It's not possible with 100% accuracy, but you might get close. You can model the land easily, but not trees or buildings. If you're standing on a barren rock i

It's not possible with 100% accuracy, but you might get close. You can model the land easily, but not trees or buildings. If you're standing on a barren rock it's easy, since there are no obstructions. If it's a forested area (you get this info from satellite images), you probably can't see water, even though there's no land between you and it, except if you're standing on a cliff or something, so the trees don't bother you. If it's an urban area, you probably won't be able to determine whether you can see water, since there aren't really models for buildings available.