Mixed pixels

Remote sensing image sensor collect energy, which is sampled on to a grid of pixel data.

Given the heterogeneity of the surface of the earth and the objects we wish to analyse and identify, it is rare that a single object will match exactly to our grid of pixels in the data.

These images below illustrate this. The first image is showing a whale, with the equivalent image pixel grid overlaid. The second image shows that only a handful are pure whale pixels (dark blue), with the remainder being mixed pixels.

It is important to consider the presence of mixed pixels when conducting spectral analysis.

Image: P Fretwell unpublished

Image: P Fretwell unpublished