Scale vs pixels

[Ghostman]

Select the area of the island, color-fill it with black, invert selection and color-fill the rest of the picture with white. Then use the histogram to count the number of black (value == 0) pixels.

You can then calculate the area (in square kilometers) of a single pixel by dividing 600,000 km2 by the total number of pixels to the island.

[Gidde]

Select the area of the island, color-fill it with black, invert selection and color-fill the rest of the picture with white. Then use the histogram to count the number of black (value == 0) pixels.

You can then calculate the area (in square kilometers) of a single pixel by dividing 600,000 km2 by the total number of pixels to the island.

This is exactly what I do to figure out scale.