the interferometric accuracy after PTA-WPCA processing. The need of such complete processing chain for narrowband systems is discussed.

We built and analysed an airborne DInSAR time series of six P-band SAR images acquired every mont... more We built and analysed an airborne DInSAR time series of six P-band SAR images acquired every month over a region in the upper Amazon river basin. After proper residual motion compensation , water level changes under the foliage and terrain movements due to the river dynamics are clearly revealed. The estimations of a non-redundant and redundant network of interferograms are analysed and some consistent water variation measurements with LS residuals < 3cm are obtained.

—Recently some experiments demonstrated that reliable DInSAR measurements can be achieved at any ... more —Recently some experiments demonstrated that reliable DInSAR measurements can be achieved at any band and that further time-series analyses can be applied to airborne data. However , most of the airborne DInSAR results, including the time-series , published so far have focused on short-term analyses (base-lines within hours or few days). This paper presents the first long-term airborne DInSAR survey at P-and X-band with temporal baselines of 1 year and 3 months. The survey was performed by the OrbiSAR system of OrbiSat under contract with Petrobras (PROTRAN), as part of a project to investigate the potential of DInSAR technique to identify, prior to structural damage, geohaz-ards threats to the oil/gas pipelines in São Sebastião—SP, Brazil. After 1 year and 3 months, the P-band data have interferometric coherence equal or greater than 0.3 for approximately 80% of the imaged dense vegetated areas. At X-band, we achieved coherence equal or greater than 0.3 in the urban area. After removing all residual motion errors with proper up-to-date processing, we derived , for the P-band data, land movements with absolute accuracy in the order of centimeters. For X-band we derived land movement measurements with absolute accuracy in the order of millimeters. Through field work evidences, the paper analyses the causes of these centimeter to millimeter land movements, and how they are related to geodynamic processes and geohazard risks. A comparison between the DInSAR and in-loco inclinometer measurements is presented. The paper suggests some possible operational scenarios and discusses on the potential of the airborne DInSAR for geohazard risk monitoring.

—There are basically two methods for retrieving the ground and the canopy height from interferome... more —There are basically two methods for retrieving the ground and the canopy height from interferometric synthetic aperture radar (InSAR) in forested areas. The first method is based on the difference between InSAR height estimations from dual-band (DB) systems, typically operating at X-and P-bands HH. The second method is based on the modeling of the polarimetric (Pol) InSAR response along the forest vertical structure, typically at L-or P-band. This paper proposes the combination of both methods, so that the ground and total tree height estimations are improved and become available alongside the interferometric forest height with the usage of polarimetric data and the RVoG model adoption in both bands. In the proposed method (DB-PolInSAR), first, the ground phase is retrieved from the RVoG inversion through a straightforward line fit of the P-Band polari-metric data in the complex plane. Fixing the ground height coming from the previous P-band inversion and applying the RVoG model to the X-band interferometric data, we estimate the total tree height. Repeat-pass dual-polarimetric (HH and HV) P-band data and single-pass three-baseline HH X-band data acquired with the airborne OrbiSAR sensor of Bradar over the Amazon region of Urucu are used to demonstrate the proposed method. Comparisons between the dual-band PolInSAR and the dual-band single-polarization cases are performed for five different P-band single-baseline configurations. Better ground estimation over range is obtained with the proposed method. Furthermore, the three-antenna single-pass X-band data enabled a robust RVoG total tree height inversion.

To allow time-series analysis of airborne SAR images using PSs (Permanent Scatterers), this paper... more To allow time-series analysis of airborne SAR images using PSs (Permanent Scatterers), this paper has two main objectives. The first is to show, in a quantitative way, that there is a compromise between the number of images used to detect PSs, their probability of being detected and their stability. This tradeoff is derived based on estimation and detection theories. The second objective is to investigate the possibility of the use of permanent scatterers to estimate undesired phase undulations in airborne data due to residual motion errors. A new technique is proposed, the so-called PS-PGA, where we apply the Phase Gradient algorithm on the PSs in order to obtain sub-wavelength estimations of residual motion errors for both master and slaves, separately, differently from current approaches. Compensation of these residual errors will lead to more reliable airborne D-InSAR measurements.

In a large number of scenarios and missions, the technical, operational and economical advantages... more In a large number of scenarios and missions, the technical, operational and economical advantages of UAS-based photogrammetry and remote sensing over traditional airborne and satellite platforms are apparent. Airborne Synthetic Aperture Radar (SAR) or combined optical/SAR operation in remote areas might be a case of a typical "dull, dirty, dangerous" mission suitable for unmanned operation -in harsh environments such as for example rain forest areas in Brazil, topographic mapping of small to medium sparsely inhabited remote areas with UAS-based photogrammetry and remote sensing seems to be a reasonable paradigm.

2011 IEEE International Geoscience and Remote Sensing Symposium, 2011

Recently, some experiments demonstrated that reliable DIn-SAR measurements can be achieved at any... more Recently, some experiments demonstrated that reliable DIn-SAR measurements can be achieved at any band and that further time-series analyses can be applied for airborne data. However, most of the airborne DInSAR results, including the time-series, published so far have focused on short-term analyses (baselines within hours or few days). This paper presents the first worldwide airborne DInSAR survey at P-and X-band for measuring the land movements occurred within 1 year and 3 months. The survey was performed by the OrbiSAR system of OrbiSat under contract with Petrobras (CENPES), as part of a experiment with the objective to identify possible threats to the pipeline due to land movements in São Sebastião-SP, Brazil. The measurements at P-band show reliable and coherent movements in 80% of the imaged vegetated areas with accuracy in the order of centimeters. At X-band we were able to reliably measure coherent movements in urban areas with accuracy in the order of millimeters. Through field work evidences, the paper analyses the causes of these small scale land movements, and how they are related to geodynamic processes. A comparison between the DInSAR and in-loco inclinometer measurements is presented. The paper suggests some possible operational scenarios and discusses on the potential of the airborne DInSAR for land movement monitoring.

This paper presents the results of a controlled experiment performed with the E-SAR airborne syst... more This paper presents the results of a controlled experiment performed with the E-SAR airborne system to measure the centimeter movement of three corner reflectors with known positions and displacements. The objective of this work is to evaluate the potential of the actual E-SAR airborne system for D-InSAR applications and the accuracy of the implemented D-InSAR processing chain. An approach for the generation of differential interferograms using two interferograms and a DEM is presented. The images are from the Oberpfaffenhofen test site and they were acquired in September 02, 2003 in L and C-band.

Joint Urban Remote Sensing Event 2013, 2013

ABSTRACT The paper addresses the analysis of high resolution interferograms relevant to urban are... more ABSTRACT The paper addresses the analysis of high resolution interferograms relevant to urban areas and achieved by means of the X-band OrbiSAR system. The OrbiSAR system is an airborne SAR sensor capable of acquiring single pass and repeat pass interferometric SAR data at very high resolution. Such a system is thus capable of providing very appealing single-pass and repeat-pass interferometric data-sets characterized by high resolution. In this work, two data-sets, acquired over the urbanized cities of São José dos Campos and São Sebastião-SP, Brazil, will be analyzed with a twofold aim: first, to provide insight for the retrieval of high accuracy DEM on urbanized areas, second to show some results obtainable with the airborne Differential SAR Interferometry technique over urban areas.

This paper presents the very first assessment of the permanent scatterer (PS) technique for airbo... more This paper presents the very first assessment of the permanent scatterer (PS) technique for airborne data. A data set of 14 SAR images at L-band, acquired over the Oberpfaffenhofen area on the same day with the E-SAR system of the German Aerospace Center (DLR), is used for the first airborne time series analysis with PS. The paper shows the importance of mitigating the residual motion errors through the use of precise motion compensation strategy before PS analysis. The target velocity and DEM error results are obtained by a periodogram-based estimation considering the linear displacement model. Due to the small number of images in our data set, the displacement velocity and DEM error results are presented on a PS basis. Target structures related to selected reliable PSs are shown and the corresponding periodograms highlighted.

IEEE Transactions on Geoscience and Remote Sensing, 2000

Airborne repeat-pass SAR systems are very sensible to subwavelength deviations from the reference... more Airborne repeat-pass SAR systems are very sensible to subwavelength deviations from the reference track. To enable repeat-pass interferometry, a high-precision navigation system is needed. Due to the limit of accuracy of such systems, deviations in the order of centimeters remain between the real track and the processed one, causing mainly undesirable phase undulations and misregistration in the interferograms, referred to as residual motion errors. Up to now, only interferometric approaches, as multisquint, are used to compensate for such residual errors. In this paper, we present for the first time the use of the autofocus technique for residual motion errors in the repeat-pass interferometric context. A very robust autofocus technique has to be used to cope with the demands of the repeat-pass applications. We propose a new robust autofocus algorithm based on the weighted least squares phase estimation and the phase curvature autofocus (PCA) extended to the range-dependent case. We call this new algorithm weighted PCA. Different from multisquint, the autofocus approach has the advantage of being able to estimate motion deviations independently, leading to better focused data and correct impulse-response positioning. As a consequence, better coherence and interferometric-phase accuracy are achieved. Repeat-pass interferometry based only on image processing gains in robustness and reliability, since its performance does not deteriorate with time decorrelation and no assumptions need to be made on the interferometric phase. Repeat-pass data of the E-SAR system of the German Aerospace Center (DLR) are used to demonstrate the performance of the proposed approach.

IEEE Geoscience and Remote Sensing Letters, 2005

Efficient synthetic aperture radar (SAR) processing algorithms are unable to exactly implement th... more Efficient synthetic aperture radar (SAR) processing algorithms are unable to exactly implement the aperture-and topography-dependent motion compensation due to the superposition of the synthetic apertures of several targets having different motion errors and potentially different topographic heights. Thus, during motion compensation, a reference level is assumed, resulting in residual phase errors that impact the focusing, geometric fidelity, and phase accuracy of the processed SAR images. This letter proposes a new short fast Fourier transform-based postprocessing methodology capable of efficient and precise compensation of these topography-and aperture-dependent residual phase errors. In addition to wide beamwidth (very high resolution) SAR systems, airborne repeat-pass interferometry especially benefits from this approach, as motion compensation can be significantly improved, especially in areas with high topographic changes. Repeat-pass interferometric data of the E-SAR system of the German Aerospace Center (DLR) are used to demonstrate the performance of the proposed approach.

2009 IEEE International Geoscience and Remote Sensing Symposium, 2009

This paper presents the interferometric airborne repeat-pass mode results at X-band after applyin... more This paper presents the interferometric airborne repeat-pass mode results at X-band after applying a complete residual motion compensation (MoCo) strategy. The data were acquired, over the Perugia area, Italy, by the OrbiSAR sensor from OrbiSat, Brazil, and the first X-Band D-InSAR results were published, where a space-invariant topographydependent MoCo was applied after focusing with smoothed elevation model. Now, in this paper, we apply to the same X-band data the precise topography-and aperture-dependent (PTA) MoCo and the weighted phase curvature autofocus (WPCA) to account for high-order residual motion errors. We compare the differential interferograms and coherence map obtained after PTA-WPCA to the formerly results. The results show improvement in the interferometric accuracy after PTA-WPCA processing. The need of such complete processing chain for narrowband systems is discussed.