I have a satellite image. I want to sample all the trees and vectorize them at once

Question

I have a satellite imagery. I want to vectorize all the trees at once by color sampling. How to do it?

I used Photoshop to sample the all the various color ranges of trees [Green] to distinguish between trees and built-up area. Can I use this technique as the Photoshop converted the trees in satellite image in one colour. As you can see in this image I sampled all the trees and converted to black colour to distinguish between trees and built-up area. Now can I select this color from this image and convert it to a VECTOR for Land use and Land cover map in QGIS.

Answer 1

Yes you can. You have a few options.

1. If you have a new raster layer in which all of the trees are now colored black you could use a reclassify tool to produce a new raster such that all of the trees have a value of 1 and all of the non-tree pixels have a value of 0. Then polygonize that result. See this link for more help on reclassifying options.

2. Have a look at the semi-automatic classification plugin in. This approach would save you a Photoshop processing step in the first place and likely retained any spatial information that was contained in the original data. https://fromgistors.blogspot.com/p/semi-automatic-classification-plugin.html