I want to know more! It seems like there are areas around the canoe which have similar appearance in the gray scale are these water chestnut areas too? Is the water chestnut the black areas in the gray scale image and there are just different densities of water chestnut? Very cool. Would love to hear more. Thanks for sharing. Is this the Warner Lake where the images are from:

https://maps.google.com/maps?q=Warner+Lake,+Massachusetts&ll=42.387966,-72.56916&spn=0.022537,0.045447&client=firefox-a&hnear=Lake+Warner&t=h&z=15

I think the only areas in the image with waterchestnut present are within the white circles. Other areas that are dark in the classification result (grayscale image) are false positives. This was Ned's first try training his magic routines to identify waterchestnut, so the result could get better. You found the correct Lake Warner.

This isn't actually a classification. I was generating different layers from the 4-band (red, green, blue, near-IR) images collected a few weeks ago to improve classification results and this is one of the images that was created. The generated images included band subtractions, band ratios like NDVI, texture images, and principal component images. The black and white image in Chris' animation is the 4th principal component image derived from the 4-band image. If this highlights water chestnut it's shear luck. I still need to run some experiment with other images (I've only tried two so far) with different resolutions. My expectation is that at the very least this will be an important layer to add to the classification but it might actually be a quick and dirty way to create a nice overview of likely water chestnut areas. An option for creating principal component images can be added to the plugin if there's an interest.

This looks very encouraging as a possible tool for those of us trying to locate and control water chestnut. Since I haven't been involved since the day in the field when the photos were taken, I am wondering if the GPS points taken of water chestnut were used to verify these locations identified in the photo classification.

Hi Cynthia, We got several GPS locations from patches of water chestnut, but I have not yet matched up the field descriptions with the GPS coordinates (I am not sure which field sheet goes with which coords). However, this is not very critical because we have lower altitude photos in which you can clearly distinguish water chestnut from everything else growing there. So we know exactly where it is in many of the photos. Ned is now focusing on the task of machine identification, and we can use the photos as confirmation.

I am interested to hear whether you and Nate and Colleen think you harvested all of the water chestnut circled in the photo above and in the other photos here.