How do I do to calculate the % of sea and lands ?

[Naima]

How do I do to calculate the % of sea and lands on my map ? I using an equirectangular map that I can project orthographically ... so I guess things woudl change on a sphere .

[waldronate]

Use an equal-area projection such as sinusoidal and use a piece of software to count the number of pixels above water and below water. For example, using Fractal Terrains and Photoshop:
1 ) make a coloring scheme where the land is white and the sea is black, all with no shading
2 ) change projection to sinusoidal (other equal-area projections such as Wagner VII, Hammer, or Albers Equal-Area Conic would also work).
3 ) zoom so that the entire world is visible. Having a square viewing area in FT and good margins around the edges will reduce the likelihood of clipping on export.
4 ) save the image as a PNG to ensure that the non-world areas will be transparent; alternatively, set the background color to something that will be easy to remove like magenta.

All further steps take place in Photoshop:

5 ) open the saved image in Photoshop.
6 ) open the histogram window (ensure that "expanded view" is on)
7 ) select the sea color and the land color (should be all active pixels on the map).
8 ) note the total number of pixels in the histogram window (enable the uncached histogram if necessary).
9 ) select just the sea color
10 ) note the number of pixels in the histogram window (enable the uncached histogram if necessary).
11 ) calculate 100*(sea pixels count / total pixels count) as the sea percentage.
12 ) calculate 100*((total pixels count - sea pixels count) / total pixels count) as the land percentage.

[Naima]

Thanks ...

result ....

100*(227416/320591)=70.93648917156127

Yeah It seems I got by look the exact % I wanted on my world so no need to change anything ....