Evaluation of insar dem from high-resolution spaceborne sar data

In recent years a new generation of high-resolution SAR satellites became operational like the Canadian Radarsat-2, the Italian Cosmo/Skymed, and the German TerraSAR-X systems. The spatial resolution of such devices achieves the meter domain or even below. Key products derived from remote sensing imagery are Digital Elevation Models (DEM). Based on SAR data various techniques can be applied for such purpose, for example, Radargrammetry (i.e., SAR Stereo) and SAR Interferometry (InSAR). In the framework of the ISPRS Working Group VII/2 "SAR Interferometry" a long term scientific project is conducted that aims at the validation of DEM derived from data of modern SAR satellite sensors. In this paper, we present DEM results yield for the city of Barcelona which were generated by means of SAR Interferometry.DL

Prediction of Forest Stand Attributes Using TerraSAR-X Stereo Imagery

Peer reviewe

Disaster debris estimation using high-resolution polarimetric stereo-SAR

AbstractThis paper addresses the problem of debris estimation which is one of the most important initial challenges in the wake of a disaster like the Great East Japan Earthquake and Tsunami. Reasonable estimates of the debris have to be made available to decision makers as quickly as possible. Current approaches to obtain this information are far from being optimal as they usually rely on manual interpretation of optical imagery. We have developed a novel approach for the estimation of tsunami debris pile heights and volumes for improved emergency response. The method is based on a stereo-synthetic aperture radar (stereo-SAR) approach for very high-resolution polarimetric SAR. An advanced gradient-based optical-flow estimation technique is applied for optimal image coregistration of the low-coherence non-interferometric data resulting from the illumination from opposite directions and in different polarizations. By applying model based decomposition of the coherency matrix, only the odd bounce scattering contributions are used to optimize echo time computation. The method exclusively considers the relative height differences from the top of the piles to their base to achieve a very fine resolution in height estimation. To define the base, a reference point on non-debris-covered ground surface is located adjacent to the debris pile targets by exploiting the polarimetric scattering information. The proposed technique is validated using in situ data of real tsunami debris taken on a temporary debris management site in the tsunami affected area near Sendai city, Japan. The estimated height error is smaller than 0.6m RMSE. The good quality of derived pile heights allows for a voxel-based estimation of debris volumes with a RMSE of 1099m3. Advantages of the proposed method are fast computation time, and robust height and volume estimation of debris piles without the need for pre-event data or auxiliary information like DEM, topographic maps or GCPs

Forest inventory attribute estimation using airborne laser scanning, aerial stereoimagery, radargrammetry and interferometry - Finnish experiences of the 3D techniques

Three-dimensional (3D) remote sensing has enabled detailed mapping of terrain and vegetation heights. Consequently, forest inventory attributes are estimated more and more using point clouds and normalized surface models. In practical applications, mainly airborne laser scanning (ALS) has been used in forest resource mapping. The current status is that ALS-based forest inventories are widespread, and the popularity of ALS has also raised interest toward alternative 3D techniques, including airborne and spaceborne techniques. Point clouds can be generated using photogrammetry, radargrammetry and interferometry. Airborne stereo imagery can be used in deriving photogrammetric point clouds, as very-high-resolution synthetic aperture radar (SAR) data are used in radargrammetry and interferometry. ALS is capable of mapping both the terrain and tree heights in mixed forest conditions, which is an advantage over aerial images or SAR data. However, in many jurisdictions, a detailed ALS-based digital terrain model is already available, and that enables linking photogrammetric or SAR-derived heights to heights above the ground. In other words, in forest conditions, the height of single trees, height of the canopy and/or density of the canopy can be measured and used in estimation of forest inventory attributes. In this paper, first we review experiences of the use of digital stereo imagery and spaceborne SAR in estimation of forest inventory attributes in Finland, and we compare techniques to ALS. In addition, we aim to present new implications based on our experiences

Ricerche di Geomatica 2011

Questo volume raccoglie gli articoli che hanno partecipato al Premio AUTeC 2011. Il premio è stato istituito nel 2005. Viene conferito ogni anno ad una tesi di Dottorato giudicata particolarmente significativa sui temi di pertinenza del SSD ICAR/06 (Topografia e Cartografia) nei diversi Dottorati attivi in Italia

Metsien kartoitus ja seuranta aktiivisella 3D-kaukokartoituksella

The main aim in forest mapping and monitoring is to produce accurate information for forest managers with the use of efficient methodologies. For example, it is important to locate harvesting sites and stands where forest operations should be carried out as well as to provide updates regarding forest growth, among other changes in forest structure. In recent years, remote sensing (RS) has taken a significant technological leap forward. It has become possible to acquire three-dimensional (3D), spatially accurate information from forest resources using active RS methods. In practical applications, mainly 3D information produced by airborne laser scanning (ALS) has opened up groundbreaking potential in natural resource mapping and monitoring. In addition to ALS, new satellite radars are also capable of acquiring spatially accurate 3D information. The main objectives of the present study were to develop 3D RS methodologies for large-area forest mapping and monitoring applications. In substudy I, we aim to map harvesting sites, while in substudy II, we monitor changes in the forest canopy structure. In studies III-V, efficient mapping and monitoring applications were developed and tested. In substudy I, we predicted plot-level thinning maturity within the next 10-year planning period. Stands requiring immediate thinning were located with an overall accuracy of 83%-86% depending on the prediction method applied. The respective prediction accuracy for stands reaching thinning maturity within the next 10 years was 70%-79%. Substudy II addressed natural disturbance monitoring that could be linked to forest management planning when an ALS time series is available. The accuracy of the damaged canopy cover area estimate varied between -16.4% to 5.4%. Substudy II showed that changes in the forest canopy structure can be monitored with a rather straightforward method by contrasting bi-temporal canopy height models. In substudy III, we developed a RS-based forest inventory method where single-tree RS is used to acquire modelling data needed in area-based predictions. The method uses ALS data and is capable of producing accurate stand variable estimates even at the sub-compartment level. The developed method could be applied in areas with sparse road networks or when the costs of fieldwork must be minimized. The method is especially suitable for large-area biomass or stem volume mapping. Based on substudy IV, the use of stereo synthetic aperture radar (SAR) satellite data in the prediction of plot-level forest variables appears to be promising for large-area applications. In the best case, the plot-level stem volume (VOL) was predicted with a relative error (RMSE%) of 34.9%. Typically, such a high level of prediction accuracy cannot be obtained using spaceborne RS data. Then, in substudy V, we compared the aboveground biomass and VOL estimates derived by radargrammetry to the ALS estimates. The difference between the estimation accuracy of ALS based and TerraSAR X based features was smaller than in any previous study in which ALS and different kinds of SAR materials have been compared. In this thesis, forest mapping and monitoring applications using active 3D RS were developed. Spatially accurate 3D RS enables the mapping of harvesting sites, the monitoring of changes in the canopy structure and even the making of a fully RS-based forest inventory. ALS is carried out at relatively low altitudes, which makes it relatively expensive per area unit, and other RS materials are still needed. Spaceborne stereo radargrammetry proved to be a promising technique to acquire additional 3D RS data efficiently as long as an accurate digital terrain model is available as a ground-surface reference.Metsien kartoitus ja seuranta aktiivisella 3D-kaukokartoituksella. Metsävaroista kerätään mahdollisimman tarkkaa tietoa metsänomistajan päätöksenteon tueksi. Tietoa kerätään puustotunnusten lisäksi toimenpidekohteista ja metsässä tapahtuvista muutoksista, kuten kasvusta ja luonnontuhoista. Laajojen metsäalueiden kartoituksessa käytetään apuna lentokoneesta tai satelliiteista tehtävää kaukokartoitusta. Metsien kaukokartoitus on viime vuosina ottanut merkittävän kehitysaskeleen, kun aktiiviset 3D-kaukokartoitusmenetelmät ovat yleistyneet. Aktiivisessa kaukokartoituksessa, kuten laserkeilauksessa ja tutkakuvauksessa instrumentti vastaanottaa lähettämäänsä säteilyä. Laserkeilaus tuottaa kohteesta 3D-havaintoja, jotka metsäalueilla kuvaavat suoraan puuston pituutta ja metsän tiheyttä. Laserkeilauksella kohteesta saadaan tällä hetkellä tyypillisesti 0,5−20 havaintoa/m2. Laserkeilaus tehdään lentokoneesta 500−3000 m korkeudesta, jolloin aineiston hankinta laajoilta alueilta on kallista verrattuna satelliittikuviin. Myös satelliittitutkakuvilta voidaan tuottaa spatiaalisesti tarkkaa 3D-tietoa, jonka pistetiheys on tosin huomattavasti harvempaa kuin laserkeilauksella. Tutkimuksessa kehitettiin sovelluksia metsien kartoitukseen ja seurantaan hyödyntäen aktiivisia 3D-kaukokartoitusmenetelmiä. Metsiköiden toimenpidetarvetta ennustettiin onnistuneesti laserkeilausaineiston avulla. Harvennettaviksi luokitellut metsiköt pystyttiin kartoittamaan 70%−86% tarkkuudella. Kahden ajankohdan laserkeilausaineistoja käytettiin lumituhojen vuoksi vaurioituneiden puiden kartoittamiseen. Tuhoutuneen latvuspinta-alan kartoitus perustui laserkeilausaineistosta tuotettujen latvusmallien erotuskuviin. Kehitetty menetelmä soveltuu latvusrakenteessa tapahtuneiden muutosten, kuten lumi- ja tuulituhojen, kartoittamiseen ja seurantaan. Laajojen metsäalueiden kartoitus perustuu yleensä kaksivaiheeseen inventointimenetelmään, jossa käytetään maastomittauksia ja tiedon yleistyksessä kaukokartoitusaineistoa. Kartoitusta voidaan tehostaa joko maastomittauksia vähentämällä tai hyödyntämällä mahdollisimman halpaa kaukokartoitusaineistoa. Tutkimuksessa kehitettiin täysin kaukokartoitukseen perustuva kaksivaiheinen metsien inventointimenetelmä. Tarvittava maastotieto mitattiin suoraan laserkeilausaineistosta. Menetelmä soveltuu puuston tilavuuden tai biomassan kartoitukseen erityisesti alueille, joilla maastomittausten kustannukset ovat merkittävät. Satelliittitutkakuvat ovat potentiaalinen aineisto etenkin laajojen alueiden metsävarojen seurannassa. Synteettisen apertuurin tutka (SAR)-stereokuvilta mitattiin automaattisesti 3D-pisteitä, joita käytettiin puustotunnusten ennustamisessa. Keskitilavuus ennustettiin parhaimmillaan lähes samalla tarkkuudella kuin laserkeilauksella. Tutkimus osoitti aktiivisen 3D-kaukokartoitustiedon mahdollistavan entistä yksityiskohtaisemman metsien kartoituksen ja seurannan

Utilisation de la stéréo radargrammétrie RADARSAT-2 pour le suivi de la fonte des calottes glaciaires Barnes et Penny (Île de Baffin, Nunavut, Canada)

Résumé : Le contexte récent d’accélération de la fonte des glaciers et calottes glaciaires (GCG) de l’archipel arctique canadien, jumelé aux difficultés de suivi des GCG de cette région, rendent essentiels le développement et l’utilisation de nouvelles approches innovatrices de suivi. Le potentiel de la stéréo radargrammétrie (SRG) RADARSAT-2 est ici caractérisé pour l’extraction d’élévations et le calcul de changements d’élévation et de bilans de masse (historiques et récents) sur les calottes glaciaires Barnes et Penny (Nunavut, Canada). Par la méthode semi-automatisée de recherche de corrélation à partir de couples stéréoscopiques RADARSAT-2 de 2013 (mode wide ultra-fin; résolution spatiale de 3 m; taille d’image de 50 km x 50 km), une précision verticale de ~7 m (LE68) est mesurée sur la terre ferme, et cette valeur de précision est possiblement légèrement supérieure sur la calotte Barnes, étant donné la variabilité de profondeur de pénétration. Par captage 3D, une précision altimétrique de ~3-4 m (LE68) est mesurée par différents photo-interprètes à partir de couples RADARSAT de 2012 en zone d’ablation de la calotte Penny. Sur la calotte Barnes, les changements d’élévation mesurés par rapport aux premiers modèles numériques de terrain disponibles permettent de mesurer un bilan de masse spécifique historique (1960-2013) de -0,49 ± 0,20 m w.e./année, pour un bilan de masse total de -2,9 Gt/année. Entre 2005 et 2013, le bilan de masse spécifique de cette calotte augmente significativement à -1,20 ± 0,86 m w.e./année, pour un bilan de masse total de -7 Gt/année. En zone d’ablation de la calotte Penny, un changement d’élévation annuel moyen de -0,59 m/année est mesuré entre 1958 et 2012. Parallèlement, plusieurs aspects méthodologiques et techniques sont discutés et analysés. Des profondeurs de pénétration nulles (bande C) sont mesurées à partir des images acquises sur la calotte Barnes à la toute fin de la saison d’ablation (fin septembre/début octobre), alors que cette profondeur augmente à ~2,5-3 m pour des images acquises à la fin octobre/début novembre (période de gel). Nos résultats suggèrent aussi que le modèle de fonction rationnelle, lorsqu’utilisé avec des images RADARSAT-2 en mode wide ultra-fin, permet d’obtenir des précisions plus constantes que le modèle hybride de Toutin. De par son indépendance des conditions météorologiques, son utilisation possible sans point de contrôle et sa simplicité de traitement, la SRG RADARSAT-2 s’avère donc être une excellente alternative aux technologies actuelles pour le suivi de GCG situés dans des régions affectées par des contraintes opérationnelles importantes.Abstract : Given the recent melt acceleration of the Canadian arctic archipelago’s ice caps and the monitoring difficulties of this remote region, the development of new innovative monitoring tools has become essential. Here, the potential of the RADARSAT-2 stereo radargrammetry (SRG) is characterized for elevations extraction, as well as for elevation changes/mass balances calculations (historical and recent) on Barnes and Penny ice caps (Nunavut, Canada). Using the semi-automatic approach of correlation search from RADARSAT-2 stereoscopic couples of 2013 (wide ultra-fine mode; spatial resolution of 3 m; coverage of 50 km x 50 km), a vertical precision of ~7 m (LE68) is measured on ice-free terrain and this precision is possibly slighty worse on the ice cap because of the penetration depth’s variability. On the other hand, the 3D vision extraction approach reveals an altimetric precision of ~3-4 m (LE68) on the ablation area of the Penny Ice Cap. On the Barnes Ice Cap, elevation changes calculated relative to the oldest digital elevation models available allows to calculate an historical specific mass balance (1960-2013) of -0,49 ± 0,20 m w.e./year, resulting in a total annual mass balance of -2,9 Gt/year. Between 2005 and 2013, the specific mass balance of this ice cap increases to -1,20 ± 0,86 m w.e./year, which equals to a total annual mass balance f -7 Gt/year. On Penny Ice Cap’s ablation area, an average elevation change of -0,59 m/year is measured between 1958 and 2012. As also suggested in the literature, the recent melt acceleration is highly linked to warmer summer temperatures. Methodological and technical aspects are also presented and analyzed. No penetration depth (C band) is perceived on elevations derived from late ablation season images (late September/beginning of October), while a penetration of ~2,5-3 m is measured from images acquired in late October/beginning of November (freeze period). Our results also suggest the superiority and better consistency of the rational function model for geometrical correction of wide ultra-fine mode RADARSAT-2 images, compared to the hybrid Toutin’s model. Because of its all-weather functionality, its possible use without any ground control point and the simplicity and facility of its treatment, the RADARSAT-2 SRG represents a really good technology for glacier monitoring in regions affected by serious operational constraints