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A three dimensional scatterer map extends the DEM information in urban areas / Nico Adam in Revue Française de Photogrammétrie et de Télédétection, n° 182 (Juin 2006)  

Public [article]  inRevue Française de Photogrammétrie et de Télédétection > n° 182 (Juin 2006) . - pp 5 - 9 Titre : A three dimensional scatterer map extends the DEM information in urban areas Type de document : Article/Communication Auteurs : Nico Adam, Auteur ; M. Eineder, Auteur Année de publication : 2006 Conférence : ISPRS 2006, Commission 1 Symposium, From sensors to imagery 03/07/2006 06/07/2006 Champs-sur-Marne [Paris Marne-la-Vallée] France OA ISPRS Archives Article en page(s) : pp 5 - 9 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image radar et applications [Termes IGN] coin réflecteur [Termes IGN] données polarimétriques [Termes IGN] image radar moirée [Termes IGN] image SRTM [Termes IGN] interféromètrie par radar à antenne synthétique [Termes IGN] MNS SRTM [Termes IGN] modèle 3D de l'espace urbain [Termes IGN] modèle numérique de surface [Termes IGN] Munich [Termes IGN] précision millimétrique [Termes IGN] tomographie [Termes IGN] zone urbaine Résumé : (Auteur) The generation of digital elevation models (DEMs) by space-born InSAR is a well-established remote sensing technique. Several application projects as for instance the shuttle radar topography mission (SRTM) have proven the outstanding capability to map the Earth's surface globally with great accuracy and constant resolution applying this technique. The short mission time of only eleven days guaranteed the homogenous quality of the generated DEM. The typical InSAR-DEM provides a snapshot of the terrain elevation at the time of acquisition including the vegetation cover. A limitation is that the Earth's cover is mapped only down to a mean radar penetration depth. Polarimetry can be applied to separate volume scattering from the double bounce effect on the ground in forested areas. But in urban areas this scattering model can not be applied. This is in contrast to the great interest in urban areas caused by the high population density and change. Nowadays, the permanent scatterer interferometry which has been invented at POLIMI is working operational and can provide supplementing information. It allows a monitoring of urban areas over time spans of more than ten years. E.g. the subsidence in such spots can be detected and monitored with millimetre accuracy. The separation of the orbit, atmosphere and topography phase effects form the basis for the extreme accuracy regarding the displacement measurement. Furthermore, the PS estimation results in a high precision DEM update at the PS position. The structure of the cities and the radar observation geometry are the reason that this simple elevation concept needs to be extended. It is very likely that more than one dominant scatterer is inside a resolution cell. Tomography can resolve this ambiguity and provides the reflectivity along cross slant range height. Consequently, a real but irregular sampled 3D map of the persistent radar scatterers can be generated which describes the city better. The dominant radar scatterers are related to buildings and other men made features. This is the reason the exact three-dimensional locations of the scatterers provide a lot of useful information on the area and the shape of the city and allowing various applications. Such a 3D map can be a better DEM input for each PS processing that allows an effective PS detection and optimal parameter estimation. A new parametric method for the detection and relative estimation of the two dominant scatterers configuration inside of a resolution cell has been developed. The developed method is more robust because it uses amplitude data only and complements the full tomography which includes the phase information. The city of Munich is one of DLR's testsite for the PS processing and the developed tomography algorithms. Examples for the generated data set and applications will be shown. The permanent scatterers are assessed in situ and the 3D position of the scatterers is checked and compared to the estimates. Copyright SFPT Numéro de notice : A2006-617 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : sans En ligne : https://www.isprs.org/proceedings/XXXVI/part1/Papers/T09-40.pdf Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28340 [article]

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Calibration of the optech ALTM-3100 laser scanner intensity data using brightness targets / E. Ahokas in Revue Française de Photogrammétrie et de Télédétection, n° 182 (Juin 2006)  

Public [article]  inRevue Française de Photogrammétrie et de Télédétection > n° 182 (Juin 2006) . - pp 10 - 16 Titre : Calibration of the optech ALTM-3100 laser scanner intensity data using brightness targets Type de document : Article/Communication Auteurs : E. Ahokas, Auteur ; S. Kaasalainen, Auteur ; et al., Auteur Année de publication : 2006 Conférence : ISPRS 2006, Commission 1 Symposium, From sensors to imagery 03/07/2006 06/07/2006 Champs-sur-Marne [Paris Marne-la-Vallée] France OA ISPRS Archives Article en page(s) : pp 10 - 16 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Acquisition d'image(s) et de donnée(s) [Termes IGN] ALTM [Termes IGN] angle d'incidence [Termes IGN] angle de visée [Termes IGN] caméra numérique [Termes IGN] correction atmosphérique [Termes IGN] étalonnage en vol [Termes IGN] étalonnage géométrique [Termes IGN] étalonnage radiométrique [Termes IGN] Lidar [Termes IGN] point d'appui [Termes IGN] rapport signal sur bruit [Termes IGN] test de performance Résumé : (Auteur) In this paper the calibration of Optech ALTM 3100 laser scanner intensity is reported using airborne experiments and known brightness targets. The Finnish Geodetic Institute has had a permanent photogrammetric test field in Sjokulla Kirkkonummi since 1994. This test field contains permanent and transportable test targets for radiometric calibration, permanent ground control points for small, medium and large-scale geometric calibration and also test bar targets for spatial analysis of analogue and digital aerial cameras. Since 2000 LiDAR testing has also been carried out, the latest being Optech ALTM 3100 campaign in 12-14 July 2005. Eight portable brightness targets with nominal reflectance of 5 %, 10 %, 20 %, 25 %, 30 %, 45 %, 50 % and 70 % were in use for LiDAR testing. Flying heights were about 200, 1000 and 3000 m above ground level. Intensity values need to be corrected with respect to range, incidence angle (both BRDF and range correction), atmospheric transmittance, attenuation using dark object addition and transmitted power (because difference in PRF will lead to different transmitter power values). After these corrections, the intensity values were directly relative to target reflectance. Flight heights of 200 m and 1000 m are suitable for intensity calibration using artificial test targets due to the practical aspects of the calibration (size of the calibrator). With the 3000 m altitude signals with reflectance of less or equal of 10% could not be recorded most probably due to insufficient signal-to-noise ratio. Thus, the test target reflectance should exceed 10% to give a reliable distance measurement from 3000 m altitude. Numéro de notice : A2006-618 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : sans En ligne : https://www.isprs.org/proceedings/XXXVI/part1/Papers/T03-11.pdf Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28341 [article]

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Classification of fully polarimetric SAR data for land use cartography / Cédric Lardeux in Revue Française de Photogrammétrie et de Télédétection, n° 182 (Juin 2006)    

Public [article]  contenu dans ISPRS Commission 1 Symposium 2006, Paris, Marne-la-Vallée, 3-6 Juillet 2006: Des capteurs à l'imagerie, vol 1. Proceedings / Alain Baudoin (2006)   inRevue Française de Photogrammétrie et de Télédétection > n° 182 (Juin 2006) . - pp 23 - 27 Titre : Classification of fully polarimetric SAR data for land use cartography Type de document : Article/Communication Auteurs : Cédric Lardeux, Auteur ; Pierre-Louis Frison , Auteur ; Jean-Paul Rudant , Auteur ; et al., Auteur Année de publication : 2006 Conférence : ISPRS 2006, Commission 1 Symposium, From sensors to imagery 03/07/2006 06/07/2006 Champs-sur-Marne [Paris Marne-la-Vallée] France OA ISPRS Archives Article en page(s) : pp 23 - 27 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image radar et applications [Termes IGN] bande L [Termes IGN] bande P [Termes IGN] carte d'occupation du sol [Termes IGN] classification par séparateurs à vaste marge [Termes IGN] données polarimétriques [Termes IGN] image AIRSAR [Termes IGN] polarimétrie radar [Termes IGN] Polynésie française Résumé : (Auteur) French Polynesia islands are located at the middle of the South Pacific Ocean. They are thus subject to a strong environmental planning leading to landscape changes as well as to the introduction of invasive species. This study comes within the framework of the global cartography and inventory of the Polynesian landscape. An AIRSAR airborne mission took place in August 2000 over the main Polynesian islands. Polarimetric SAR data are particularly adapted to the cloudy conditions generally encountered over the South Pacific Islands. Fully polarimetric data allows the analysis of a geometrical and physical point of view. Different decompositions, such as H/A/a or based on the Pauli formalism have shown their potential for such applications. In order to apply these indicators and to produce a semi-automatic cartography of the Tubuai Island, we choose to use the SVM (Support Vector Machine) as supervised classifier. These results are also compared with the Wishart classifier based on the analysis of the polarimetric coherency matrix only. As our full polarimetric data are also available in P and L bands, this study evaluates the contribution of the different wavelength. This study shown that the combination of SVM and full polarimetric data, associates with different wavelength, gives promising results. Copyright SFPT Numéro de notice : A2006-619 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueNat DOI : sans En ligne : https://www.isprs.org/proceedings/XXXVI/part1/Papers/T09-39.pdf Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28342 [article]

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en open access Classification of fully polarimetric... - pdf editeur ISPRS Adobe Acrobat PDF

Assessment and comparison of registration algorithms between aerial images and laser point clouds / A. Pothou in Revue Française de Photogrammétrie et de Télédétection, n° 182 (Juin 2006)  

Public [article]  inRevue Française de Photogrammétrie et de Télédétection > n° 182 (Juin 2006) . - pp 28 - 31 Titre : Assessment and comparison of registration algorithms between aerial images and laser point clouds Type de document : Article/Communication Auteurs : A. Pothou, Auteur ; S. Karamitos, Auteur ; et al., Auteur Année de publication : 2006 Conférence : ISPRS 2006, Commission 1 Symposium, From sensors to imagery 03/07/2006 06/07/2006 Champs-sur-Marne [Paris Marne-la-Vallée] France OA ISPRS Archives Article en page(s) : pp 28 - 31 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications photogrammétriques [Termes IGN] analyse comparative [Termes IGN] couple stéréoscopique [Termes IGN] données lidar [Termes IGN] données localisées 3D [Termes IGN] fusion de données multisource [Termes IGN] image aérienne [Termes IGN] semis de points [Termes IGN] superposition d'images Résumé : (Auteur) Photogrammetry, has been providing accurate coordinate measurements through the stereoscopic method for many years. LiDAR on the other hand, is becoming the prime method for large-scale acquisition of elevation data due to its capability of directly measuring 3D coordinates of a huge number of points. LiDAR can provide measurements in areas where traditional photogrammetric techniques encounter problems mainly due to occlusions or shadows. However LiDAR has also its limitations due to its inability of thematic information recording. The aim of this research is the optimum exploitation of both these elevation data sources. Usually this process is referred to as fusion of two datasets and exploits the advantages of both sources. The prerequisite step for the fusion of the two datasets is the co-registration. This paper describes a co-registration procedure, between the two datasets, that takes place through a 3D transformation. The performance of the algorithm A, which was presented in an earlier publication by the authors, and also an extended algorithm B based on the inclusion of the 7 transformation parameters, during the whole registration procedure, have been presented. Both algorithms developed based on the minimization of the distances between points of one surface to surface patches of the other surface, parallel to the corresponding surface normals. A comparison has also been performed between the results of the algorithms developed, in order to assess the geometric stability of the transformations, the analysis of the results, the effects on the registration and the accuracy of the derived parameters through stand-alone macros. Due to improved geometry of extended algorithm B an increased performance was expected. In fact the algorithm B converges 50% faster than the algorithm A. To support these tests a block of aerial images and a one month apart 3D laser point cloud were collected. Copyright SFPT Numéro de notice : A2006-620 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueNat DOI : sans En ligne : https://www.isprs.org/proceedings/XXXVI/part1/Papers/PS2-24.pdf Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28343 [article]

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Matching topographic surfaces : application to lidar and photogrammetric surfaces / Frédéric Bretar in Revue Française de Photogrammétrie et de Télédétection, n° 182 (Juin 2006)  

Public [article]  contenu dans ISPRS Commission 1 Symposium 2006, Paris, Marne-la-Vallée, 3-6 Juillet 2006: Des capteurs à l'imagerie, 2. Tome 2 / Alain Baudoin (2006)   inRevue Française de Photogrammétrie et de Télédétection > n° 182 (Juin 2006) . - pp 41 - 46 Titre : Matching topographic surfaces : application to lidar and photogrammetric surfaces Type de document : Article/Communication Auteurs : Frédéric Bretar, Auteur ; Michel Roux, Auteur ; Marc Pierrot-Deseilligny , Auteur Année de publication : 2006 Conférence : ISPRS 2006, Commission 1 Symposium, From sensors to imagery 03/07/2006 06/07/2006 Champs-sur-Marne [Paris Marne-la-Vallée] France OA ISPRS Archives Article en page(s) : pp 41 - 46 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications photogrammétriques [Termes IGN] appariement d'images [Termes IGN] approximation [Termes IGN] données lidar [Termes IGN] données localisées 3D [Termes IGN] image optique [Termes IGN] modèle numérique de surface [Termes IGN] points homologues [Termes IGN] semis de points [Termes IGN] superposition d'images [Termes IGN] transformation géométrique Résumé : (Auteur) If photogrammetry has been used for a long time to describe the topography, airborne laser systems are nowadays well-known to provide an accurate representation of terrestrial landscapes through irregular 3D point clouds. Both technologies have their pros and cons that a joint use may optimize to reach a better description of 3D scenes. Beyond the adjustment problem of laser strips, combining optical and laser data is at first a registration problem, especially when using high resolution images. We propose in this paper a methodology for registering laser strips with regard to a photogrammetric derived Digital Surface Model (DSM) which has been computed from a set of known pose calibrated images. Based on the main hypothesis that the geometrical frames of laser systems and digital cameras are linked with a regular function, we describe an algorithm based on the calculation of linear approximations of this transform with 3D local translations. Due to the irregular spatial distribution of laser data and the difficulty of detecting homologous points in the DSM, we adopt a statistical strategy to find patch correspondences which leads to analyze the distribution of a certain vector set of potential homologous candidates. We then propose to estimate an analytical model through a weighted sliding window strategy. Laser strips are corrected globally in a chronological order. The algorithm is validated onto synthetic transforms. Experimental results show the capability of the registration algorithm on raw laser data sets. Copyright SFPT Numéro de notice : A2006-621 Affiliation des auteurs : MATIS (1993-2011) Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueNat DOI : sans En ligne : https://www.isprs.org/proceedings/XXXVI/part1/Papers/PS2-25.pdf Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28344 [article]

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Evaluation of the potential of SAR ERS and ASAR Envisat sensors in multi-incidence and multi-polarisation modes for landscape study in French Guyana: examples of Kourou and Saint Laurent du Maroni / J.L. Kouame in Revue Française de Photogrammétrie et de Télédétection, n° 182 (Juin 2006)    

Public [article]  contenu dans ISPRS Commission 1 Symposium 2006, Paris, Marne-la-Vallée, 3-6 Juillet 2006: Des capteurs à l'imagerie, 2. Tome 2 / Alain Baudoin (2006)   inRevue Française de Photogrammétrie et de Télédétection > n° 182 (Juin 2006) . - pp 53 - 53 Titre : Evaluation of the potential of SAR ERS and ASAR Envisat sensors in multi-incidence and multi-polarisation modes for landscape study in French Guyana: examples of Kourou and Saint Laurent du Maroni Type de document : Article/Communication Auteurs : J.L. Kouame, Auteur ; Pierre-Louis Frison , Auteur ; et al., Auteur Année de publication : 2006 Article en page(s) : pp 53 - 53 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image radar et applications [Termes IGN] analyse comparative [Termes IGN] analyse discriminante [Termes IGN] angle d'incidence [Termes IGN] coefficient de rétrodiffusion [Termes IGN] image Envisat-ASAR [Termes IGN] image ERS-SAR [Termes IGN] image radar [Termes IGN] Kourou [Termes IGN] mesure de la qualité [Termes IGN] occupation du sol [Termes IGN] polarisation [Termes IGN] Saint-Laurent-du-Maroni [Termes IGN] surveillance du littoral [Termes IGN] variation saisonnière Résumé : (Auteur) This study aims to assess the contribution of ENVISAT ASAR data for the monitoring of the littoral plains of Kourou and Saint Laurent du Maroni (French Guyana). It presents results of qualitative and quantitative analyses of SAR ERS and ASAR ENVISAT data based on the following comparative criteria for landscape types discrimination: 1- Comparison between SAR ERS and ASAR ENVISAT in same configuration acquisition (mode IS2), 2- Seasonal influences (dry vs rainy season effects), 3- Incidence angle influences (exploitation of ASAR ENVISAT incidence angle range), 4- Polarization influences (exploitation of ASAR ENVISAT Image and Alternating Polarization modes data). The calibration of the different considered radar images allows their inter comparison in order to obtain information about landscape type's properties (dielectric, moistures, real evolutions) and on homogeneous parcel of land. The study showed that different parameters, like the season, the incidence angle, and the polarization, strongly influence the radar signal observed over such landscape types. In addition, results show that ASAR-IS2 mode, similar to ERS-SAR configuration ensures the continuity of SAR ERS-1&2 for land surface monitoring. However, it arises that discrimination between various types of landscape are confusing when analysing the backscattering coefficient values alone. The backscattering coefficients only cannot allow discriminating all the different landscape classes. Other parameters like texture, structure, geographical position, form and size are needed for landscape type's discrimination from radar images. Copyright SFPT Numéro de notice : A2006-622 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueNat DOI : sans En ligne : https://www.isprs.org/proceedings/XXXVI/part1/Papers/PS2-27.pdf Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28345 [article]

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en open access Evaluation of the potential of SAR ERS... - pdf editeur ISPRS Adobe Acrobat PDF

Performance analysis of ALTM 3100EA: instrument specifications and accuracy of Lidar data / R.V. Ussyshkin in Revue Française de Photogrammétrie et de Télédétection, n° 182 (Juin 2006)  

Public [article]  inRevue Française de Photogrammétrie et de Télédétection > n° 182 (Juin 2006) . - pp 66 - 72 Titre : Performance analysis of ALTM 3100EA: instrument specifications and accuracy of Lidar data Type de document : Article/Communication Auteurs : R.V. Ussyshkin, Auteur ; B. Smith, Auteur Année de publication : 2006 Conférence : ISPRS 2006, Commission 1 Symposium, From sensors to imagery 03/07/2006 06/07/2006 Champs-sur-Marne [Paris Marne-la-Vallée] France OA ISPRS Archives Article en page(s) : pp 66 - 72 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Acquisition d'image(s) et de donnée(s) [Termes IGN] ALTM [Termes IGN] capteur aérien [Termes IGN] données lidar [Termes IGN] instrumentation Optech [Termes IGN] précision des données [Termes IGN] précision des mesures [Termes IGN] spécification de produit [Termes IGN] test de performance Résumé : (Auteur) Over the last decade the number of airborne lidar systems currently deployed and operating in the field has grown impressively. This growth has intensified the level of competition among lidar equipment manufacturers. As manufacturers vie for increased market share with claims of ever higher accuracy specifications, lidar end users wonder how these specifications actually affect achievable accuracy of the lidar data. Aware of the interest that professional organizations such as ISPRS/ASPRS have shown in establishing quality control guidelines for reporting accuracy in lidar data, Optech Incorporated, a leading manufacturer of airborne lidar equipment, conducted a series of studies that examined issues that included, among others, vertical accuracy and Position and Orientation System (POS) performance. Since accuracy specifications can be the product of different testing methodologies and subject to the interpretation of data, the final arbiter of competing claims is actual system performance. The studies that Optech carried out included performance analyses of the ALTM 31OOEA laser mapping system. This instrument demonstrated that it is capable of producing mapping data with relative accuracies on the sub-decimeter level. However, the limiting factors in obtaining overall absolute sub-decimeter accuracies are often due to the performance of various subsystems that contribute to the total ALTM error budget. This paper represents the manufacturer's effort to relate the engineering analysis of instrument performance to what is demonstrably achievable accuracy in the lidar data of end users. Copyright SFPT Numéro de notice : A2006-623 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueNat DOI : sans En ligne : https://www.isprs.org/proceedings/XXXVI/part1/Papers/PS2-28.pdf Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28346 [article]

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Co-registration and inter-sensor comparison of MODIS and LANDSAT 7 ETM+ data aimed at NDVI calculation / P. Boccardo in Revue Française de Photogrammétrie et de Télédétection, n° 182 (Juin 2006)  

Public [article]  inRevue Française de Photogrammétrie et de Télédétection > n° 182 (Juin 2006) . - pp 74 - 79 Titre : Co-registration and inter-sensor comparison of MODIS and LANDSAT 7 ETM+ data aimed at NDVI calculation Type de document : Article/Communication Auteurs : P. Boccardo, Auteur ; Enrico Borgogno Mondino, Auteur ; et al., Auteur Année de publication : 2006 Conférence : ISPRS 2006, Commission 1 Symposium, From sensors to imagery 03/07/2006 06/07/2006 Champs-sur-Marne [Paris Marne-la-Vallée] France OA ISPRS Archives Article en page(s) : pp 74 - 79 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique [Termes IGN] analyse comparative [Termes IGN] erreur systématique [Termes IGN] homologie [Termes IGN] image Landsat-ETM+ [Termes IGN] image Terra-MODIS [Termes IGN] limite de résolution géométrique [Termes IGN] Normalized Difference Vegetation Index [Termes IGN] superposition d'images Résumé : (Auteur) To evaluate accuracy of low resolution vegetation mapping for hydrological purposes, a comparative study of NDVI images derived from MODIS and Landsat 7 ETM+ data has been done. Main goal is to understand how effective MODIS images can be for vegetation characterization on large areas, as compared to the Landsat 7 ETM+ ones. In this paper a methodology is proposed with the aim of measuring the difference between NDVI values derived from the two different data, considering synthetic parameters and investigating their dependency on the geometric resolution of the images. Great attention was paid to the problem of the geometric co-registration of the two types of data. This is a very sensitive parameter for the subsequent analysis. A mixed approach was adopted: images were firstly orthoprojected to eliminate sensor geometry and relief displacement effects; subsequently, a refining image-to-image co-registration procedure was carried out through a homographic transformation implemented in a self-developed routine. Two pairs of contemporary images (MODIS and Landsat 7) were used as benchmarks for our tests. Simplified procedures aimed at calibrating images and at removing atmospheric noise were performed. The resulting corrected images were used to calculate NDVI images. These ones (two pairs) were then compared through a statistical approach in order to investigate how a different geometric resolution can influence the NDVI values. The proposed approach is not a traditional image based (matrix comparison) but a new one. NDVI value correspondences were considered between the MODIS pixel and the group of Landsat pixels belonging to the polygon which represents the considered MODIS pixel in the Landsat image space. Statistics extracted on-the-fly from these Landsat pixels were used to investigate in depth the relationship between them and NDVI value of the corresponding MODIS pixel. NDVI differences were calculated between the single NDVI MODIS values and a synthetic parameter (mean value) of the homologous Landsat pixel group. A direct comparison between the NDVI values obtained from MODIS and Landsat 7 images has shown a systematic error that can be read as bias (MODIS NDVI over estimation). This led the authors to determine a suitable model in order to eliminate the bias, whose presence would have conditioned later comparisons. Original MODIS image was then corrected through the defined model. This has been designed to be suitable for any MODIS image acquired over the same area (parameterization was used). New NDVI differences were calculated using the corrected MODIS images and the previous Landsat 7 ones. In order to investigate the nature of the residual differences and to try to recognize the critical MODIS pixels, some considerations were made concerning the statistics of each corresponding group of Landsat pixels. A classification of the MODIS pixel was generated according to the behaviour of their differences with respect to the adopted statistics. Copyright SFPT Numéro de notice : A2006-624 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueNat DOI : sans En ligne : https://www.isprs.org/proceedings/XXXVI/part1/Papers/PS1-04.pdf Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28347 [article]

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