
3
Transformations
Thus far we have thought of multispectral and SAR imag es as three-dimens ion-
al arrays of pixel intensities (columns × rows × bands) representing, more or
less directly, measured radiances. In the present chapter we consider other,
more abstract representations which are useful in image interpretation and
analysis and which will play an important role in later chapters.
The discrete Fourier and wavelet transfo rms that we treat in Sections 3.1
and 3.2 convert the pixel values in a given spectral band to linear c ombina-
tions of orthogonal functions of spatial frequency and distanc e. They may
therefore be c lassified as spatial tr ...