Unicont SPb Ltd    Technical Documentation ADPC-101 
  Page 16 
8.8.4. NMEA LOG fmt – format of output NMEA line with current speed 
value: 
Disabled - output of speed value is disabled 
VMVTG - $VMVTG,,,,,x.x,N,,*cs 
VMVBW - $VMVBW,x.x,,A,,,*cs (NMEA v 2.0) 
IIVTG - $IIVTG,,,,,x.x,N,,*cs 
IIVBW - $IIVBW,x.x,,A,,,*cs 
SIVHW - $SIVHW,x.x,T,,,x.x,N,,*cs (mixed format: speed and heading 
value in one NMEA line) 
VMVBW - $VMVBW,x.x,,A,,,A,,V,,V*cs (NMEA v 2.3) 
------------------------------ 
cs – checksum. 
8.9  Non-authenticity of data 
1. Non-authenticity of gyrocompass data. 
Non-authenticity is defined by absence of reference signal. 
 As far as stepper type gyrocompass is concerned – lack of required level; 
 As far as synchro type gyrocompass is concerned – lack of sine signal differentials, 
emergence of timing jitter (breaking of sector alteration priority) or presence of inadmissible 
states. 
2. Non-authenticity of log data. 
Non-authenticity is determined provided that measured speed is 100 knots and more. 
In case when gyrocompass and/or log data are not trustworthy, relevant NMEA line is 
stopped for transmission to serial port and display shows ‘?’ (question) – at the beginning of 
relevant line, if alarm option is setted, device is emitted sound 
When trustworthy data are displayed, data transmission is resumed.