Report of Garmin GLO Firmware 2.70
Date and time format : "yyyy/mm/dd hh:mm:ss.s" UTC

Note) Since the accuracy of the location information is sufficient, no problem for applications such as walk navigation.
         It is not suitable for time correction purpose.
         When used for car navigation, it may pass the interchange if the timing is very bad.

Firmware 3.00 : No improvement.
Firmware 2.90 : No improvement.
Firmware 2.80 : No improvement.
1. NMEA sentence output does not reach to 10Hz.
   RMC sentence output period is about 8.3Hz.
   

2. It frequently outputs the identical Time and data in an identical Location.
   It occurs about once in average at 162 seconds.
   The data of the equivalence time are output in succession (they produce the space of approximately 0.2 seconds just before that).
Receive Timing:
ReceiveTime RMCtime   RMC sentence
22:23:34.693 22:23:34.6 $GPRMC,222334.6,A, ...
22:23:34.813 22:23:34.7 $GPRMC,222334.7,A, ...
22:23:34.999 22:23:34.9 $GPRMC,222334.9,A, ...
22:23:35.203 22:23:35.1 $GPRMC,222335.1,A, ...
22:23:35.208 22:23:35.1 $GPRMC,222335.1,A, ...
22:23:35.309 22:23:35.2 $GPRMC,222335.2,A, ...
22:23:35.428 22:23:35.3 $GPRMC,222335.3,A, ...
22:23:35.596 22:23:35.5 $GPRMC,222335.5,A, ...

NMEA sample (Moving at 89.5km/h):
$GPRMC,002508.1,A,3519.78759,N,13921.56864,E,048.39,078.1,191115,007.0,W,D*24
$GPGGA,002508.1,3519.78759,N,13921.56864,E,2,15,0.7,22.1,M,35.5,M,,*6B
$GPRMC,002508.2,A,3519.78786,N,13921.57025,E,048.32,078.4,191115,007.0,W,D*27
$GPGGA,002508.2,3519.78786,N,13921.57025,E,2,15,0.7,22.1,M,35.5,M,,*66
$GPRMC,002508.4,A,3519.78839,N,13921.57348,E,048.31,078.7,191115,007.0,W,D*22
$GPGGA,002508.4,3519.78839,N,13921.57348,E,2,15,0.7,22.2,M,35.5,M,,*60
$GPRMC,002508.4,A,3519.78839,N,13921.57348,E,048.31,078.7,191115,007.0,W,D*22
$GPGGA,002508.4,3519.78839,N,13921.57348,E,2,15,0.7,22.2,M,35.5,M,,*60
$GPRMC,002508.5,A,3519.78865,N,13921.57509,E,048.26,078.8,191115,007.0,W,D*20
$GPGGA,002508.5,3519.78865,N,13921.57509,E,2,15,0.7,22.2,M,35.5,M,,*6B
$GPRMC,002508.6,A,3519.78891,N,13921.57668,E,048.18,079.0,191115,007.0,W,D*28
$GPGGA,002508.6,3519.78891,N,13921.57668,E,2,15,0.7,22.2,M,35.5,M,,*67

Check of 2015/11/13 00:00:00.1 to 2015/11/15 23:59:59.5

3. Sometimes NMEA sentence is interrupted.
   1 or more seconds of interruption about four times per day, a maximum of about 15 seconds interrupted.
   It might be sending the old data at the restart, in this case the time is delayed (Only one cycle).
NMEA sample:
$GPRMC,040304.5,A,3520.14665,N,13924.42658,E,000.09,267.7,131115,007.0,W,A*29
$GPGGA,040304.5,3520.14665,N,13924.42658,E,1,15,0.6,17.5,M,35.5,M,,*6C
$GPRMC,040304.6,A,3520.14665,N,13924.42658,E,000.08,267.7,131115,007.0,W,A*2B
$GPGGA,040304.6,3520.14665,N,13924.42658,E,1,15,0.6,17.5,M,35.5,M,,*6F
--- 12.7 seconds elapsed ---
$GPRMC,040304.7,A,3520.14665,N,13924.42658,E,000.05,267.7,131115,007.0,W,A*27
$GPGGA,040304.7,3520.14665,N,13924.42658,E,1,15,0.6,17.5,M,35.5,M,,*6E
$GPRMC,040317.4,A,3520.14665,N,13924.42658,E,000.02,267.7,131115,007.0,W,A*21
$GPGGA,040317.4,3520.14665,N,13924.42658,E,1,14,0.6,17.5,M,35.5,M,,*6E
$GPRMC,040317.5,A,3520.14665,N,13924.42658,E,000.01,267.7,131115,007.0,W,A*23
$GPGGA,040317.5,3520.14665,N,13924.42658,E,1,14,0.6,17.5,M,35.5,M,,*6F
   
   
   

Screen shot (NMEA Monitor for windows):

4. Time advances 1 second only once a week for 17 seconds.
   From the TOW=0 of GPS-time to UTC=0:0:0 (17 seconds = leap second correction value = UTC - GPStime).
   It occurs just before midnight every Saturday in UTC.
   
Date and time of occurrence (UTC).
GPS week : Start_time(TOW=0) to End_time
1871 : 2015/11/14 23:59:43 to 2015/11/15 00:00:00
1872 : 2015/11/21 23:59:43 to 2015/11/22 00:00:00
...
2096 : 2020/03/07 23:59:42 to 2020/03/08 00:00:00
2097 : 2020/03/14 23:59:42 to 2020/03/15 00:00:00
2098 : 2020/03/21 23:59:42 to 2020/03/22 00:00:00
2099 : 2020/03/28 23:59:42 to 2020/03/29 00:00:00
2100 : 2020/04/04 23:59:42 to 2020/04/05 00:00:00
2101 : 2020/04/11 23:59:42 to 2020/04/12 00:00:00
2102 : 2020/04/18 23:59:42 to 2020/04/19 00:00:00
2103 : 2020/04/25 23:59:42 to 2020/04/26 00:00:00
2104 : 2020/05/02 23:59:42 to 2020/05/03 00:00:00
2105 : 2020/05/09 23:59:42 to 2020/05/10 00:00:00
2106 : 2020/05/16 23:59:42 to 2020/05/17 00:00:00
2107 : 2020/05/23 23:59:42 to 2020/05/24 00:00:00
2108 : 2020/05/30 23:59:42 to 2020/05/31 00:00:00
2109 : 2020/06/06 23:59:42 to 2020/06/07 00:00:00
2110 : 2020/06/13 23:59:42 to 2020/06/14 00:00:00
...
   Screen shot (NMEA Monitor for windows):
   

   Additional notes:
      Because there was a leap second insertion at 2017/1/1 0:00:00, it was 18 seconds from 23:59:42 to 0:00:00.


5. Sometimes time of 238 seconds delay will continue 750 seconds.
   Period that occurs about 20 days from 6 hours, Occurrence timing is unknown.
   
   Date and time of occurrence of confirmed:
    2015/11/13 07:38:37.0
    2015/11/16 13:13:37.0
    2015/11/24 22:58:37.0

   Screen shot (NMEA Monitor for windows):
   


6. GSA and GSV sentence is shared by GPS and GLONASS.
   1) Used satellites can not be confirmed only up to 12 satellites.
   2) GSV sentence is expanded to up to six sentences.
   3) SV number of GLONASS does not have a regularity.
NMEA sample of GLO:
$GPRMC,230655.9,A,3520.14407,N,13924.42820,E,000.03,344.7,241115,007.0,W,A*28
$GPGGA,230655.9,3520.14407,N,13924.42820,E,1,20,0.6,18.7,M,35.5,M,,*68
$GPVTG,344.7,T,351.8,M,000.03,N,0000.05,K,A*1E
$GPRMC,230656.0,A,3520.14407,N,13924.42820,E,000.06,344.7,241115,007.0,W,A*27
$GPGGA,230656.0,3520.14407,N,13924.42820,E,1,20,0.6,18.7,M,35.5,M,,*62
$GPVTG,344.7,T,351.8,M,000.06,N,0000.11,K,A*1E
$GPGSA,A,3,11,01,08,84,72,92,30,74,19,32,83,28,1.0,0.6,0.8*3E
$GPRMC,230656.2,A,3520.14407,N,13924.42820,E,000.05,344.7,241115,007.0,W,A*26
$GPGGA,230656.2,3520.14407,N,13924.42820,E,1,20,0.6,18.7,M,35.5,M,,*60
$GPVTG,344.7,T,351.8,M,000.05,N,0000.10,K,A*1C
$GPGSV,6,1,21,50,00,000,00,11,41,067,28,01,49,041,40,08,17,114,40*75
$GPGSV,6,2,21,84,39,067,29,72,08,214,25,92,43,052,31,30,03,224,25*75
$GPGSV,6,3,21,74,13,183,34,19,71,022,41,32,40,054,38,83,02,023,18*76
$GPGSV,6,4,21,28,61,265,39,80,15,321,22,89,12,303,27,93,53,139,37*76
$GPGSV,6,5,21,85,25,265,24,06,12,260,38,03,70,101,40,90,47,343,39*7A
$GPGSV,6,6,21,23,11,141,30*4C


NMEA sample of LEA-M8T (u-blox):
$GNRMC,230656.20,A,3520.14282,N,13924.42944,E,0.022,,241115,,,A*61
$GNVTG,,T,,M,0.022,N,0.041,K,A*38
$GNGNS,230656.20,3520.14282,N,13924.42944,E,AA,18,0.67,24.4,39.0,,*55
$GNGGA,230656.20,3520.14282,N,13924.42944,E,1,12,0.67,24.4,M,39.0,M,,*75
$GNGSA,A,3,01,08,19,32,03,28,06,17,23,11,,,1.18,0.67,0.98*1C
$GNGSA,A,3,71,76,65,77,88,87,72,86,,,,,1.18,0.67,0.98*14
$GPGSV,3,1,11,01,50,040,34,03,70,108,35,06,11,258,28,08,18,113,28*7C
$GPGSV,3,2,11,11,42,066,31,17,38,315,29,19,71,016,33,23,10,142,26*77
$GPGSV,3,3,11,28,61,268,37,30,04,225,22,32,41,056,29*42
$GLGSV,3,1,11,65,11,182,35,70,04,024,,71,44,056,30,72,50,142,32*6C
$GLGSV,3,2,11,76,09,215,31,77,26,267,24,78,15,322,,85,01,098,*6C
$GLGSV,3,3,11,86,40,065,33,87,46,339,37,88,10,300,29*55
$GNGLL,3520.14282,N,13924.42944,E,230656.20,A,A*7A
$GNGST,230656.20,23,,,,0.73,0.69,1.4*40
$GNZDA,230656.20,24,11,2015,00,00*7E


Skyplot by Trimble Planning

Comparison of GLONASS SV#
Planning  GLO  LEA-M8T
R017465
R026966
R037867
R047968
R058869
R068370
R079271
R089372
R097173
R106674
R117375
R127276
R138577
R148078
R158779
R168680
R177781
R187082
R197683
R207584
R219185
R228486
R239087
R248988

7. About NMEA sequence.
A current sequence : Peak = 9 Sentences / 0.1 Sec.
0.0S: RMC, GGA, VTG, GSA
0.1S: RMC, GGA, VTG, GSV1, GSV2, GSV3, GSV4, GSV5, GSV6
0.2S: RMC, GGA, VTG
0.3S: RMC, GGA, VTG
0.4S: RMC, GGA, VTG
0.5S: RMC, GGA, VTG
0.6S: RMC, GGA, VTG
0.7S: RMC, GGA, VTG
0.8S: RMC, GGA, VTG
0.9S: RMC, GGA, VTG

Improvement plan (disperse the GSV sentence) : Peak = 4 Sentences / 0.1 Sec.
0.0S: RMC, GGA, VTG, GSA
0.1S: RMC, GGA, VTG, GSV1
0.2S: RMC, GGA, VTG, GSV2
0.3S: RMC, GGA, VTG, GSV3
0.4S: RMC, GGA, VTG, GSV4
0.5S: RMC, GGA, VTG, GSV5
0.6S: RMC, GGA, VTG, GSV6
0.7S: RMC, GGA, VTG
0.8S: RMC, GGA, VTG
0.9S: RMC, GGA, VTG
8. Problem with Bluetooth simultaneous connection.
Connecting from multiple PCs at the same time may hang up in a few minutes.
It restores by turning on the power supply again.

Used utility:
   NMEA Monitor for windows
   RMC time check Utility
   NMEA to KMZ file converter (Used to CSV conversion from NMEA)
   RMC Delay Information Extraction Utility
   Trimble Planning
   GREP
   Microsoft Excel

Additional notes: Time error from 2016/8/9 to 2016/10/9.
   
   
2016/08/16 06:06:07.2 to 06:18:37.1 : Delay for 238 seconds continues for 750 seconds.
2016/08/20 23:13:37.2 to 23:26:07.2 : Delay for 238 seconds continues for 750 seconds.
2016/08/25 23:18:37.2 to 23:31:07.1 : Delay for 238 seconds continues for 750 seconds.
2016/08/26 05:02:37.4 to 05:08:37.3 : Gain for 13 seconds continues for 360 seconds.
2016/09/01 01:38:37.2 to 01:51:07.2 : Delay for 238 seconds continues for 750 seconds.
2016/09/08 07:41:07.2 to 07:53:37.3 : Delay for 238 seconds continues for 750 seconds.
2016/09/10 15:18:37.2 to 15:31:07.1 : Delay for 238 seconds continues for 750 seconds.
2016/09/18 06:36:07.0 to 06:48:37.2 : Delay for 238 seconds continues for 750 seconds.
2016/09/19 20:43:37.0 to 20:56:07.3 : Delay for 238 seconds continues for 750 seconds.
2016/09/23 00:08:37.0 to 00:21:07.3 : Delay for 238 seconds continues for 750 seconds.
2016/09/30 17:51:07.2 to 18:03:37.1 : Delay for 238 seconds continues for 750 seconds(9/30 18:03:04.6 delay for 254.6 seconds).
2016/10/01 23:51:07.2 to 00:08:37.3 : Delay for 238 seconds continues for 1050 seconds(10/01 23:59:43.0 to 10/02 00:03:58.0 : 237 seconds of delay is continuing 255 seconds).

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