# Improving IMES Localization Accuracy by Integrating Dead Reckoning Information
## 6 Positioning Experiments
### Pedestrian Localization  
#### 6.2.1 Experimental Setup  
In this experiment, a human subject held an IMES receiver antenna and a motion sensor that includes a three-dimensional accelerometer and a three-dimensional gyroscope (the motion sensor's sampling rate is 100 Hz). The subject was asked to walk at a speed of 300 mm/s while following the pre-defined figure-eight path shown in Figure 8 fifteen times, and an actual path was measured by the laser range finder as, is the case in the robot localization setup. The reason that the number of round trips was three-times more than the case of robot is because the moving velocity of the human subject was about three-times higher than that of the robot. The height of the IMES receiver antenna was set at approximately-800 mm from the floor, which was assumed to be the height of a subject's waist.  
The PDR information of the relative distance and orientation angle was calculated with the six-dimensional acceleration measurement. Particularly, the relative distance (displacement in an epoch) was calculated with the the number of steps of the subject and his or her stride length. In this case, the sampling rate of the IMES receiver (10 Hz) is higher than the subject's step rate (1.5-4 Hz); to cope with this, one step was divided into several portions for each corresponding to 100 ms in the post-processing and used for the prediction process of the Kalman filtering. In order to obtain the relative orientation (angular displacement in an epoch), the rotational velocity was acquired from the gyroscope of the motion sensor and it was integrated for 100 ms.  
The parameters of the EKF were set as follows. For the initial values of the state vector, \(\mathbf{X}\), described in Equation (18), (\(-500\) mm, \(-1000\) mm and \(0^{\circ}\)) were set as the correct initial position/orientation, and (\(-1000\) mm, \(0\) mm and \(-45^{\circ}\)) were set as incorrect values. For the initial values of the error covariance matrix, \(\mathbf{P}\), in both the cases of the correct and incorrect initial values, (4,000,000, 4,000,000, 1) were set to the diagonal elements and zero was set to the off-diagonal elements; this means that the uncertainty of the estimated state are \(x\) = 2000 mm, \(y\) = 2000 mm, and theta = 1 radian as their standard deviation. The values of the x- and y-coordinates are larger than the case of the robot experiment above. This is because the position estimation error of pedestrians is larger than that of the robot. The system noise covariance matrix, \(\mathbf{\Omega}\), shown in Equation (18), were set as \(\mathbf{\Omega}[0][0]=2.28\), \(\mathbf{\Omega}[1][1]=2.28\), \(\mathbf{\Omega}[2][2]=0.000001\), and all off-diagonal elements were set to 0. As is the case of robot, these values were determined empirically based on several dead reckoning results so that a good EKF estimation result could be obtained. The observation noise covariance matrix, \(\mathbf{\Psi}\), shown in Equation (20), were set as \(\mathbf{\Psi}[i][j]\) = 386,001 (\(i=j\)) and \(\mathbf{\Psi}[i][j]\) = 0 (\(i\
eq j\)). This is the same as the case of the robot experiment.