> For the complete documentation index, see [llms.txt](https://guides.geospatial.bas.ac.uk/spectral-analysis-of-imagery/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://guides.geospatial.bas.ac.uk/spectral-analysis-of-imagery/mixed-pixels.md).

# 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![Image: P Fretwell unpublished](https://2016800125-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FpQSDh3IPyvK1x3GCRlei%2Fuploads%2Fz2MHx8PSPq6cDtWRwrzu%2Fwhale1.jpg?alt=media\&token=d3e0798b-9427-44a8-be96-6a99cba0d7b5)

![Image: P Fretwell unpublished](https://2016800125-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FpQSDh3IPyvK1x3GCRlei%2Fuploads%2FpnOWakM2dfPRzjdgstTX%2Fwhale2.jpg?alt=media\&token=dfe40f7b-b1e0-4ecc-95a5-b5843abe4e17)