Resumo:A extração de informações geoespaciais de uma imagem orbital requer a orientação interior e exterior da mesma. Os parâmetros de orientação exterior (POE) podem ser obtidos de forma direta, utilizando sensores GNSS/INS e estelares, ou indireta, utilizando feições de controle no espaço objeto. Os parâmetros de orientação interior (POI) são inicialmente obtidos por calibração em laboratório antes do lançamento do satélite, e podem também ser estimados periodicamente pela calibração geométrica em órbita. O objetivo deste trabalho foi realizar a calibração geométrica em órbita do sensor HRC-CBERS 2B. Para tanto, foram consideradas as correções dos efeitos sistemáticos causados pela geometria do plano focal do sensor e pelo sistema de lentes do mesmo. Uma densa quantidade de pontos de controle e verificação foi utilizada, sendo que a análise da exatidão planimétrica nos pontos de verificação foi aplicada para avaliar a calibração. Quatro experimentos foram realizados analisando três diferentes conjuntos de POI. Os resultados dos experimentos de calibração foram muito próximos, não apresentando diferenças significativas. Uma maior exatidão foi obtida quando se empregou o grupo de POI modelando a translação, rotação, fator de escala e flexão das matrizes de CCD (Charge-Coupled Device), juntamente com a distorção radial simétrica do sistema de lentes.Palavras-chave: modelo UCL, câmara HRC, calibração geométrica em órbita. Abstract:The geospatial information extraction from orbital images requires the internal and external orientation. The external orientation parameters (EOPs) can be obtained directly from GNSS/INS and star sensors, or indirectly by control features in the object space. The interior orientation parameters (IOPs) are first determined from laboratory calibration process prior the satellite launch, and can be estimated by the periodically on-orbit geometric calibration. This paper aimed to perform the on-orbit geometric calibration of the HRC-CBERS 2B sensor. The corrections of systematic effects caused by the focal plane of the sensor and by lens system were

In this paper a novel model to orient a pushbroom linear optical satellite image is proposed. This one is based in the adaptation of the Orbit-Attitude model for use of the Modified UCL Kepler platform model. It has only the components of satellite position and velocity as unknowns. This implies not only the reduction of unknowns but also the elimination of initial adjustments of the orbit to estimate the polynomial parameters. In order to validate the model, four experiments were conducted using one HRC-CBERS 2B image. Two distributions of ground controls points (GCPs) were tested, 70 and 35 GCPs. A quantity of 43 check points (CPs) was used to analyze the planimetric accuracies of the orientations. For comparisons purpose the image was also oriented with platform model using 2 nd order polynomial. The results showed that the planimetric accuracy difference in the use of the two models is 4 and 6 centimeters in the two mentioned configurations of GCPs, respectively. However, the main advantage of applying the proposed model is the direct use of ephemeris without the necessity of interpolations and preadjustments, which makes the orientation process simpler.

Synchronization of airborne laser scanning devices is a critical process that directly affects data accuracy. This process can be more challenging with low-cost airborne laser scanning (ALS) systems because some device connections from off-the-shelf sensors are less stable. An alternative to synchronization is performing a postprocessing clock correction. This article presents a technique for postprocessing synchronization (off-line) that estimates clock differences based on the correlation between the signals from the global navigation satellite system (GNSS) trajectory and the light detection and ranging (lidar) range, followed by refinement with a least-squares method. The correlation between signals was automatically estimated considering the planned flight maneuvers, in a flat terrain, to produce altimetric trajectory variations. Experiments were performed with an Ibeo LUX laser unit integrated with a NovAtel SPAN-IGM-S1 inertial navigation system that was transported by an unmanned aerial vehicle (UAV). The planimetric and altimetric accuracies of the point cloud obtained with the proposed postprocessing synchronization technique were 28 cm and 10 cm, respectively, at a flight height of 35 m.