La Surveillance du Dioxyde d'Azote a Madrid au Moyen d'Echantillonneurs Passifs. Evaluation Critique de la Conception du Reseau

Abstract not availableNA-NOT AVAILABL

Plane-based Calibration of a Camera with Varying Focal Length: the Centre Line Constraint

This paper deals with the problem of calibrating a (moving) camera with varying focal length, from views of a planar pattern with a known Euclidean structure. The main issue under discussion is to find a new method whose complexity does not dramatically increase with the number of views, contrary to existing methods. Our contribution is to relate this calibration problem to the Centre Line (CL) constraint, that is the principal point locus when planar figures are in perpective correspondence, in accordance with Poncelet's theorem. We demonstrate that the CL equation is irrespective of the focal length and holds for each view, with only three unknown parameters whose values are constant in the images. We define its analytic equation with coefficients computed from the world-plane to image homography matrices. An important aspect is that we can make use of it as a linear cost function that expresses a geometric error (instead of algebraic errors in existing methods). We explain why an "optimal" solutioncan be obtained when pixels are rectangular. The simulations on synthetic data and an application with real images confirm the two strong points of our method with respect to existing ones: a lower computation cost and a better system conditioning that permits to obtain more accurate results.

Le esperienze e gli indirizzi della Comunita' Europea nella armonizzazione dei metodi di misura per il controllo della qualita' dell'aria

WE PRESENT THE ACTIONS UNDERTAKEN BY THE EC COMMISSION FOR THE MAINTENANCE OF AIR QUALITY STANDARDS DEFINED IN THE EC DIRECTIVES.NA-NOT AVAILABL

Le Programme Europeen d'Harmonisation sur la Revision de Methode de Reference pour la Mesure des Poussieres, la Conceptions des Reseaux de Surveillance, et Orientations

Abstract not availableNA-NOT AVAILABL

The Role of the European Commission in the Maintenance of Air Quality Standards

WE DESCRIBE INTERCOMPARISON RESULTS OBTAINED IN THE FRAMEWORK OF THE EC DIREC- TIVE 779/80 CEE ON SO2, BLACK SMOKE (BS) AND TOTAL SUSPENDED PARTICULATES (TSP).CALIBRATIONS AND MEASURING METHODS USED IN NATIONAL LABORATORIES WERE COMPARED TO THE REFERENCE METHODS LAID DOWN IN THE DIRECTIVE. TO THIS END, STANDARDS OF AIR-SO2 MIXTURES AT 40 AND 190 PPB SO2, BS AND TSP FILTERS AT DIFFERENT DARK- NESS LEVEL AND LOAD HAVE BEEN CIRCULATED AMONG NUMEROUS LABORATORIES AND SOME MEASURING STATIONS. ON THE AVERAGE, 78% OF SO2 MEASUREMENTS CARRIED OUT IN LABORATORIES AND 21% IN NETWORK STATIONS WERE COMPARABLE WITH THE IMPROVED RE- FERENCE METHOD (TETRACHLORO-MERCURATE PARAROSANILINE). WERE THE DEVIATIONS EX- CEED THE TOLERANCE LIMIT OF +-6%, THIS WAS RATHER BECAUSE OF INAPPROPRIATE HAN- DLING OF THE CALIBRATION THAN BECAUSE OF POSSIBLE SHORTCOMINGS OF THE DIFFERENT METHODS THEMSELVES. IN CONTRAST, FOR BS, LARGEST DEVIATIONS WERE CAUSED BY DIFFERENCES IN CONFIGURATIONS OF FILTER/REFLECTOMETER AND OF THE CONVERSION CUR-VES, FOR TSP BY VARYNG THE TYPE OF FILTERS, BALANCE SENSIBILITY AND CONDITIONINGPROCEDURES BEFORE WEGHING.TO AVOID ANY DISCRIMINATORY STRINGENCY FOR THE DIREC- TIVE, THERE IS THE NEED, FOR THE MEMBER STATES, TO DEFINE MORE STRINGENT REFE- RENCE METHODS AND IMPLEMENT QUALITY ASSURANCE PROGRAMMES, ESPECIALLY IN THE NETWORKS.NA-NOT AVAILABL

Codage et protection des informations dans un système de transmission d'image fonctionnant en temps réel

Les critères de qualité d'un système téléphoto utilisé pour la transmission d'images digitalisées (iconiques ou graphiques) sont caractérisés par la minimisation du temps entre l'émission et la reconstitution complète de l'image avec une qualité psychovisuelle acceptable. Les images considérées sont du type iconiques à haute résolution (20 ppmm). Du fait de leur grande simplicité de mise en oeuvre, les systèmes de compression d'images à codage prédictif, du type MICD, sont particulièrement bien adaptés à la transmission en temps réel. Cependant, les taux de compression théoriques obtenus sont inférieurs à 3. Des modifications ont permis de tripler les performances du codage par MICD et d'obtenir ainsi des taux de compression comparables à ceux fournis par des méthodes globales : il s'agit de la compression par MICD adaptée,étendue (MICDAE). Malheureusement, ces systèmes se caractérisent par une vulnérabilité importante aux erreurs de transmission. La propagation d'erreurs bidimensionnelle -plus ou moins importante suivant la prédiction utilisée et le mode de codage binaire des informations à transmettre- ne permet pas, en général, une reconstitution correcte de l'image émise. Apres une description sommaire de la compression par MICDAE, les problèmes posés par le codage des informations de source, la vulnérabilité et la protection contre les erreurs de transmission ont été étudiés

Second European Quality Assurance Programme for Sulphur Dioxide, Black Smoke and Suspended Particulates Measurements

Abstract not availableNA-NOT AVAILABL

Another way of looking at plane-based calibration: The centre circle constraint

Abstract. The plane-based calibration consists in recovering the internal parameters of the camera from the views of a planar pattern with a known geometric structure. The existing direct algorithms use a problem formulation based on the properties of basis vectors. They minimize algebraic distances and may require a ‘good ’ choice of system normalization. Our contribution is to put this problem into a more intuitive geometric framework. A solution can be obtained by intersecting circles, called Centre Circles, whose parameters are computed from the world-to-image homographies. The Centre Circle is the camera centre locus when planar figures are in perpective correspondence, in accordance with a Poncelet’s theorem. An interesting aspect of our formulation, using the Centre Circle constraint, is that we can easily transform the cost function into a sum of squared Euclidean distances. The simulations on synthetic data and an application with real images confirm the strong points of our method