  Multispectral (MS) image panchromatic (PAN) sharpening algorithms proposed to
the remote sensing community are ever increasing in number and variety. Their
aim is to sharpen a coarse spatial resolution MS image with a fine spatial
resolution PAN image acquired simultaneously by a spaceborne or airborne Earth
observation (EO) optical imaging sensor pair. Unfortunately, to date, no
standard evaluation procedure for MS image PAN sharpening outcome and process
is community agreed upon, in contrast with the Quality Assurance Framework for
Earth Observation (QA4EO) guidelines proposed by the intergovernmental Group on
Earth Observations (GEO). In general, process is easier to measure, outcome is
more important. The original contribution of the present study is fourfold.
First, existing procedures for quantitative quality assessment (Q2A) of the
(sole) PAN sharpened MS product are critically reviewed. Their conceptual and
implementation drawbacks are highlighted to be overcome for quality
improvement. Second, a novel (to the best of these authors' knowledge, the
first) protocol for Q2A of MS image PAN sharpening product and process is
designed, implemented and validated by independent means. Third, within this
protocol, an innovative categorization of spectral and spatial image quality
indicators and metrics is presented. Fourth, according to this new taxonomy, an
original third order isotropic multi scale gray level co occurrence matrix
(TIMS GLCM) calculator and a TIMS GLCM texture feature extractor are proposed
to replace popular second order GLCMs.
