Output Datagrams; Introduction - Kongsberg EM - REV M Instruction Manual

Kongsberg EM Series

3 OUTPUT DATAGRAMS

3.1 Introduction

40
Topics
• Introduction on page 40
• Multibeam data on page 43
• External sensors on page 64
• Sound speed on page 75
• Multibeam parameters on page 78
• PU information and status on page 97
• SIS generated output on page 105
Output datagrams are usually logged to disk on the EM Series
Operator Station. The output datagrams may also be exported to
user provided programs on the Operator Station or on an external
Ethernet network using UDP protocol (remote logging). An
NMEA DPT depth datagram may be exported on a serial line.
The output datagrams are mostly in binary format using signed
or unsigned integer numbers with lengths of 1, 2 or 4 bytes.
With a PC based operator station little endian is normally used,
while big endian is used on Unix work stations. The same byte
order as used on the operator station is used for the output
datagrams.
Note
Please be aware that the use of big endian is not maintained on
the newer sounders (EM 3002, EM 710, EM 302 and EM 122),
since the operator station is PC based running Windows or Linux.
Note
We recommend that software written to decode EM Series data
includes a check for the byte ordering with a provision for byte
swapping. Suitable data fields to check on are the length field at
the start of the datagram, the EM Series model number field and
possibly the date and time fields.
The basic output datagram structure established with the EM
100 echo sounder is retained.
• All datagrams (except the NMEA DPT datagram) start with
STX, datagram type and time tag, and end with ETX and
checksum (sum of bytes between STX and ETX). In addition
the total length of the datagram (not including the length field)
will precede the STX byte, given as a four byte binary number.
850-160692/M