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Re: New GPS units additional NMEA prefixes
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If you are really interested, you can read the NMEA 0183 documnetation.? I used The short answer is that the TT3 and TT4 devices look at 2 NMEA 0183 sentences to sent position reports: 123519 Fix taken at 12:35:19 UTC 4807.038,N Latitude 48 deg 07.038' N 01131.000,E Longitude 11 deg 31.000' E 1 Fix quality: 0 = invalid 1 = GPS fix (SPS) 2 = DGPS fix 3 = PPS fix 4 = Real Time Kinematic 5 = Float RTK 6 = estimated (dead reckoning) (2.3 feature) 7 = Manual input mode 8 = Simulation mode 08 Number of satellites being tracked 0.9 Horizontal dilution of position 545.4,M Altitude, Meters, above mean sea level 46.9,M Height of geoid (mean sea level) above WGS84 ellipsoid (empty field) time in seconds since last DGPS update (empty field) DGPS station ID number *47 the checksum data, always begins with * RMC Recommended Minimum sentence C 123519 Fix taken at 12:35:19 UTC A Status A=active or V=Void. 4807.038,N Latitude 48 deg 07.038' N 01131.000,E Longitude 11 deg 31.000' E 022.4 Speed over the ground in knots 084.4 Track angle in degrees True 230394 Date - 23rd of March 1994 003.1,W Magnetic Variation *6A The checksum data, always begins with * The standard provides that each message be prefixed (talker ID) with $G? where the ? indicates where the data originalted: GP-GPS GL-GLONASS GN-Combined receiver GA-Galileo GB-BeDou So if the message $GPRMC would be a recommended Minimum sentence C from GPS satellites $GLRMC would be a recommended Minimum sentence C from GLONASS satellites $GNRMC would be a recommended Minimum sentence C from combination of satellites Same with GGA.? So you see that by ignoring the prefix, and just looking at the 3-character message ID and following Data, the tracker would send the proper data.? At least for $GP, $GL, and $GN, but I don't see why the others would be ignored. At least that is what I have been reading on the NMEA standard, again mainly: . KB8RCO On Thursday, May 7, 2020, 05:53:29 PM EDT, weatherspotting <weather@...> wrote: So who wants to explain all this to me? No clue what GL, GN, GA GB and why we would need different settings for GPS. David On 5/7/2020 11:47 AM, Rob Giuliano via groups.io wrote: Yes. Seems more and more GPS units are including GLONASS. Many include others. The prefix I gave correspond to: GP-GPS GL-GLONASS GN-Combined receiver GA-Galileo GB-BeDou From what I have looked at, many current GPS units are now using GN - Combined receiver It appears the messages are the same, just the second letter changes - at least for GN vs GP with respect to GGA and RMC. These come out as GNGGA and GNRMC insterad ofg GPGGA and GPRMC. I assume the GN means it could be calculated from either GLONASS or GPS satellites, or both. Robert Giuliano KB8RCO On Thursday, May 7, 2020, 12:20:03 PM EDT, vhsproducts via groups.io <vhsproducts@...> wrote: Robert, Is this a dual-band (NMEA+GLONASS) GPS receiver? 73, Allen AF6OF -----Original Message----- From: Rob Giuliano via groups.io <kb8rco@...>
To: [email protected] Sent: Thu, May 7, 2020 7:53 am Subject: [TinyTrak] New GPS units additional NMEA prefixes I just pulled my MTT4B out again and connected it to a new uBlox M8N GPS module. ? Settings: 10Hz update with output at 19200,n,8,1 I see the GPS sentences in a terminal, but the Green LED never flashes or comes on solid. I plugged in my older GPS, and everything is fine. ? Settings: 10Hz update with output at 19200,n,8,1 Then I realized the NMEA sentences all started with 'GN' instead of 'GP'.? Digging deeper, I found that uBlox configuration (u-center) allows you to change the "main talker" to 1-GPS (default is 3-Combined).? Don't forget to go to the CFG option to permanently set this value, or it will reset on power up.? Only difference appears to be the second letter.? Any chance of a future firmware update to handle more options? Current prefixes are: GP, GL, GN, GA, and GB. Robert Giuliano KB8RCO |
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