Think of it as a simpler problem, a 2-Dimensional problem.

In 2-Dimensions you know you have an x-coordinate and a y-coordinate. You use these coords to draw the position of your entity (or virtual tour guide). Within a 3-Dimensional space, you still have the same x and y coordinates, with the addition of the z-coordinate. For the time being, ignore this additional axis.

To draw the world in 3 dimensions, you need to already know your location. It's where everything is drawn in accordance to your point of view. You can't have 3 or even 2 dimensions unless you already know the coordinates (location) of any item.

So how are you handling it? In a 2-Dimensional world I would already have an int (or floating point) of my location in the form of xPos and yPos. I'd then code a couple methods to set my xPos and yPos and another couple methods to return my current x and y position.

Using these methods I can then draw and/or retrieve the location of my entity at any time.

In order to place anything within your 3-Dimensional space you will already have to have an xPos yPos and zPos for any entity within that world. You have to have those three positions in order to exist within a space, don't you? And if you've already got those coded, you've got an easy way of returning them.