New and very Intriguing NMEA Problem found

Hi,

Last sunday I have made a test with my GpsMap 276C in my boat, using
Laptop and the Hyperterminal program. My Map 276C was taking 12
satellites and running normal, and I have get exactly the same
results another user had get with a 172C. My position here (Salvador-
Bahia-Brazil) is S 12 48 W038 27 and thus GMT ¡V 3.

The test showed that:
a)The 276C was sending NMEA messages normally until 20:59:59 LCL
(23:59:59 GMT) after that, it begin to send invalid NMEA messages,
and little time after, stopped sending anything, see below a small
sample:

$GPRMC,235959,A,1248.705,S,03827.579,W,0.0,192.2,180207,23.0,W,A*3A
$GPRMB,A,0.04,L,AIC,BA01,1248.413,S,03827.698,W,0.315,338.3,,V,A*3B
$GPGGA,235959,1248.705,S,03827.579,W,1,12,0.8,4.2,M,-10.5,M,,*60
$GPGLL,1248.705,S,03827.579,W,235959,A,A*41
$GPBOD,345.6,T,8.6,M,BA01,AIC*04
$GPBWC,235959,1248.413,S,03827.698,W,338.3,T,1.4,M,0.315,N,BA01,A*6B
$GPVTG,192.2,T,215.2,M,0.0,N,0.0,K,A*2F
$GPXTE,A,A,0.04,L,N,A*07
$GPAPB,A,A,0.04,L,N,V,V,8.6,M,BA01,1.4,M,1.4,M,A*5E
<<<<<<<<<<<<<<<<<<<,,º================ 23:59:59 GMT
$GPRMC,000002,V,,,,,,,,,,N*51
$GPRMB,V,,,,,,,,,,,,,N*52
$GPRMC,000006,V,,,,,,,,,,N*55
$GPRMB,V,,,,,,,,,,,,,N*52
$GPRMC,000010,V,,,,,,,,,,N*52
$GPRMB,V,,,,,,,,,,,,,N*52
$GPRMC,000014,V,,,,,,,,,,N*56
$GPRMB,V,,,,,,,,,,,,,N*52
$GPRMC,000018,V,,,,,,,,,,N*5A
$GPRMB,V,,,,,,,,,,,,,N*52

b)Around 21:08:33 LCL (00:08:33 GMT) the 276C started to send NMEA
messages normally, see the sample below.

$GPRMC,000134,V,,,,,,,,,,N*55
$GPRMB,V,,,,,,,,,,,,,N*52
$GPRMC,000138,V,,,,,,,,,,N*59
$GPRMB,V,,,,,,,,,,,,,N*52
$GPRMC,000142,V,,,,,,,,,,N*54
$GPRMB,V,,,,,,,,,,,,,N*52
$GPRMC,000146,V,,,,,,,,,,N*50
$GPRMB,V,,,,,,,,,,,,,N*52
$GPRMC,000150,V,,,,,,,,,,N*57
$GPRMB,V,,,,,,,,,,,,,N*52
$GPRMC,000154,V,,,,,,,,,,N*53
$GPRMB,V,,,,,,,,,,,,,N*52
$GPRMC,000158,V,,,,,,,,,,N*5F
$GPRMB,V,,,,,,,,,,,,,N*52
<<<<<<<<<<<<<<<<<<,,º============== 00:08:33 GMT
$GPRMC,000833,A,1248.705,S,03827.579,W,0.0,192.2,190207,23.0,W,A*32
$GPRMB,A,0.04,L,AIC,BA01,1248.413,S,03827.698,W,0.315,338.3,,V,A*3B
$GPGGA,000833,1248.705,S,03827.579,W,1,12,0.8,4.8,M,-10.5,M,,*63
$GPGLL,1248.705,S,03827.579,W,000833,A,A*48
$GPBOD,345.6,T,8.6,M,BA01,AIC*04
$GPBWC,000833,1248.413,S,03827.698,W,338.3,T,1.4,M,0.315,N,BA01,A*62
$GPVTG,192.2,T,215.2,M,0.0,N,0.0,K,A*2F
$GPXTE,A,A,0.04,L,N,A*07
$GPAPB,A,A,0.04,L,N,V,V,8.6,M,BA01,1.4,M,1.4,M,A*5E



Conclusions:

1)The problem happens Every Day at that time on every place around
the world.
2)It is comproved in garmins 172C and 276C. What other models have
this problem?
3)As the 172C last update was in May/2006 and the last update
(software version 4.8) of my 276C was in Jan/2007, much more recent,
the suspicion of a widespread problem is very probable.
4)The time of day of the problem 23:59:59-00:08:33 is documented;
could be that there is another times when the error appears?
5)I will send warning messages by e-mail to all people I know that
sail using gps and autopilot.
6)I will open a new problem report with Garmin, regarding my 276C. I
suggest that other people using these and other models of Garmin gps,
do the test and open a problem with Garmin.
7)I repute this problem as a very high risk issue as almost all
sailors here have Garmin Gps units interfaced with Raymarine
Autopilots and we use extensively this interface, specially when
sailing tricky routes, in narrow channels, in bad weather or at
night.


Pascal Goncalves
S 13 00/W 038 27

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