Targets, methods, and sites for assessing the in-flight spatial resolution of electro-optical data products

The spatial resolution of a digital, electro-optical remote sensing imaging system or product is an important image quality characteristic that helps determine the utility of an imaging source. Although spatial resolution is often described by a single image quality parameter, the ground sample distance, there are several other parameters that affect image sharpness and need to be considered. These other parameters are associated with the point-spread function, signal-to-noise ratio, and dynamic range of the image product. This review paper covers the various approaches to in-flight measurement of spatial resolution parameters, including ground sample distance, point spread function, optical transfer function, modulation transfer function, far field response, and edge response and their significance, as well as target types and methods to determine these spatial resolution parameters. To this end, the paper lists and describes various targets found across the world, as well as astronomical ones. These targets are appropriate for evaluating a wide range of image scale products. For high spatial resolution imaging systems, the types of targets range from engineered fixed and deployable targets to agricultural and urban features, allowing almost any site to be used for determining spatial resolution. Independent, comprehensive image product evaluation sites that are currently in use in the US and Europe are also described.