Hello!
I am working with GPS and the shield for the first time. Attached is a screenshot of some data that was parsed using the "Adafruit_GPS" library and the appropriate example code.
– Can somebody explain to me, why the quality changed from 0 to 2 indicating a change from invalid to DGPS, when I cannot see an obvious change in the sentence itself?
– Does it have to do with the checksum at the end or something?
– Is the data really invalid? Why, since nothing really changed?
– Can the module use DGPS? Where does the reference come from?
This change occurred approx. 10 mins after the fix.
Thanks in advance.
Ultimate GPS Logger Shield – Confusion about correct fix
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- sp100
- Posts: 2
- Joined: Tue Nov 10, 2015 5:32 pm
Ultimate GPS Logger Shield – Confusion about correct fix
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- GPS_data
- Bildschirmfoto 2015-11-10 um 22.37.53.png (52.81 KiB) Viewed 286 times
- adafruit_support_mike
- Posts: 67485
- Joined: Thu Feb 11, 2010 2:51 pm
Re: Ultimate GPS Logger Shield – Confusion about correct fix
You seem to be comparing the $GPGGA sentences to the $GPRMC sentences. That doesn't work. The fields have different meanings.
The value after 'E' in the $GPRMC sentence is actually 0.02, which is ground speed in knots.
This page has a breakdown of NMEA sentences and what they mean:
http://www.gpsinformation.org/dale/nmea.htm
The value after 'E' in the $GPRMC sentence is actually 0.02, which is ground speed in knots.
This page has a breakdown of NMEA sentences and what they mean:
http://www.gpsinformation.org/dale/nmea.htm
- sp100
- Posts: 2
- Joined: Tue Nov 10, 2015 5:32 pm
Re: Ultimate GPS Logger Shield – Confusion about correct fix
Thanks for the fast reply. I am very sorry for making this not clear enough. I was referring to the GGA sentence where after time, latitude, longitude comes fix and then number of satellites. Which in my attachment is fix = 2 and satellites = 9 all the time.
In the RMC sentence is A for active all the time also. So I want to understand, where the change in the parsed information comes from? And how DGPS is possible?
Does this make more sense now?
In the RMC sentence is A for active all the time also. So I want to understand, where the change in the parsed information comes from? And how DGPS is possible?
Does this make more sense now?
- adafruit_support_mike
- Posts: 67485
- Joined: Thu Feb 11, 2010 2:51 pm
Re: Ultimate GPS Logger Shield – Confusion about correct fix
The code that parses the NMEA sentences is in the Adafruit_GPS library: https://github.com/adafruit/Adafruit-GP ... it_GPS.cpp
In this case, the fix quality is read from the $GPGGA sentence. The parsed output follows the NMEA sentence itself though, so the one that gave you the 'quality: 0' output would be the one above the text that you posted.
The GPS modules are capable of doing DGPS and SBAS. The commands to enable/disable them are:
and are explained in the GPS module's command datasheet:
http://www.adafruit.com/datasheets/PMTK ... 39-A01.pdf
In this case, the fix quality is read from the $GPGGA sentence. The parsed output follows the NMEA sentence itself though, so the one that gave you the 'quality: 0' output would be the one above the text that you posted.
The GPS modules are capable of doing DGPS and SBAS. The commands to enable/disable them are:
Code: Select all
set DGPS mode: $PMTK301,1*2D
disable DGPS mode: $PMTK301,0*2C
set SBAS mode: $PMTK319,1*24
enable SBAS: $PMTK313,1*2E
disable SBAS: $PMTK313,0*2F
http://www.adafruit.com/datasheets/PMTK ... 39-A01.pdf
Please be positive and constructive with your questions and comments.