Chrono Trigger map?

After finishing this great game, and being a loyal fan to Chrono Trigger all these years, I was disappointed with the lack of geographical explantion as to where the land used in Chrono Trigger is, in Chrono Cross (from Square and from the general internet).

With all the references to Porre, the land is obviously still there so i'm just curious as to where it actualy is. My thoughts is that it is at the top left-hand corner of the map where there is a river which you cannot go up.

I just wish there was a map with some context or some explantion on the subject. Can anyone help me out? Thanks