  With inputs from RGB-D camera, industrial camera and wheel odometer, in this
letter, we propose a geometry-based detecting method, by which the 3-D
modulated LED map can be acquired with the aid of visual odometry algorithm
from ORB-SLAM2 system when the decoding result of LED-ID is inaccurate.
Subsequently, an enhanced cost function is proposed to optimize the mapping
result of LEDs. The average 3-D mapping error (8.5cm) is evaluated with a
real-world experiment. This work can be viewed as a preliminary work of visible
light positioning systems, offering a way to prevent the labor-intensive manual
site surveys of LEDs.
