Semantic Segmentation of Satellite images

I need advice on which toolset I should use to label satellite images. The satellite images in my dataset have been filtered such as to remove those with significant evidence of human activity. So I only have four or so classes. Vegetation, meadow, no vegetation, snow/ice and water body. The dataset I want to label is large and fairly diverse (reflects the entire USA). Any ballpark estimate of how many examples I would need. Sorry, I am a beginner; so …

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