Spatial Baseline Research Articles

On the Accuracy of Topographic Residuals Retrieved by MTInSAR

Topographic residuals in differential interferometric synthetic aperture radar (InSAR) measurements are mainly caused by inaccurate external digital elevation model (DEM). Accurate separation of the phase component contributed by topographic residuals plays an important role in the retrieval of deformation time series from InSAR observations. Even though the residuals can be modeled and estimated in the framework of multitemporal SAR interferometry (MTInSAR), it is not clear what an optimal processing strategy is and how accurate the estimation can reach. We analyze here the factors that affect the accuracy of the retrieved DEM residuals by applying four commonly used MTInSAR methods in a series of simulated scenarios. The results indicate that besides the quality of interferometric observations, the thresholds of spatial and temporal baselines, the diversity of spatial baseline lengths, the connectivity of interferogram network, and improper deformation model also fluctuate the accuracy of the retrieved topographic residuals. According to these affecting factors, this paper sheds light on an optimal approach to reliably retrieve accurate topographic residuals under MTInSAR framework.

Spatio-Temporal Error Sources Analysis and Accuracy Improvement in Landsat 8 Image Ground Displacement Measurements

Because of the advantages of low cost, large coverage and short revisit cycle, Landsat 8 images have been widely applied to monitor earth surface movements. However, there are few systematic studies considering the error source characteristics or the improvement of the deformation field accuracy obtained by Landsat 8 image. In this study, we utilize the 2013 Mw 7.7 Balochistan, Pakistan earthquake to analyze error spatio-temporal characteristics and elaborate how to mitigate error sources in the deformation field extracted from multi-temporal Landsat 8 images. We found that the stripe artifacts and the topographic shadowing artifacts are two major error components in the deformation field, which currently lack overall understanding and an effective mitigation strategy. For the stripe artifacts, we propose a small spatial baseline (<200 m) method to avoid the stripe artifacts effect on the deformation field. We also propose a small radiometric baseline method to reduce the topographic shadowing artifacts and radiometric decorrelation noises. Those performances and accuracy evaluation show that these two methods are effective in improving the precision of deformation field. This study provides the possibility to detect subtle ground movement with higher precision caused by earthquake, melting glaciers, landslides, etc., with Landsat 8 images. It is also a good reference for error source analysis and corrections in deformation field extracted from other optical satellite images.

Retrieval of agricultural crop height from space: A comparison of SAR techniques

This paper deals with the retrieval of agricultural crop height from space by using multipolarization Synthetic Aperture Radar (SAR) images. Coherent and incoherent crop height estimation methods are discussed for the first time with a unique TanDEM-X dataset acquired over rice cultivation areas. Indeed, with its polarimetric and interferometric capabilities, the TanDEM-X mission enables the tracking of crop height through interferometric SAR (InSAR), polarimetric interferometric SAR (PolInSAR) and the inversion of radiative transfer-based backscattering model. The paper evaluates the three aforementioned techniques simultaneously with a data set acquired in September 2014 and 2015 over rice fields in Turkey during their reproductive stage. The assessment of the absolute height accuracy and the limitations of the approaches are provided. In-situ measurements conducted in the same cultivation periods are used for validation purposes. The PolInSAR and morphological backscattering model results showed better performance with low RMSEs (12 and 13 cm) compared to the differential InSAR result having RMSE of 18 cm. The spatial baseline, i.e. the distance between satellites, is a key parameter for coherent methods such as InSAR and PolInSAR. Its effect on the absolute height accuracy is discussed using TanDEM-X pairs separated by a baseline of 101.7m and 932m. Although the InSAR based approach is demonstrated to provide sufficient crop height accuracy, the availability of a precise vegetation-free digital elevation model and a structurally dense crop are basic requirements for achieving high accuracy. The PolInSAR approach provides reliable crop height estimation if the spatial baseline is large enough for the inversion. The impact of increasing spatial baseline on the absolute accuracy of the crop height estimation is evident for both methods. However, PolInSAR is more cost-efficient, e.g. there is no need for phase unwrapping and any external vegetation free surface elevation data. Instead, the usage of radiative transfer based backscattering models provides not only crop height but also other biophysical properties of the crops with consistent accuracy. The efficient retrieval of crop height with backscattering model is achieved by metamodelling, which makes the computational cost of backscattering inversion comparable to the ones of the coherent methods. However, effectiveness depends on not only the backscattering model, but also the integration of agronomic crop growth rules. Motivated by these results, a combination of backscattering and PolInSAR inversion models would provide a successful method of future precision farming studies.

Multi-temporal SAR observations of the Surat Basin in Australia for deformation scenario evaluation associated with man-made interactions

Human activities for extracting natural resources, may lead to subsequent gradual or abrupt surface deformation, with adverse effects in the local ecosystem and damage to man-made structures. Over the past two decades, interferometric SAR (InSAR) has been demonstrated as the optimal remote sensing technique to estimate surface deformation with high spatial coverage and vertical accuracy over traditional surveying methods. In this paper, the outcome of advanced differential InSAR processing to detect and analyze ground surface behavior due to man-made interactions are presented. An improvement was achieved in the temporal resolution and accuracy using a unique combination of both C-band and L-band SAR satellite acquisitions with different temporal and spatial baselines. The two alternate DInSAR methodologies were applied on the northeastern part of the Surat Basin, Australia for an area without long-term ground-based geodetic observations. The regions undergoing downward motion are located above coal seam gas (CSG) mining sites with rates up to 28 mm/year. Three scenarios were identified: (1) extensive groundwater extraction from shallow aquifers due to CSG mining, (2) CSG mining without direct impact on groundwater resources and (3) patchy uplift over an industrial forest adjacent to a CSG mining district. Contrary to a previous study conducted in this region using the PSInSAR™ technique which reported stability of the area with insignificant surface deformation, this study shows that there are considerable deformation signals consistent with resource extraction. Consequently, it is shown that the SBAS approach is superior to PSInSAR™ for deformation monitoring with focusing on naturally distributed scatterers.

Forest Height Estimation by Means of Pol-InSAR Data Inversion: The Role of the Vertical Wavenumber

This paper examines the multifaceted effect of the effective spatial baseline, as expressed through the vertical (interferometric) wavenumber, on the inversion of forest height from polarimetric interferometric synthetic aperture radar (Pol-InSAR) data. First, the role of the vertical wavenumber in relating forest height to the interferometric (volume) coherence is introduced. Through the review of the forest height inversion from Pol-InSAR data, the effect of the vertical wavenumber on the inversion performance is evaluated. The selection of optimum with respect to forest height inversion performance, vertical wavenumbers is discussed. The impact of the acquisition geometry and terrain slopes on the vertical wavenumber and their consideration in the inversion methodology is addressed. The individual effects discussed are demonstrated by means of airborne repeat pass Pol-InSAR acquisitions in L- and P-band acquired over different forest conditions, including a boreal, a temperate, and a tropical forest test site. The achieved forest height inversion performance is validated against reference height data derived from airborne LIDAR acquisitions.

Accurate Determination of Glacier Surface Velocity Fields with a DEM-Assisted Pixel-Tracking Technique from SAR Imagery

We obtained accurate, detailed motion distribution of glaciers in Central Asia by applying digital elevation model (DEM) assisted pixel-tracking method to L-band synthetic aperture radar imagery. The paper firstly introduces and analyzes each component of the offset field briefly, and then describes the method used to efficiently and precisely compensate the topography-related offset caused by the large spatial baseline and rugged terrain with the help of DEM. The results indicate that the rugged topography not only forms the complex shapes of glaciers, but also affects the glacier velocity estimation, especially with large spatial baseline. The maximum velocity, 0.85 m∙d−1, was observed in the middle part on the Fedchenko Glacier, which is the world’s longest mountain glacier. The motion fluctuation on its main trunk is apparently influenced by mass flowing in from tributaries, as well as angles between tributaries and the main stream. The approach presented in this paper was proved to be highly appropriate for monitoring glacier motion and will provide valuable sensitive indicators of current and future climate change for environmental analysis.

Coastal Upwelling Drives Intertidal Assemblage Structure and Trophic Ecology.

Similar environmental driving forces can produce similarity among geographically distant ecosystems. Coastal oceanic upwelling, for example, has been associated with elevated biomass and abundance patterns of certain functional groups, e.g., corticated macroalgae. In the upwelling system of Northern Chile, we examined measures of intertidal macrobenthic composition, structure and trophic ecology across eighteen shores varying in their proximity to two coastal upwelling centres, in a hierarchical sampling design (spatial scales of >1 and >10 km). The influence of coastal upwelling on intertidal communities was confirmed by the stable isotope values (δ13C and δ15N) of consumers, including a dominant suspension feeder, grazers, and their putative resources of POM, epilithic biofilm, and macroalgae. We highlight the utility of muscle δ15N from the suspension feeding mussel, Perumytilus purpuratus, as a proxy for upwelling, supported by satellite data and previous studies. Where possible, we used corrections for broader-scale trends, spatial autocorrelation, ontogenetic dietary shifts and spatial baseline isotopic variation prior to analysis. Our results showed macroalgal assemblage composition, and benthic consumer assemblage structure, varied significantly with the intertidal influence of coastal upwelling, especially contrasting bays and coastal headlands. Coastal topography also separated differences in consumer resource use. This suggested that coastal upwelling, itself driven by coastline topography, influences intertidal communities by advecting nearshore phytoplankton populations offshore and cooling coastal water temperatures. We recommend the isotopic values of benthic organisms, specifically long-lived suspension feeders, as in situ alternatives to offshore measurements of upwelling influence.

Where is also about time: A location-distortion model to improve reverse geocoding using behavior-driven temporal semantic signatures

While geocoding returns coordinates for a full or partial address, the converse process of reverse geocoding maps coordinates to a set of candidate place identifiers such as addresses or toponyms. For example, numerous Web APIs map geographic point coordinates, e.g., from a user’s smartphone, to an ordered set of nearby Places Of Interest (POI). Typically, these services return the k nearest POI within a certain radius and measure distance to order the results. Reverse geocoding is a crucial task for many applications and research questions as it translates between spatial and platial views on geographic location. What makes this process difficult is the uncertainty of the queried location and of the point features used to represent places. Even if both could be determined with a high level of accuracy, it would still be unclear how to map a smartphone’s GPS fix to one of many possible places in a multi-story building or a shopping mall. In this work, we break up the dependency on space alone by introducing time as a second variable for reverse geocoding. We mine the geosocial behavior of users of online location-based social networks to extract temporal semantic signatures. In analogy to the notion of scale distortion in cartography, we present a model that uses these signatures to distort the location of POI relative to the query location and time, thereby reordering the set of potentially matching places. We demonstrate the strengths of our method by evaluating it against a purely spatial baseline by determining the Mean Reciprocal Rank and the normalized Discounted Cumulative Gain. Our method performs substantially better than said baseline.

Two-sided long baseline radargrammetry from ascending-descending orbits with application to mapping post-seismic topography in the west Sichuan foreland basin

One-sided ascending or descending Synthetic Aperture Radar (SAR) stereo-radargrammetry has limited accuracy of topographic mapping due to the short spatial baseline (~100 km) and small intersection angle. In order to improve the performance and reliability of generating digital elevation model (DEM) from spaceborne SAR radargrammetry, an exploration of two-sided stereo-radargrammetry from the combination of ascending and descending orbits with geometric configuration of long spatial baseline (~1000 km) was conducted in this study. The slant-range geometry between SAR sensors to the earth surface and the Doppler positioning equations were employed to establish the stereoscopic intersection model. The measurement uncertainty of two-sided radargrammetric elevation was estimated on the basis of radar parallax of homogeneous points between input SAR images. Two stereo-pairs of ALOS/PALSAR (Advanced Land Observing Satellite/Phased Array type L-band Synthetic Aperture Radar) acquisitions with the orbital separation almost 1080 km over the west Sichuan foreland basin with rolling topography in southwestern China were employed in the study to obtain the up-to-date terrain data after the 2008 Wenchuan earthquake that hit this area. The quantitative accuracy assessment of two-sided radargrammetric DEM was performed with reference to field GPS observations. The experimental results show that the elevation accuracy reaches 5.5 m without ground control points (GCPs) used, and the accuracy is further improved to 1.5 m with only one GPS GCP used as the least constraint. The theoretical analysis and testing results demonstrate that the two-sided long baseline SAR radargrammetry from the ascending and descending orbits can be a very promising technical alternative for large-area and high accuracy topographic mapping.

Detecting Subsidence in Coastal Areas by Ultrashort-Baseline TCPInSAR on the Time Series of High-Resolution TerraSAR-X Images

In this paper, we present an improved approach of the multitemporal interferometric synthetic aperture radar (InSAR) for detecting land subsidence in coastal areas by using the time series of high-resolution SAR images. In particular, our algorithm extends the capability of the temporarily coherent point InSAR (TCPInSAR) technique that can be used to detect subsidence even in the case of a small number of SAR images available for a study area. The proposed approach is implemented by using the interferograms with ultrashort spatial baselines (USBs) through several procedures, including the selection of USB interferometric pairs, TCP identification, TCP networking and modeling, as well as TCP solution by a least squares estimator. As the topographic effects in coastal areas are negligible in the USB interferograms, an external digital elevation model is no longer necessary for differential processing, thus simplifying both TCP modeling and parameter estimating. The USB-based TCPInSAR algorithm has been tested with the high-resolution TerraSAR-X images acquired over Tianjin (close to Bohai Bay) in China, and validated by using the ground-based leveling measurements. The testing results indicate that the density and coverage extent of TCPs can be increased dramatically by using the proposed algorithm, and the quality of subsidence measurements derived by the USB-based TCPInSAR can be raised.

Detecting Subsidence Along a High Speed Railway by Ultrashort Baseline TCP-InSAR with High Resolution Images

Abstract. A High Speed Railway goes across Wuqing district of Tianjin, China. Historical studies showed that the land subsidence of this area was very serious, which would give rise to huge security risk to the high speed railway. For detecting the detailed subsidence related to the high speed railway, we use the multi-temporal InSAR (MT-InSAR) technique to extract regional scale subsidence of Wuqing district. Take it into consideration that Wuqing district is a suburban region with large area of low coherence farmland, we select the temporarily coherent point InSAR (TCP-InSAR) approach for MT-InSAR analysis. The TCP-InSAR is a potential approach for detecting land subsidence in low coherence areas as it can identify and analysis coherent points between just two images and can acquire a reliable solution without conventional phase unwrapping. This paper extended the TCP-InSAR with use of ultrashort spatial baseline (USB) interferograms. As thetopographic effects are negligible in the USB interferograms, an external digital elevation model (DEM) is no longer needed in interferometric processing, and the parameters needed to be estimated were simplified at the same time. With use of 17 TerraSAR-X (TSX) images acquired from 2009 to 2010 over Wuqing district, the annual subsidence rates along the high speed railway were derived by the USB-TCPInSAR approach. Two subsidence funnels were found at ShuangJie town and around Wuqing Station with subsidence rate of −17 ∼ −27 mm/year and −7 ∼ −17 mm/year, respectively. The subsidence rates derived by USB-TCPInSAR were compared with those derived by the conventional TCP-InSAR that uses an external DEM for differential interferometry. The mean and the standard deviation of the differences between two types of results at 370697 TCPs are −4.43 × 10−6 mm/year and ±1.4673 mm/year, respectively. Further comparison with the subsidence results mentioned in several other studies were made, which shows good consistencies. The results verify that even without using a DEM the USB-TCPInSAR method can detect land subsidence accurately in flat areas.

Triggered instructions

In this paper, we present triggered instructions , a novel control paradigm for arrays of processing elements (PEs) aimed at exploiting spatial parallelism. Triggered instructions completely eliminate the program counter and allow programs to transition concisely between states without explicit branch instructions. They also allow efficient reactivity to inter-PE communication traffic. The approach provides a unified mechanism to avoid over-serialized execution, essentially achieving the effect of techniques such as dynamic instruction reordering and multithreading, which each require distinct hardware mechanisms in a traditional sequential architecture. Our analysis shows that a triggered-instruction based spatial accelerator can achieve 8X greater area-normalized performance than a traditional general-purpose processor. Further analysis shows that triggered control reduces the number of static and dynamic instructions in the critical paths by 62% and 64% respectively over a program-counter style spatial baseline, resulting in a speedup of 2.0X.

An Improved Persistent Scatterer Interferometry for Subsidence Monitoring in the Tehran Basin

The Southwestern Tehran basin is covered primarily by agricultural fields and is subjected to significant levels of land subsidence phenomena. Conventional SAR interferometry cannot extract deformation information from the available SAR images due to large spatial baselines and temporal de-correlation. Moreover, the proper Persistent Scatterer interferometry method for a rural area (StaMPS, Stanford method for Persistent Scatterer) cannot efficiently operate in areas with high deformation, such as the Tehran basin, because of unwrapping error caused by temporal aliasing of the signal. Therefore, in this work, a method based on StaMPS is developed to address the unwrapping error in the Tehran basin. In the proposed method, the estimated deformation rate from the wrapped phase and the periodogram approach are used to reduce the likelihood of aliasing, and StaMPS is subsequently applied to the residual phase. The method is applied to ENVISAT ASAR images captured between 2003 and 2008, and the mean precision of the estimated deformation is approximately 2.5 mm/yr. A comparison of the results obtained from the proposed method with those from continuous GPS and leveling measurements demonstrates its efficiency.

Measurement of Baseline and Orientation between Distributed Aerospace Platforms

Distributed platforms play an important role in aerospace remote sensing, radar navigation, and wireless communication applications. However, besides the requirement of high accurate time and frequency synchronization for coherent signal processing, the baseline between the transmitting platform and receiving platform and the orientation of platform towards each other during data recording must be measured in real time. In this paper, we propose an improved pulsed duplex microwave ranging approach, which allows determining the spatial baseline and orientation between distributed aerospace platforms by the proposed high-precision time-interval estimation method. This approach is novel in the sense that it cancels the effect of oscillator frequency synchronization errors due to separate oscillators that are used in the platforms. Several performance specifications are also discussed. The effectiveness of the approach is verified by simulation results.

ULTRASHORT-BASELINE PERSISTENT SCATTERER RADAR INTERFEROMETRY FOR SUBSIDENCE DETECTION

Abstract. This paper presents an improved approach of multi-temporal interferometric synthetic aperture radar (InSAR) for detecting land subsidence phenomena by using time series of high resolution SAR images. Our algorithm extends the capability of the temporarily coherent point (TCP) InSAR technique proposed previously to detect subsidence even in the case of a small number of SAR images available for a study area. The approach proposed in this paper is implemented by using the interferograms with ultrashort spatial baselines (USB) through several procedures, including selection of USB interferometric pairs, TCP identification, TCP networking and modeling, as well as TCP solution. As the topographic effects are negligible in the USB interferograms, an external digital elevation model is no longer necessary for differential processing, thus simplifying both TCP modeling and parameter estimating. The algorithm has been tested with the high resolution TerraSAR-X (TSX) images acquired over Tianjin (China), and validated by using the ground-based leveling measurements. The testing results indicate that the density and coverage extent of TCPs can be increased dramatically, and the quality of subsidence measurements derived by the USB-based TCPInSAR can be raised.

Strain and displacement rates during a large earthquake in the South Baikal region

Crustal kinematic characteristics such as strain and displacement rates are important in the monitoring of present-day processes in zones of seismic and industrial hazard. Strain measurements on different temporal and spatial baselines reveal potentially hazardous zones. Data on coseismic displacements and strain can be used to refine earthquake models, and long-term characteristics are important in searching for earthquake precursors and studying the rheology of the crust and fault zones. Tilt measurements in the adit of the Talaya seismic station (51.68° N, 103.64° E, South Baikal region) began in 1985; strain measurements, in 1990; and GPS measurements, in 2000.The data reflect time variation in the local strain parameters and permit a comparison with the GPS data on the region and western Central Asia. The data on strain variations obtained in the Ala-Archa underground observatory (42.63° N, 74.50° E, North Tien Shan) are analyzed together with those obtained in the region by GPS methods.Strain rates on very long baselines were determined using data from permanent IGS stations for Central Asia—the territory expanding from Dzungaria in the south to the Siberian Platform in the north and from the Tien Shan in the west to Lake Baikal in the east. We consider the example of using strain gaging and GPS data to construct a dislocation model and refine the parameters of the Kultuk earthquake (South Baikal region, 27 August 2008, M = 6.3).

Canine left ventricle electromechanical behavior under different pacing modes

Cardiac resynchronization therapy may improve survival and quality of life in patients suffering from heart failure with left ventricular (LV) contraction dyssynchrony. While several studies have investigated electrical or mechanical determinants of synchronous contraction, few have focused on activation contraction coupling at a macroscopic level. The objective of the study was to characterize LV electromechanical behavior and response to pacing in a heart failure model. We analyzed data from 3D electroanatomic non-contact mapping and blood pool SPECT for 12 dogs with right ventricular (RV) tachycardia pacing-induced dilated cardiomyopathy. Surfaces generated by the two modalities were registered. Electrical signals were analyzed, and endocardial wall displacement curves were portrayed. Rapid pacing decreased the mean LV ejection fraction (LVEF) to 20.9 % and prolonged the QRS duration to 79 ± 10 ms (normal range: 40-50 ms). QRS duration remained unchanged with biventricular pacing (88.5 ms), while single site pacing further prolonged the QRS duration (113.3 ms for RV pacing and 111.6 ms for LV pacing). No trend was observed in LV systolic function. Activation duration time was significantly increased with all pacing modes compared to baseline. Finally, electromechanical delay, as defined by the delay between electrical activation and mechanical response, was increased by single site pacing (172.9 ms for RV pacing and 174.6 ms for LV pacing) but not by biventricular pacing (162.4 ms). Combined temporal and spatial coregistration electroanatomic maps and baseline gated blood pool SPECT imaging allowed us to quantify activation duration time, electromechanical delay, and LVEF for different pacing modes. Even if pacing modes did not significantly modify LVEF or activation duration, they produced alterations in electromechanical delay, with biventricular pacing significantly decreasing the electromechanical delay as measured by surface tracings and endocardial non-contact mapping.

An Empirical Assessment of Temporal Decorrelation Using the Uninhabited Aerial Vehicle Synthetic Aperture Radar over Forested Landscapes

We present an empirical assessment of the impact of temporal decorrelation on interferometric coherence measured over a forested landscape. A series of repeat-pass interferometric radar images with a zero spatial baseline were collected with UAVSAR (Uninhabited Aerial Vehicle Synthetic Aperture Radar), a fully polarimetric airborne L-band radar system. The dataset provided temporal separations of 45 minutes, 2, 7 and 9 days. Coincident airborne lidar and weather data were collected. We theoretically demonstrate that UAVSAR measurement accuracy enables accurate quantification of temporal decorrelation. Data analysis revealed precipitation events to be the main driver of temporal decorrelation over the acquisition period. The experiment also shows temporal decorrelation increases with canopy height, and this pattern was found consistent across forest types and polarization.

Protected areas within multifunctional landscapes: Squeezing out intermediate land use intensities in the tropics?

A protected area (PA) tends to be designated in an area where tracts of primary forest remain, often with poor accessibility due to terrain features and yet with some exposure to threats. Typically, a PA is at the start of a ‘forest transition’ gradient. The establishment of a PA influences the whole gradient. We analyzed the temporal patterns of land-use change inside and outside four PAs, with one located in each of Laos, Indonesia, Madagascar and Cameroon. In Laos, in the Viengkham landscape, the rates of conversion of natural forest increased after the designation of the PA and were higher than the spatial baseline predicted. In the three other landscapes, the policies associated with the implementation of PAs increased the conversion rate immediately outside the boundary of the PAs. In Indonesia, in the Bungo landscape, forms of land-use associated with multifunctional agroforestry activities involving rubber trees land-use became the target for conversion to oil palm and monoculture rubber tree crops when the rules on the protection of the remaining natural forest were tightened. We tested a new metric for the degree of integration of forest in multifunctional landscapes which recognizes the surrounding matrix, both as surrogate habitat and as a corridor for tree species. Two important findings were: (i) a ‘leakage’ zone of influence of at least 10km around a PA needs to be included for quantification of the deforestation and degradation changes that may be due to forest protection inside the PA and (ii) agroforest and other mixed tree cover can maintain or increase the degree of integration of forest in the multifunctional landscape for biodiversity maintenance and conservation, while providing a source of livelihood for the local people.

Error Modeling and Analysis for InSAR Spatial Baseline Determination of Satellite Formation Flying

Spatial baseline determination is a key technology for interferometric synthetic aperture radar (InSAR) missions. Based on the intersatellite baseline measurement using dual‐frequency GPS, errors induced by InSAR spatial baseline measurement are studied in detail. The classifications and characters of errors are analyzed, and models for errors are set up. The simulations of single factor and total error sources are selected to evaluate the impacts of errors on spatial baseline measurement. Single factor simulations are used to analyze the impact of the error of a single type, while total error sources simulations are used to analyze the impacts of error sources induced by GPS measurement, baseline transformation, and the entire spatial baseline measurement, respectively. Simulation results show that errors related to GPS measurement are the main error sources for the spatial baseline determination, and carrier phase noise of GPS observation and fixing error of GPS receiver antenna are main factors of errors related to GPS measurement. In addition, according to the error values listed in this paper, 1 mm level InSAR spatial baseline determination should be realized.