Once the database has been collected and processed, the indoor environment is ready to support location-based AR on the mobile phone. As we will see in Section 5, having a coarse estimate of the pose makes the image retrieval step easier and accelerates the pose estimation algorithm. In this work, we used the N97 phone from Nokia. It has several sensors to help us with the pose estimation such as GPS, an accelerometer, a magnetometer and a rotation sensor. First, when considering cell phone pose estimation, we