Manual revision 017
Appendix I: NMEA Navigation Device Message and Data Formats
SBE 33
47
Data Formats
Position Data
Seven bytes of NMEA position data are appended to each scan of hex data
from the instrument.
Our software calculates latitude and longitude as follows:
Latitude (deg) = (byte 1 * 65536 + byte 2 * 256 + byte 3) / 50000
Longitude (deg) = (byte 4 * 65536 + byte 5 * 256 + byte 6) / 50000
Notes:
1.
If bit 1 in byte 7 is 1, this is a new position.
2.
If bit 8 in byte 7 is 1, Latitude is negative.
3.
If bit 7 in byte 7 is 1, Longitude is negative.
4.
North latitudes are positive, south latitudes are negative.
5.
East longitudes are positive, west longitudes are negative.
Example:
Appended position data = 2455FC5D32B141
byte 1 = 24 hex = 36 decimal
byte 2 = 55 hex = 85 decimal
byte 3 = FC hex = 252 decimal
byte 4 = 5D hex = 93 decimal
byte 5 = 32 hex = 50 decimal
byte 6 = B1 hex = 177 decimal
byte 7 = 41 hex = 01000001 binary
This is a new position (bit 1 in byte 7 is 1).
Latitude is positive (bit 8 in byte 7 is 0).
Longitude is negative (bit 7 in byte 7 is 1).
Latitude = (36 * 65536 + 85 * 256 + 252) / 50000 = 47.62616 degrees
Longitude = (93 * 65536 + 50 * 256 + 177) / 50000 = -122.1565 degrees
Depth Data (if applicable)
Three bytes of depth data are appended to each scan of data, after the
position data.
Our software calculates depth as follows:
Depth (meters) = (byte 1 * 65536 + byte 2 * 256 + byte 3) / 10
Example:
Appended depth data = 0032FC
byte 1 = 00 hex = 0 decimal
byte 2 = 32 hex = 50 decimal
byte 3 = FC hex = 252 decimal
Depth = (0 * 65536 + 50 * 256 + 252) / 10 = 1305.2 meters
Note:
If a Surface PAR sensor is also
connected to the SBE 33, the
Surface PAR data (three bytes) is
appended
before
the position data.
