High-resolution Satellite Imagery: a Review of Metric Aspects

With the era of commercial high-resolution earth observation satellites having dawned with the launch in September, 1999 of Ikonos-2, it is imperative that there is an understanding in the photogrammetric and remote sensing communities of the full metric potential of high-resolution satellite line scanner imagery. This paper discusses the metric exploitation of 1m satellite imagery, and specifically looks at the options available for multi-image restitution in situations where optimal ground point triangulation accuracy is sought. Such applications would include automated DTM generation and highaccuracy feature determination for both mapping and geopositioning. The paper commences with a brief discussion of accuracy aspects and then overviews the collinearity model for orientation/triangulation of line scanner imagery. Alternative restitution models are then reviewed. These include rational functions, the direct linear transformation and an affine projection approach. Each restitution model has its merits and limitations, and of central importance is the provision or lack of provision of the ‘camera models’ for the different high-resolution satellite systems. With the prevailing level of uncertainty over just what critical sensor calibration information will be made available by the satellite imaging companies, there is consequently a need for a range of alternative, practical approaches for extracting accurate 3D terrain information from 1m satellite imagery.