Tracker V2 GPS accuracy

[Gerbert]

Hi,

We are currently evaluating the Tracker V2 application.

We would like to increase GPS accuracy, before the nrf9160 returns status GNSS_EVT_DATA_READY. No problem if gaining GPS accuracy will take a bit longer.

Can we change GPS accuracy parameters/criteria? For example the GNSS needs to track at least 6 satellites to produce a fix, instead of just 4.

Thanks. 

[Håkon Alseth]

Hi,

 

ATv2 in current tagged versions (including v2.1.0) has a limited option to configure the GNSS, unfortunately.

However, in future tagged versions, it will start to use the location module:

https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/libraries/modem/location.html

Which is enabled with this commit:

https://github.com/nrfconnect/sdk-nrf/commit/8b2c475ed7368aaac606af4c53885009331ae35a

  

With the location module, you can set the accuracy of your requested GNSS signal to low/normal/high:

https://github.com/nrfconnect/sdk-nrf/blob/v2.1.2/samples/nrf9160/location/src/main.c#L152

Kind regards,

Håkon

[Gerbert]

Thanks. I have found some brief explanation:

	/** @brief Desired accuracy level.
	 *
	 * @details If accuracy is set to LOCATION_ACCURACY_LOW, GNSS relaxes the
	 * criteria for a qualifying fix and may produce fixes using only three satellites.
	 *
	 * If accuracy is set to LOCATION_ACCURACY_HIGH, instead of using the first fix, GNSS is
	 * allowed to run for a longer time. This typically improves the location accuracy.
	 */

Can you explain how "run for a longer time" is handled? Is it only time based (eg running +5s after first fix) or are there also other GNSS KPI's involved (eg HDOP, etc)?

[Håkon Alseth]

Hi,

 

It does not filter on DOP, but allows the GNSS to run longer, which in most cases improves the accuracy of the fix.

The location API allows you to set the amount of consecutive fixes in the configuration struct that is passed to the library:

https://github.com/nrfconnect/sdk-nrf/blob/v2.1.2/samples/nrf9160/location/src/main.c#L102

In this case, it loads the default configuration, which is _ACCURACY_NORMAL:

https://github.com/nrfconnect/sdk-nrf/blob/v2.1.2/lib/location/location.c#L130

 

In _LOW and _NORMAL mode, the "num_consecutive_fixes" member has no effect, as per the API documentation:

https://github.com/nrfconnect/sdk-nrf/blob/v2.1.2/include/modem/location.h#L178-L184

 

Kind regards,

Håkon