Pixel weed search

A single 20 megapixel photo has 20 million pixels. An orthomosaic image over a large area can be made up of thousands of photos – that’s a lot of pixels!  We can automate a search of all these pixels looking for the colours of target weeds.

This method might not find the last weed in an area, but it is a powerful visual aid to focus attention on weeds that may not be seen in a visual grid search. It can significantly speed up the process of detecting weeds.

Royal fern (Osmunda regalis) has a reddy-brown colour in autumn and becomes more visibly distinctive from raupo which turns white.  This provides a great opportunity to use colour analysis techniques.

The reddy-brown colours of a known royal fern are sampled as a reference to search for other pixels of the same colour (pixel=2cm).
Sites suspected to be royal fern detected by a colour analysis of pixels (scale 1:500)