GPS accuracy

[Shanmukh Araveeti]

Hi Team,

I just want clarity on 2 points related to accuracy of nRF9151 GPS.

1) As shown in datasheet, "Positioning accuracy (CEP50), periodic tracking" is 3.4m. So that means only 50% of the time device will be able to track the location within 3.4 meters and remaining 50% of the time it will be outside of the 3.4 meters. Please let me know if this is correct understanding or not. If correct than is there any accuracy number associated with CEP100 or any other higher CEP value?  

2) Secondly datasheet mentions accuracy numbers for 2D fix. I want to know the accuracy numbers related to 3D fix. and also does nRF9151 supports 3D fix or not? 

Regards

[Amanda Hsieh]

Hi, 

1) Yes, this is the correct interpretation. In other words, CEP refers to the radius of a circle in which 50% of the values occur. 

Here is more detailed results from a test that is done with similar ideal assumptions as the data sheet test. This should not be understood as a guarantee that this performance can be consistently achieved but can be used for illustrative purposes only!  68 means "CEP68" etc. "Max" would be the "CEP100" that was achieved in this particular test. It is not realistic to make promises about CEP100 in product specification due to non-deterministic nature of GNSS position accuracy especially in challenging environments.

2) nRF9151 always outputs a 3D fix. It's just that most customers are only interested in the latitude and longitude of the fix and therefore we don't provide this data in the product specification. The altitude component of the fix is less accurate dues to GPS system design. 

---

I would like to remind that all the numbers I presented (as well the product specification values) are obtained in ideal conditions (high quality roof top antenna, stable room temperature etc.). I encourage you to get hold of nRF9151 development kit and test for yourself to get a very realistic understanding about the performance in your particular use case!

Regards,
Amanda H.

[Shanmukh Araveeti]

Hi Amanda,

Thanks for your quick response.

1) What is STD value in the table?

2) So, how I can get 2D fix as it seems that 2D fix has less error than 3D fix. 

( I do understand readings provided by you and in product specification sheet are taken in ideal condition).

3) The readings which you shared are based on standalone or A-GPS and taken in periodic or continuous mode. Please let me know.

Regards,