function ScrollMap() {

	var self = this;
	scrollN.onclick = function() {self.scroll(ScrollMap.NORTH);}
	scrollE.onclick = function() {self.scroll(ScrollMap.EAST);}
	scrollS.onclick = function() {self.scroll(ScrollMap.SOUTH);}
	scrollW.onclick = function() {self.scroll(ScrollMap.WEST);}
}

ScrollMap.NORTH = 1;
ScrollMap.EAST = 2;
ScrollMap.SOUTH = 3;
ScrollMap.WEST = 4;

ScrollMap.STEP = 200;

ScrollMap.prototype.scroll = function(dir) {

	var x = parseInt(baseRect.style.left);
	var y = parseInt(baseRect.style.top);

	switch (dir) {
		case ScrollMap.NORTH:
			if (y >= 0)
				return;
			y += ScrollMap.STEP;
			if (y > 0)
				y = 0;
			break;
		case ScrollMap.EAST:
			if (x <= -493)
				return;
			x -= ScrollMap.STEP;
			if (x < -493)
				x = -493;
			break;
		case ScrollMap.SOUTH:
			if (y <= -620)
				return;
			y -= ScrollMap.STEP;
			if (y < -620)
				y = -620;
			break;
		case ScrollMap.WEST:
			if (x >= 0)
				return;
			x += ScrollMap.STEP;
			if (x > 0)
				x = 0;
			break;
	}
	moveBaseRect.to(x, y, 20, false);
}