# Sensor's normal location

**URL:** <https://mne.discourse.group/t/sensors-normal-location/5280>\
**Category:** Support & Discussions\
**Created:** [July 17, 2022, 4:36am UTC](https://mne.discourse.group/t/sensors-normal-location/5280 "2022-07-17T04:36:44Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![tPPMc-cs](https://yyz2.discourse-cdn.com/free1/user_avatar/mne.discourse.group/tppmc-cs/32/1034_2.png) [@tPPMc-cs](https://mne.discourse.group/u/tPPMc-cs)\
**Post date:** [July 17, 2022, 4:36am UTC](https://mne.discourse.group/t/sensors-normal-location/5280/1 "2022-07-17T04:36:45Z")

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Hi,  
The documentation on the info object states that ‘loc’ stores “position  
plus the normal given by a 3x3 rotation matrix”.

But I’m still confused how to get the normal of sensors, I tried as below:

1. concatenate the 3x3 rotation matrix with sensor’s location to get 3x4 matrix, then concatenate with [0, 0, 0, 1] to get the ultimate rotation matrix of 4x4 dimension
2. then np.dot(rotation matrix, sensor’s location)

my question is: is my rotation matrix right? and is the rotation matrix is from sensors coordinate to device coordinate?

Thanks  
Teddy