Microscopes use a scale bar. Never trust the magnification factor (e.g., "40x") for true measurement, as monitors stretch images.
When a scientist calculates deforestation or the area of a wildfire scar, they count the number of “burned” pixels and multiply by the pixel value in mm² (or m²). A forest fire covering 500,000 pixels in a Landsat image means the actual burned area is 500,000 × 900 m² = 450 km². pixel value mm2
If you take an image and simply count the number of pixels covering an object, you get a number called "Pixel Area." This is arbitrary. If you zoom in, the pixel count goes up, but the object hasn't physically grown. To fix this, you need a . Microscopes use a scale bar