I would like to create a small application that generates a map. For this I need to find out the natural relief ratio as we know it on earth.
Suppose I divide the altitute in a scale of 0 to 10---where 0 is the sea bottom---and suppose the map is divided into tiles. How likely is the subsequent tile to deviate from or remain as the previous one.

My assumption is that there are less mountains than they are oceans, and that the higher the altitude gets, the less likely is the neighbouring area to be equally high or higher.

I'd like to have some figures though, based on real data. Do you have any idea? I've been looking on the internet but didn't find what i wanted.