ATLAS North America Proprietary
Sea Scan ARC Scout MKII Operations Manual
1 of 1
Page: 43
Issue: 1.2.4
SCTM2-OPS
Operations Manual
Name
Example
Units
Description
Sentence Terminator
<CR><LF>
Indicates end of sentence.
6.3.3
General NMEA 0183 Sentence Format
The NMEA 0183 format is a string based format that uses standard ASCII characters. The format follows this
format:
·
$aaccc,c—c*hh<CR><LF>
·
‘$’
signifies the start of the sentence
·
aaccc
are alpha numeric characters that identify the source of the string
·
‘,’
is the field delimiter
·
c—c
is the data or command sentence section. There can be one or more data fields that are
separated by the ‘,’ field delimiter character.
·
‘*’
signifies the end of the string and the beginning of the two checksum characters
·
hh
are the two checksum characters. These represent the checksum of the characters
between, but not including, the ‘$’ and ‘*’ characters. This is done by XOR’ing the 8 bits of each character.
The result is then broken up in the upper 4 bit nibble and lower 4 bit nibble and converted to the
equivalent alphanumeric hexadecimal value.
·
<CR> represents a decimal 10, hexadecimal 0D value (an ASCII Carriage Return character)
·
<LF> represents a decimal 13, hexadecimal 0A value (an ASCII Line Feed character)
For more information please see the National Marine Electronics Association 0183 standard.
7
SDS Data Output
The SDS (Sonar Data Stream) was created to be flexible and easy to use. The SDS can be "Streamed" over
and onto many different mediums. The Scout MkII primarily uses SDS over UDP/IP. This section describes
the Sonar Data Stream format and how it is transmitted over UDP/IP.
7.1
The Sonar Data Stream
All of the data output from the Scout MkII system is in the form of the Sonar Data Stream. The Sonar Data
Stream is a data format that allows the inclusion of sampled sonar data of various types, navigational and
positioning data, depth & altitude data, and orientation data all in the same data stream. The most
important concept to understand in the Sonar Data Stream is the time stamping system. Every piece of data
is stamped with a millisecond time stamp referenced to Greenwich Mean Time (or UTC). This allows the
data to be processed by other applications in accordance to the time at which the data was collected.
The Sonar Data Stream was engineered to be serialized and streamed into/out of a file, over network
connections of various types, and over asynchronous and synchronous serial links. It includes a
synchronization scheme that allows for a stream that is interrupted to resume receiving again at a known
good location in the data.
