Radiomeric and Geometric Analysis of Worldview-2 Stereo Scenes

WorldView-2 (WV-2) is DigitalGlobe's latest very high resolution optical sensor. Launched on October 8, 2009, and fully operational since January 5, 2010, it flies along a sun-synchronous orbit at an altitude of 770km. The sensor is able to acquire panchromatic imagery at 0.46m ground resolution (0.52m at 20° off-nadir) and multispectral images in eight spectral bands at 1.8m resolution. In addition to the four typical multispectral bands (blue, green, red, near infrared), the sensors scans the coastal (400450nm), yellow (585-625nm), red edge (705-745nm) and near infrared-2 (860-1040nm) bands. Stereo images can be planned thanks to the ability of the sensor to rotate off-nadir up to +/-45°. This paper describes the preliminary analysis on WV-2 carried out at the EU Joint Research Center (JRC) in Ispra (Italy) by the ISFEREA Team of the Institute for the Protection and Security of the Citizen (IPSC), and in collaboration with the Bruno Kessler Foundation (FBK) in Trento (Italy). The purpose of the study is to evaluate the radiometric and geometric properties of the sensor and its potentials for 3D information extraction. The images used for the analysis are a stereopair over North-West Italy, where ISFEREA is establishing a testfield. The radiometry of the images is evaluated through different methods, including the estimation of the noise level (standard deviation of the digital number) in homogeneous and non-homogeneous areas. The images are oriented with RPC-based approach: using some GCP (ground control points), the given Rational Polynomial Coefficients (RPC) are improved with an affine transformation to compensate residual systematic errors. For automatic 3D information assessment, a Digital Surface Model (DSM) is generated with the SAT-PP software package and 3D building models are extracted semi-automatically with the CyberCity-Modeler (CCM) package. The methodology and preliminary results are described and discussed.