I'm building an indoor wifi-based tracking system that can calculate the position of a device in meters relative to the sensors distributed throughout the building. So far I've gotten to the point where I have the ability to sense the device and trilaterate its position on an arbitrary x-y grid (in meters) where the sensor locations are known, but now I need to output that to Google Maps for display. I'm stuck trying to figure out how to convert this system to latitude and longitude, and be accurate to within a meter. I've seen some estimations people have used for such applications, but they're plotting on a much larger scale so an error of 10m or so is acceptable. In my case, 10m would make the data completely unusable.
Is there an easy way to make this conversion? I can find the lat/lon of the sensors, but I don't know where to go from there. My equations are based on a point-coordinate system, so I can't use a vector system or other method without redesigning everything.