The radiometric normalization of multitemporal Thematic Mapper imagery of the midlands of Ireland - a case study

Two Landsat Thematic Mapper (TM) scenes of the same area of the midlands of Ireland were required to be radiometrically normalized. Standard techniques were reviewed and considered unsuitable. A hybrid approach was adopted that used linear transformation functions. As part of this approach, a novel thresholding-based method for extracting reference data from a land cover class with sub-pixel scale elements was developed. This method was shown to be robust with a consistency of ca ±1 digital number (DN) being achievable in the extracted reference data. A procedure for removing pixels influenced by thin cloud and associated shadow was included. The radiometric normalization approach produced acceptable Root Mean Square Errors in the range 0.8-2.5 DN. Whereas the strategies and methodologies developed were appropriate to the particular environment, the developmental process may serve as a template for analysts working in similar environments elsewhere.