Pre-processing of Remotely Sensed Imagery

A common obstacle to the use of remote sensing data for nature conservation is the difficulty in obtaining or generating data that are pre-processed to a standard that gives confidence in their subsequent use. Such processing is essential in order to facilitate physical measurement (e.g., of temperature, surface reflectance, height) and compare data (e.g., reflectance or radar backscatter) acquired for different dates or areas. For optical and radar data, this pre-processing includes orthorectification, calibration, atmospheric and topographic correction and, in the case of LiDAR, ground return classification and surface height retrieval. This chapter therefore provides an overview of the common pre-processing steps that are undertaken or needed in order to create what has been recently termed an analysis ready data (ARD) product. Increasingly, such products are being provided routinely to minimize the effort of data users but knowledge of how this is achieved is important in determining the integrity and understanding the use of the data. The information provided should help users to identify, select and use data with confidence or to perform their own processing of the raw data.