Avaliação da geometria do produto Ikonos Geo / Geometric evaluation of Ikonos Geo product

Eloy de Souza Silva

Geometric correction of satellite images is relevant to cartographic applications and to integrate these images in geographic information systems. Image correction consists in the distortion elimination, caused by the sensor and by the observed object, through models of image geometry and ancillary information such as digital terrain model and control points. In this work it was sought to correct an Ikonos image in its most basic level (Geo product) and evaluate the achieved quality. A rational polynomial model with 20 coefficients was used and it was observed that with this model it was possible to generate an image compatible to a chart with a scale of 1:10,000, class A (PEC). The model quality evaluation was performed not only by the mean square error, but also through the overlap of the vectors coming from the photogrammetric restitution. It was observed that a good adjustment of the vector over the corrected image does not keep a relation to the mean square error of the model used to correct the image. Factors such as distribution and quantity of point controls could not be analyzed in depth due to the limited number of points. It was conclude that it is possible to obtain results at cadastral scales (1:25,000 or larger) from Ikonos products that are financially more accessible and with a less complex image geometry model (20 coefficients) than the rational polynomial model adopted by Space Imaging (80 coefficients). Another important conclusion is that the mean quadratic error by it self is not a good global quality indicator of geometric correction; whenever possible, the vectors should be used to evaluate, with greater rigor, the final product.

Avaliação da geometria do produto Ikonos Geo / Geometric evaluation of Ikonos Geo product

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