GPS vs GLONASS Messages

IoT Modules LTE Standard Module
1

Hello,

I enabled both the GPGGA and GNGNS NMEA messages at a fix frequency of 5Hz, and I noticed 2 things about the output (below):

[2024-06-17 10:55:07:183_R:] $GPGGA,145507.20,4113.121383,N,08510.276051,W,1,07,0.9,271.1,M,-33.0,M,5E
[2024-06-17 10:55:07:183_R:] $GNGNS,145507.20,4113.121383,N,08510.276051,W,AAN,13,0.9,271.1,-33.0,V5B
[2024-06-17 10:55:07:383_R:] $GPGGA,145507.40,4113.121383,N,08510.276051,W,1,07,0.9,271.1,M,-33.0,M,58
[2024-06-17 10:55:07:383_R:] $GNGNS,145507.40,4113.121383,N,08510.276051,W,AAN,13,0.9,271.1,-33.0,V5D
[2024-06-17 10:55:07:581_R:] $GPGGA,145507.60,4113.121383,N,08510.276051,W,1,07,0.9,271.1,M,-33.0,M,5A
[2024-06-17 10:55:07:581_R:] $GNGNS,145507.60,4113.121383,N,08510.276051,W,AAN,13,0.9,271.1,-33.0,V5F
[2024-06-17 10:55:07:783_R:] $GPGGA,145507.80,4113.121383,N,08510.276051,W,1,07,0.9,271.1,M,-33.0,M,54
[2024-06-17 10:55:07:783_R:] $GNGNS,145507.80,4113.121383,N,08510.276051,W,AAN,13,0.9,271.1,-33.0,V51
[2024-06-17 10:55:07:983_R:] $GPGGA,145508.00,4113.121383,N,08510.276051,W,1,07,0.9,271.1,M,-33.0,M,53
[2024-06-17 10:55:07:983_R:] $GNGNS,145508.00,4113.121383,N,08510.276051,W,AAN,13,0.9,271.1,-33.0,V56
[2024-06-17 10:55:08:184_R:] $GPGGA,145508.20,4113.121381,N,08510.276054,W,1,07,0.9,271.1,M,-33.0,M,56
[2024-06-17 10:55:08:184_R:] $GNGNS,145508.20,4113.121381,N,08510.276054,W,AAN,13,0.9,271.1,-33.0,V53
[2024-06-17 10:55:08:384_R:] $GPGGA,145508.40,4113.121381,N,08510.276054,W,1,07,0.9,271.1,M,-33.0,M,50
[2024-06-17 10:55:08:384_R:] $GNGNS,145508.40,4113.121381,N,08510.276054,W,AAN,13,0.9,271.1,-33.0,V55
[2024-06-17 10:55:08:584_R:] $GPGGA,145508.60,4113.121381,N,08510.276054,W,1,07,0.9,271.1,M,-33.0,M,52
[2024-06-17 10:55:08:584_R:] $GNGNS,145508.60,4113.121381,N,08510.276054,W,AAN,13,0.9,271.1,-33.0,V57
[2024-06-17 10:55:08:784_R:] $GPGGA,145508.80,4113.121381,N,08510.276054,W,1,07,0.9,271.1,M,-33.0,M,5C
[2024-06-17 10:55:08:784_R:] $GNGNS,145508.80,4113.121381,N,08510.276054,W,AAN,13,0.9,271.1,-33.0,V59
[2024-06-17 10:55:08:985_R:] $GPGGA,145509.00,4113.121381,N,08510.276054,W,1,07,0.9,271.1,M,-33.0,M,55
[2024-06-17 10:55:08:985_R:] $GNGNS,145509.00,4113.121381,N,08510.276054,W,AAN,13,0.9,271.1,-33.0,V50

  1. The actual positioning data between the two NMEA messages are identical.
  2. The positioning data within a 1 second interval are also identical, even despite my fix frequency being 5Hz.

These observations are consistent among many different NMEA messages.

I understand that this modem (EG25-G) uses 4 satellite systems, so I will assume that the positioning data I am seeing is a result of some average across any available data. However, I am wondering why the data is the same between the two messages.

I have 2 questions:

  1. Will the data between these two messages always be identical? Is it just a matter of personal preference for which format I would like to receive?
  2. Will the data within a 1 second interval always be identical? What’s the purpose of higher fix frequency if the reported data is always the same?

Thanks!

2

Do you think your position should be changed?
Just the interval between vaccines, do you have a time-space wormhole? :slightly_smiling_face:

For detail please check
Quectel_EC2x&EG2x&EG9x&EM05_Series_GNSS_Application_Note_V1.4.pdf