The three channels were first filtered to reduce
noise. Typical IKONOS noise is (a) chess pattern
noise (common for satellite sensors, increased through
sharpening included in MTFC) and (b) vertical stripes,
usually dark but sometimes bright (again typical for
linear CCD arrays). A 33 low-pass filter, empirically
determined and asymmetric (stronger smoothing
in horizontal direction to account for the vertical
stripes, was used. The filter coefficients were: