Can gpstest process raw gnss data?

[M]

Hello,

I was wondering if gpstest is able to process gnss data from any specific constellation (For example GLONASS), and provide a location fix (current lat and lon) based on the processed data?

[Sean Barbeau]

The position shown in the GPSTest app is computed by the chipset, so the user doesn't have control over which constellations are used.

However, when you log raw measurement data from GPSTest or GnssLogger to a file, you can use tools such as GNSS Analysis Tools (https://developer.android.com/develop/sensors-and-location/sensors/gnss#analyze) or some of the other tools listed at https://github.com/barbeau/awesome-gnss to control which measurements are used to compute the positions.

Sean

[M]

Thank you for your response.

1. So what I understand from your response is that gpstest cannot provide current location from a specific constellation (developer's choice) in real time on the android device, right?

2. Can you please guide me for the following scenario? In a region there is a lot of jamming happening on the GPS constellation. Every location based app is having serious issues as they cannot correctly show the current location of the user. The idea that comes to mind is trying to get the current location of the user from other constellations (such as GLONASS) by getting the raw GNSS data and processing theme in real time. How feasible is this (as there seems to be no implementation of it done before on android)? Are there any stable and reliable implementations done before that you are aware of (I've seen the GPS Compare which tries to get the location only based on GALILEO, but the code is old and not maintained and limited only to GALILEO)?

[Sean Barbeau (xWF)]

>1. So what I understand from your response is that gpstest cannot provide current location from a specific constellation (developer's choice) in real time on the android device, right?

Correct

>How feasible is this (as there seems to be no implementation of it done before on android)? Are there any stable and reliable implementations done before that you are aware of (I've seen the GPS Compare which tries to get the location only based on GALILEO, but the code is old and not maintained and limited only to GALILEO)?

There is an implementation of WLS in the open-source version of GnssLogger at https://github.com/google/gps-measurement-tools/tree/master/GNSSLogger. IIRC this currently uses all constellations, but could be modified to only compute positions based on certain constellations/bands.

You can check the open-source Android app section of https://github.com/barbeau/awesome-gnss, I might be forgetting another example.

Sean

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[M]

Thanks for your response.

Could you please guide me with the following situation?

I have collected the GNSS log using the GPSTest and GnssLogger android applications. What I want to do is to calculate the latitude and longitude of my device's position from these logs one constellation at a time. So I want to end up with four different latitude and longitudes which are from GPS, Glonass, Galileo and BeiDuo separately. My goal is to find out if GPS is being jammed in a given location by comparing these latitudes and longitudes.

1. Is this feasible using an android device as GNSS data collector?

2. How should I process the raw data to get the latitude and longitude? What tools should I use? What steps should I take?

[Sean Barbeau (xWF)]

I'd suggest starting with the GnssAnalysisTool here:

https://developer.android.com/develop/sensors-and-location/sensors/gnss#analyze

You can load logs from GnssLogger or GPSTest (GnssLogger focuses more on logging, so I'd use those logs personally). The measurements column will show a weighted least squares (WLS) position based on the constellations/signals that you have selected in the UI.

Sean

To view this discussion visit https://groups.google.com/d/msgid/gpstest_android/e5a4e0e0-30c7-4a58-91b3-0f41074f7556n%40googlegroups.com.

[M]

Hello. I have used the GnssAnalysis tool, and it doesn't seem to be able to calculate latitude and longitude based on a single constellation.

- Do you know any tools to calculate latitude and longitude of an Android device in real-time or at least in the same day, based on a single constellation?

- Is there any way to be able to calculate latitude and longitude (based on a single constellation) without the need for downloading ephemeris data or any other data, and only based on the raw GNSS log received by the Android device?

[NLTrams]

I've posted an answer (description how to use a single constellation in the GNSS Analysis tool) in the GIS Stack Exchange query thread here.