Traditional Selection of Homogeneous Pixels (SHP) methods insufficiently utilize polarization information and rely on extensive statistical computations from large datasets. When applied to mountainous or densely vegetated regions with low coherence, these methods are susceptible to noise interference, which reduces the interpretation reliability. In this study, we propose ViTPolSHP———the Vision Transformer(ViT)-based Polarimetric Synthetic Aperture Radar (PolSAR) Selection of Homogeneous Pixels algorithm for selecting homogeneous pixels in multi-temporal PolSAR imagery. The ViTPolSHP algorithm leverages the temporal average Yamaguchi four-component decomposition features for classification and integrates the terrain characteristics and geometric distortions to derive homogeneous pixel sets even with limited datasets, presenting a promising solution for SAR/InSAR data processing in complex mountainous terrains.

The polarimetric phase optimization method has been integrated into the multitemporal synthetic aperture radar interferometry (MT-InSAR) framework to enhance phase quality and deformation coverage, known as multitemporal polarimetric InSAR (MT-PolInSAR) technology. However, most existing MT-PolInSAR methods optimize phase separately in the temporal and polarimetric dimensions, failing to leverage the interdimensional relationships fully. This article proposes a novel multipolarization optimization method, which achieves one-step phase optimization by joining temporal and polarimetric dimensions based on a joint probability density function and maximum likelihood estimation (MLE). Additionally, a no-threshold regularization is employed to strengthen the stability of the multipolarization covariance matrix. The proposed approach has been validated through synthetic and real quad-polarization datasets. Regarding the real data, ALOS-2/PARSAR-2 from the Fengjie landslide in China and Radarsat-2 data from the Barcelona airport in Spain are used. The experimental outcomes demonstrate that our proposed approach significantly diminishes phase noise while increasing the density of measurement points.

Phase linking is the crucial step in distributed scatterer InSAR processing, which determines the quality of time-series interferometric phases. The weight matrix is the key measure of phase linking method, which controls the participation of each interferometric pair for the single-master phase linking. Existing methods don’t consider the impacts of temporal-changed polarimetric scattering characteristics, leading to large phase closure errors. Based on the polarimetric stationarity, we propose a novel scattering consistency weight measure. Combined with the coherence weight, a joint weight is generated to improve three general phase linking methods. The methods are validated with time-series Radarsat-2 PolSAR data over Kilauea Volcano, Hawaii. The results show that the proposed methods obtain higher temporal posterior coherence and better equivalent single-master (ESM) interferometric phase than traditional methods.

Due to the distinctive side-looking imaging characteristics of Synthetic Aperture Radar (SAR), numerous geometric distortions exist, such as layover, in complex urban scenes, making it challenging to meet interpretation requirements. Synthetic Aperture Radar Tomography (TomoSAR), as a genuine three-dimensional imaging technique, can distinguish discrete targets within the same pixel, and demonstrate significant potential in urban building monitoring. This paper proposes a multi-look tomography method based on homogeneous pixels and a Generalized Likelihood Ratio Test (GLRT), to separate and calculate the height information of scatterers compressed within the same pixel. Experiments were conducted using a dataset from TerraSAR-X in the Beijing region. The results indicate that the proposed method can effectively separate single and multiple scatterers, with a computed building height error not exceeding 1 meter. Additionally, the method is characterized by its simplicity of operation and high processing speed.

Precision agriculture management relies on the delineation of crop field edges. Multi-polarization SAR technology has the ability to penetrate clouds and capture morphological structures or moistures, suited for extracting crop field edges. Due to the time-dependent characteristics and phenological evolutions of crops, the methods with single-date data are difficult to detect complete edges. Moreover, the existing methods fail to extract the dynamic time-varying patterns, limiting the improvement of edge detection accuracy. Based on this, this paper proposes a novel crop field edge detection method based on the time-varying polarimetric characteristics. First, a spatial-temporal homogeneity measure is proposed to pre-identify the edge and homogenous area, for guiding the adaptive calculation of edge strength. Based on the time-series polarimetric stationarity and the trace moment estimation theory, the proposed measure enlarges the separating degree of various crop parcels. Second, a joint edge strength is proposed to enlarge strength contrast between edge and homogenous area. With the spatial-temporal homogeneity measure, it combines the similarity with the root mean square and the similarity with time-series average covariance matrix. Based on the advantages of two kinds of similarities, it highlights the field edges and reduces the impact of speckle noises. Evaluated by 8 quad-polarization and 14 dual-polarization SAR images, the proposed edge detection method achieves better visual presentations and detection accuracies than traditional methods. With the statistics of the signal-noise ratio (SNR), the joint edge strength also has higher strength contrast than conventional strengths. The relevant codes can be found in https://github.com/DawnHanGeo/TSPolEdge.git.

Multiple-aperture interferometric synthetic aperture radar (MAI) technology can obtain the deformation of the surface along the azimuth direction, which makes up for the limitations of traditional interferometric synthetic aperture radar (InSAR) technology. However, the MAI measurement is vulnerable to the ionosphere, which makes the ionospheric delay mixed with the surface deformation, resulting in a serious reduction of the accuracy of the azimuth measurement. In this article, a method for correcting the azimuth ionospheric delay phase is proposed based on the relationship between the ionospheric delay phase and the group phase delay offset, termed by the azimuth group phase delay (AGPD) method. This approach accommodates large-scale deformation fields, facilitating a more comprehensive acquisition of ionospheric information. This method is first employed to reconstruct the coseismic deformation field associated with the 2021 Maduo earthquake. After ionospheric correction, the root mean square errors (RMSEs) between GNSS and MAI measurements decrease from 0.08 to 0.04 m. Then, the results from the Alaska case demonstrate the method’s ability in the identification of intricate ionospheric stripe patterns. Comparative analysis against the existing azimuth ionospheric error correction methods indicates a significant improvement of above 50%.

Change detection (CD) based on time-series PolSAR images is an effective way to analyze land use change in the process of urban change. The deep learning method can extract representative deep features from PolSAR images, but the precise construction of commonly used deep learning models often depends on a large number of training samples. This paper proposes a weak supervised deep learning CD method based on small-scale labeled samples. Using the Unet++ structure and combining semantic information to detect changes, experiments were conducted on two sets of UAVSAR datasets. The results show that the proposed limited labeled samples based Unet++ PolSAR-CD method can effectively detect changes in SAR images under the condition of 40% training samples, which has the best Overall Accuracy (OA), Kappa Coefficient (KC), Precision(Pre), Recall (Rec), and F1-Score, exceeding 0.96, 0.85, 0.89, 0.86, and 0.88 respectively.

The existing exhaustive search polarimetric optimization (ESPO) method exploiting polarimetric diversity has been widely used to improve the phase quality in polarimetric interferometric synthetic aperture radar (PolInSAR). However, the optimization ceiling of the ESPO method based on the coherence metric is largely restricted by the variation of scattering mechanisms in the spatial domain, especially for high-resolution SAR data. To this end, this letter proposes an improved ESPO (ImESPO) method that considers the changes of the scattering mechanisms in local windows and applies it to the time-series phase optimization framework. Both simulated and real experiments demonstrated the effectiveness of the proposed method, which shows that the changes of the scattering mechanisms are more serious in the large window or for high-resolution SAR data. In addition, the effects of the filtering window size and the number of interferograms on optimization were also analyzed in detail.

As a supplement to synthetic aperture radar interferometry (InSAR), multiple-aperture InSAR (MAI) can measure along-track surface deformation, but it is limited by ionospheric path delays, especially with the L- or P-band data. In this letter, we propose a method to correct an ionospheric error in the MAI measurement based on the along-track gradient and 1-D linear fitting. The method depends on the uniqueness of the spatial variation of the along-track gradient of ionospheric error in MAI measurements, which can be well distinguished from other components, such as deformation by using 1-D linear fitting. The method is first evaluated by employing the L-band ALOS-2 PALSAR-2 dataset of the 2019 Ridgecrest earthquake, U.S., and then applied to estimate glacial movements of Grove Mountain, Antarctica, with the ALOS-2 PALSAR-2 dataset.

Isolating the orbital error from the interferometric synthetic aperture radar (InSAR) observations is a great challenge, especially in the presence of tectonic deformation due to their similar spatial patterns. The influence of orbital error is systematic, which can reduce the reliability of deformation monitoring. In this letter, we propose a method to isolate the orbital error from the multitemporal InSAR (MTInSAR) derived tectonic deformation based on the wavelet multiresolution analysis and independent component analysis (ICA). Starting from the sequential interferometric phase of unwrapping, the tectonic deformation and orbital error are firstly extracted from the interferometric phase by wavelet analysis based on their longwavelength spatial patterns, and ICA is then used to isolate the orbital error from the tectonic deformation according to the different temporal characteristics of the two types of signals. In the simulation experiment, the root-mean-square error (RMSE) of the isolated orbital error is 2.6 mm. Experiments with real data in Southern California show that the proposed method can successfully separate the orbital error from the tectonic deformation, and the InSAR deformation rates are in good agreement with the GPS observations.

The objective of this letter is to extend a method proposed by Kweon et al. to retrieve soil moisture (mv) over bare soil surface by combining neighborhood pixels of single-polarization synthetic aperture radar (SAR) data. This letter uses single-polarization (HH, VV) SAR data to simultaneously retrieve the root-mean-square (rms) height (hrms) and the real part of the relative dielectric constant (εs) which can be converted to soil moisture content. For the copolarization SAR data, the letter first uses the Integral Equation Model (IEM) and the semiempirical calibration of the correlation length (L) to obtain the probability distribution curve of rms height and the real part of the relative dielectric constant for each neighborhood pixel. Then, these probability distribution curves are placed on the εs-hrmsplane, and the juxtaposition model is applied to obtain the average value of estimations of neighborhood pixels. The average soil moisture estimations of neighborhood pixels in farmlands are compared with the in-situ measurements with the RMSE equal to 0.036 cm3/cm3and the correlation coefficient equal to 0.84 at VV polarization in the L band, which demonstrates that the proposed method is suitable to invert soil moisture with acceptable accuracy and high resolution. However, volume scattering contribution from crops can decrease the performance of the proposed method.

A general volume scattering model was proposed by Neumannet al. based on anisotropy and orientation randomness, which has been successfully applied to forest parameter retrieval from polarimetric interferometric SAR. A general implementation of the Neumann volume scattering model is designed for fully polarimetric SAR data, incorporating the contributions from the ground level consisting of surface scattering and double-bounce scattering. This combination helps to apply the Neumann volume scattering model to different vegetation scenarios. Based on this, a new parameter inversion framework is developed to estimate the anisotropy and the orientation randomness of the volumetric media, which are expected to be consistent with the ground truth. Meanwhile, the polarimetric information from the ground responses is extracted so that the interaction process between the SAR signals and the ground objects is fully explored. The L-band AIRSAR image covering Flevoland, Netherlands was selected for the experiments. Compared with Neumann decomposition, the parameters estimated by the proposed method can more realistically reflect the canopy scattering characteristics. Moreover, the classification accuracy of crops is effectively improved by the feature parameters obtained by the proposed method.

For repeat-pass interferometric systems, temporal decorrelation (TD) is inevitable and cannot be ignored, and can lead to significant bias in the forest height estimation. The TD random volume over ground (TD + RVoG) model has been found to be a reasonable way to describe the scattering process over forest areas. In this letter, based on the TD + RVoG model, a new forest height estimation method is proposed for use with multibaseline polarimetric synthetic aperture radar interferometry (PolInSAR) data. First, the correlation between the ground-to-volume ratios (GVRs) associated with the different polarizations is parameterized according to the geometric interpretation of the RVoG model. An interferometric pair that is assumed to have no TD is then selected based on the eccentricity of the polarimetric coherence region, and the other interferometric pairs are fitted by the TD + RVoG model. E-synthetic aperture radar (E-SAR)$P$-band PolInSAR data sets affected by TD are used to prove the effectiveness of the proposed method. The experimental results show that the forest height results are improved by 25.90% when compared to the RVoG-based method.

Differential interferometric synthetic aperture radar (DInSAR) has been widely used as one of the most important technologies for determining coseismic deformation. However, DInSAR processing is often perturbed by errors including atmospheric effects and those in topographic models, SAR satellite orbits, and phase unwrapping operation. These nuisance components can degrade the accuracy of the measurements and, therefore, distort the inversion of fault slips especially for moderate earthquakes. We propose in this letter a multitemporal InSAR (MTInSAR) method aiming to accurately determine coseismic deformation. By jointly analyzing a set of preseismic SAR images and one postseismic image, the method allows effective separation of coseismic deformation from topographic and satellite orbital errors deformation based on the distinct spatio-temporal characteristics of the signals. Since the solution is achieved directly from wrapped differential phases, the retrieved deformation is also immune to phase unwrapping errors. The October 6, 2008 Mw 6.3 Dangxiong, China earthquake is studied with the proposed method as an example. The slip inverted, respectively, from the MTInSAR and DInSAR coseismic deformation measurements shows up to 34-cm differences, indicating that the topographic error and inaccurate removal of orbital errors can bias the fault slip inversion.

Homogeneous pixel selection (HPS) plays an important role in the application of multitemporal SAR interferometry. The statistical goodness-of-fit testing of the temporal samples has been widely used for HPS. However, the detection rates of the existing methods are unsatisfactory under small datasets. In this paper, a stacked auto-encoder (SAE) network based method is proposed for the selection of homogeneous pixels under the idea of deep learning image classification, as termed by SAEHPS. The SAE network is used to learn the spatial distribution behavior of the average intensity image. The deep network is trained and tested on different high-resolution SAR datasets of the Hong Kong Airport and the Fuzhou City, and three pixel-wise labels (i.e., high, medium, and low reflections) are regarded as outputs of model learning. The unsupervised training and supervised fine-tuning realize the class prediction. The results show that the SAE can achieve robust accuracies above 90% based on empirically labeled samples, especially in non-architectural areas where the distributed scatterers exist. The SAE results are devoted to the multitemporal PS/DS InSAR approach to identify homogeneous pixels. Both qualitative and quantitative experiments in HPS, phase optimization, and deformation monitoring have demonstrated the superiority of the novel method.

With the increasing amount of synthetic aperture radar (SAR) data with various imaging geometries (at least ascending/descending tracks), it is possible to obtain accurate multi-dimensional (MD) deformation time series with long time span. However, in most cases SAR data of different geometries are un-synchronously acquired over the same region, making it impossible to directly solve the underdetermined observation model (OSM) between the interferometric SAR (InSAR) measurements and the MD deformations. Kalman filter (KF), as one of the most famous dynamic estimators, can obtaina prioriinformation of the unknowns based on the preexisting time series, therefore it can be used to deal with this InSAR underdetermined problem. This article employs the KF to realize the dynamic estimation of MD deformations with short-baseline interferograms. The innovation lies in the establishment of the KF state transition model (STM) and OSM, which aims to make the InSAR monitoring problem better adapt to the KF. Particularly, by assuming a smooth deforming process, existing deformation time series are used to establish the STM and to predict the deformations at current moment. Besides, a strain model (SM) is employed to assist the establishment of the OSM. Simulation and real experiments in the Geysers geothermal field (GGF), U.S. demonstrate that, compared with the state-of-the-art methods, the proposed KF method allows more robust deformation estimation and achieves higher computational efficiency for dynamic estimation.

Interferometric phase optimization is important key processing for ensuring the application performance of interferometric synthetic aperture radar (InSAR) technology. The noise’s standard deviation depends on the number of looks and the coherence magnitude. Usually, the coherence estimation uses statistical averaging with spatial samples to reduce the speckle noise in interferometric phase images. It has been demonstrated that polarization plays a significant role in the variation of interferometric complex coherence. Currently, InSAR technology utilizes polarimetric information to develop the coherence optimization theory for improving the phase quality. However, the observed coherence region in the complex unitary circle is usually biased from the free-noise one due to the finite multilooking effect and the practical scene heterogeneity, which makes the coherence optimization unstable. In contrast, based on the coherence estimation theory, this article proposes taking polarimetric information as the statistical samples for constructing polarimetric InSAR (PolInSAR) total power (TP) coherency matrix and performs a joint polarization-space nonlocal estimation. Simulated and real experimental results demonstrate that the proposed method improves the performance of the interferometric phase optimization in these three aspects compared with traditional coherence optimization, including phase quality improvement, the number of high coherent points, and computational efficiency.

With the launch of various multipolarimetric satellites, many scholars have introduced the persistent scatterer (PS)-oriented polarimetric optimization methods and extended the persistent scatterer interferometry (PSI) method to multipolarimetric data configuration, called polarimetric PSI (PolPSI) technology. Most PolPSI methods mainly take the amplitude dispersion index (ADI) as the optimization criterion and evaluate the temporal amplitude stationarity of each polarimetric channel for finding an optimal one. However, due to the unstable statistical characteristics of the quality indicator, many non-PS pixels are easily mistaken for the PS candidates (PSCs), and the performance of interferometric phase optimization is also limited. To overcome these restrictions, in this article, a novel PolPSI method is proposed based on the following two improved innovations. First, in terms of PSC selection, the trace moment (TM)-based statistical properties of time-series polarimetric coherency matrices are utilized for selecting the scatterers with the temporal polarimetric stationarity. Second, in terms of interferometric phase optimization, all interferometric coherency matrices of multipolarization channels are added up together to construct the total power (TP) interferogram for suppressing the effect of speckle noise and decorrelation. In the experiment, 13 scenes of quad-polarization ALOS PALSAR-1 image are selected to verify the algorithm’s effectiveness. The experimental results demonstrate that the proposed PolPSI method can better improve the deformation monitoring performance in three aspects than both the single-polarimetric HH and traditional exhaustive search polarimetric optimization (ESPO) methods, including phase quality improvement, density of PSs, and computational efficiency.

Estimation of surface deformation using synthetic aperture radar interferometry (InSAR) technique requires a precise removal of the topographic phase. Under multitemporal InSAR (MTInSAR) framework, topographic residual raised by differential operation with external Digital Elevation Model (DEM) is usually parameterized and jointly estimated together with deformation model, while the estimation can be distorted by systematic errors (e.g., model bias, baseline error). This letter aims to offer practical guidelines to users of MTInSAR framework concerning these errors and estimation precision. Starting from the generalized model, we derived the error propagation formula to quantitatively indicate how and to what extent the systematic errors degrade the topographic parameter estimation. The formulas validated by simulated tests are expected to be useful for optimal selection of MTInSAR modeling strategies and development of innovative algorithms (e.g., non-parametric estimator) for retrieval of DEM residuals from MTInSAR measurements.

Phase decorrelation, as one of the main error sources, limits the capability of interferometric synthetic aperture radar (InSAR) for deformation mapping over areas with low coherence. Although several methods have been realized to reduce decorrelation noise, for example, by phase linking and spatial and temporal filters, their performances deteriorate when coherence estimation bias exists. We present an arc-based approach that allows reconstructing unwrapped interval phase time-series based on iterative weighted least squares (WLS) in temporal and spatial domains. The main features of the method are that phase optimization and unwrapping can be jointly conducted by spatial and temporal iterative WLS and coherence matrix bias has negligible effects on the estimation. In addition, the linear formation makes the implementation suitable with small subset of interferograms, providing an efficient solution for future big SAR data. We demonstrate the effectiveness of the proposed method using simulated and real data with different decorrelation mechanisms and compare our approach with the state-of-art phase reconstruction methods. Substantial improvement can be achieved in terms of reduced root-mean-square error (RMSE) in the simulation data and increased density of coherent measurements in the real data.

Deformation monitoring of a converter station of an electrical power transmission system will help to prevent potential damages to power facilities and properties. Corner reflector InSAR (CRInSAR) enables local deformation measurements in low coherence areas like construction-engineering projects. However, the accuracy of CRInSAR will be degraded by the phase unwrapping errors, especially when the deformation is large or dominated by nonlinear component. This letter reports a study that employs CRInSAR technique to monitor the deformations of ten CRs installed in Xiangtan converter station, China, with seven TerraSAR-X Spotlight images. A two-step phase unwrapping tactics is proposed based on the least squares ambiguity decorrelation adjustment (LAMBDA) algorithm to focus on estimating nonlinear deformation without being affected by unwrapping errors. The results reveal that the two-step LAMBDA algorithm can achieve an accuracy of less than 2 mm for CRInSAR deformation monitoring regardless of small- or large-scale deformations, as validated by the trigonometric leveling measurements.

High spatio-temporal resolution deformation series can be used to improve the understanding of deformation mechanism, thereby contributing to prevention and control of geological disasters such as mine subsidence, landslide, and earthquake. Among ground deformation monitoring technologies, global navigation satellite system has high temporal resolution but low spatial resolution, and interferometric synthetic aperture radar (InSAR) has high spatial resolution but low temporal resolution. Fusing these two data may generate high spatio-temporal resolution deformation series. Existing fusion methods usually use the bi-direction interpolation, which does not consider the spatio-temporal cross correlation and is computationally extensive. We propose a dynamic filtering fusion model based on the spatio-temporal random effect (a spatio-temporal Kalman filter) model. Experiments with simulated data and real data from the Los Angeles area are conducted to validate this method. Simulated experimental results are compared with truth data and the Los Angeles experiment data results are verified using the leave-one InSAR image-out validation method. The RMS results for them are around 13.8 and 5 mm, respectively, indicating that the proposed method can achieve high accuracy and high spatial-temporal resolution deformation time series.

Interferometric synthetic aperture radar (InSAR) technique is a proven technique for measuring 3-D surface deformations by combining InSAR measurements from different techniques (i.e., differential InSAR, multiaperture InSAR, and pixel offset-tracking) and different tracks (i.e., ascending and descending) on a pixel-by-pixel basis. However, it is difficult to obtain the exact a priori variances or weights for such different kinds of InSAR measurements, resulting in inaccurate estimations of 3-D deformations. This paper proposes a method to retrieve 3-D deformations with InSAR by integrating the strain model and variance component estimation algorithm, which can exploit the spatial correlation of the adjacent points' deformations and produce accurate weights for multiple InSAR measurements. The proposed method is assessed with both simulated and real data sets. The results have shown that the proposed method can accurately measure 3-D surface deformations associated with geohazards, and even those occurring in a transient or short-term period (e.g., earthquake and volcanic eruption). In the case study of the 2007 eruption of Kilauea Volcano (Hawai'i), improvements of 51.2%, 22.4%, and 18.5% have been achieved for the derived east, north, and up displacements, respectively, with respect to those derived from the classical weighted least squares method.

This paper presents a novel method for modeling and robustly estimating the time-series 3-D mining-induced large displacements from a single imaging geometry (SIG) synthetic aperture radar (SAR) amplitude data set using the offset-tracking (OT) technique (hereafter referred to as the OT-SIG). It first generates multitemporal observations of 3-D mining-induced displacements from the single-geometry SAR amplitude data set with the assistance of a prior model. Then, a functional relationship between mining-induced time-series 3-D displacements and the multitemporal 3-D deformation observations generated is constructed. Finally, the time-series 3-D displacements are robustly estimated based on the constructed function model using the M-estimator. The proposed OT-SIG provides a robust and cost-effective tool for retrieving time-series 3-D mining-induced large displacements, relaxing the basic requirement of the traditional method that at least two different viewing geometries' SAR data are needed. Finally, we tested the proposed OT-SIG with descending TerraSAR-X SAR amplitude data set over the Daliuta coal mining area in China. The results show that the root-mean-square errors (RMSEs) of OT-SIG-estimated time-series displacements are about 0.22 and 0.11 m in the vertical and horizontal directions, respectively. These RMSEs are around 5.7% and 10.9% of the maximum in situ deformation measurements in the corresponding directions, which can meet the accuracy requirements of practical applications.

Measuring 3-D mining-induced displacements is essential to understand mining deformation mechanisms and assess mining-related geohazards. In our previous work, we proposed a method for estimating 3-D mining-induced large displacements with the surface deformation along the radar line-of-sight (LOS) direction derived from a single amplitude pair (SAP) of synthetic aperture radar (SAR) using the offset tracking (OT) procedure (hereafter referred to as OT-SAP). The OT-SAP method effectively reduces the strict requirements on SAR data of the previous OT-based methods for 3-D mining-induced displacement retrieval. However, OT-SAP is not robust to errors in the LOS deformation, due to the lack of redundant observations. In this paper, we present an alternative approach (hereafter called AOT-SAP) to OT-SAP. The AOT-SAP method involves estimating the 3-D mining-induced large displacements with OT-derived 2-D deformation observations along the LOS and azimuth directions from an SAP of SAR, instead of just the LOS deformation in the OT-SAP method. Consequently, more redundant observations are incorporated in the AOT-SAP method compared with the previous OT-SAP method. The theoretical analysis and experiments based on both simulated and real data sets suggest that AOT-SAP can effectively improve the accuracies of the estimated 3-D displacements compared with the OT-SAP-estimated ones.

A new approach is presented for mapping 3-D surface displacement caused by subsurface fluid volumetric change based on 1-D interferometric synthetic aperture radar (InSAR) line-of-sight measurements and surface deformation modeling. The relationship between surface deformation and source fluid volumetric change is modeled according to elastic half-space theory. A distinctive advantage of the proposed approach is that it effectively extends the capability of the sun-synchronous orbit side-looking synthetic aperture radar that has been essentially only able to measure 1-D displacements accurately or at most 2-D displacements when InSAR measurements from more than one orbit or platform are combined. Experimental studies are carried out with both simulated and real data sets to test the performance of the method. The results have demonstrated that the approach works very well.

This paper presents a novel method for estimating the model parameters of the probability integral method (PIM) based on the line-of-sight deformation derived from the interferometric synthetic aperture radar. Then, it applies the settled PIM to forward predict the horizontal and vertical displacements induced by the extraction of a new working panel. The proposed method first constructed the functional relationship between the InSAR-derived LOS deformation and the model parameters of PIM. Subsequently, an improved genetic algorithm (GA), in which gross error elimination was imposed, was proposed, and used to estimate the model parameters of PIM with a large number of LOS deformation measurements. The estimated model parameters and PIM were then employed to forward predict the horizontal and vertical displacements induced by the extraction of a working panel. Simulated experiments show that the rmses of the predicted displacements along the up-down, west-east, and north-south directions are 1.5, 0.9, and 2.5 mm, respectively. Real data experiments over the Qianyingzi coal mining area of China indicate that the predicted displacements are highly consistent with those by field surveys, with rmses of 4.1 and 3 cm for the vertical and horizontal directions, respectively. These imply that the proposed approach can be a very promising tool for predicting the mining-induced displacements and will potentially contribute to the assessing and forecasting of possible geological hazards in the mining area.

Orbital errors, characterized typically as longwavelength artifacts, commonly exist in interferometric synthetic aperture radar (InSAR) imagery as a result of inaccurate determination of the sensor state vector. Orbital errors degrade the precision of multitemporal InSAR products (i.e., ground deformation). Although research on orbital error reduction has been ongoing for nearly two decades and several algorithms for reducing the effect of the errors are already in existence, the errors cannot always be corrected efficiently and reliably. We propose a novel model that is able to jointly estimate deformation rates and orbital errors based on the different spatial-temporal characteristics of the two types of signals. The proposed model is able to isolate a long-wavelength ground motion signal from the orbital error even when the two types of signals exhibit similar spatial patterns. The proposed algorithm is efficient and requires no ground control points. In addition, the method is built upon wrapped phases of interferograms, eliminating the need of phase unwrapping. The performance of the proposed model is validated using both simulated and real data sets. The demo codes of the proposed model are also provided for reference.

A Kalman-filter-based approach is presented for resolving 3-D surface displacements using multisensor, multitrack, and multitemporal interferometric synthetic aperture radar (SAR) measurements. Measurements from each interferogram are projected into the three reference directions and combined in the Kalman filter model with displacements determined from previous interferograms to produce updated displacement measurements. Both simulated and real data sets are used to test the proposed approach. It is found that the method works well when the measurement noise is low. The displacements in the north direction, however, are much lower in accuracy than those in the other two directions and even become unstable when the measurement noise is high due to the polar-orbiting imaging geometries of the current satellite SAR sensors.

Previous approaches that integrate interferometric synthetic aperture radar (InSAR) and GPS measurements for 3-D surface displacement mapping require statistically estimating the variances of the measurements to yield optimal results. We present a variance component estimation approach to weigh the InSAR and GPS measurements in deriving 3-D surface displacements. The approach exploits the observations themselves for determining the weighting scheme, and therefore the a priori information on the stochastic model of the observations is not required. This is of great importance as accurate knowledge on the stochastic model is often unavailable. The performance of the proposed method is validated with both simulated and real datasets.