# Calculate covariance matrix from x,y,z data of /odom

I've recorded a bag file from a custom robot (in real world) that does not provide covariane matrix and I want to use `/odom`

to feed an `ekf`

, but covariance matrix is 0. How can I calculate it?

It's a sample of `/odom`

:

```
pose:
pose:
position:
x: 0.082
y: 0.507
z: 0.0
orientation:
x: 0.0
y: 0.0
z: -0.789272088731
w: 0.614043622188
covariance: [0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
twist:
twist:
linear:
x: 0.104
y: 0.0
z: 0.0
angular:
x: 0.0
y: 0.0
z: 0.0663225115758
covariance: [0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
```

which package you are using? Your question may help me in some points. I am also facing same problem. I want to use robot_localization package.