Interface Specification Document
6.3.9
Sidescan Imagery Packets
When the sidescan option is present in the sonar and enabled, the sonar will output a left and
right sidescan packet for each sonar ping. The sidescan data will be generated using the same
ping as the bathymetry so it will be possible for the data collection system or subsequent process-
ing to use the bathymetry data to geographically register the imagery. Since the sidescan data
will be output by the sonar on ethernet and this type of output has a limitation of 1500 bytes or
less, the ping data from each beam may be broken up into multiple packets. The information for
the two beams will be output as a series of amplitude values, starting from the outermost sample
cell on the port side, through the center to the outermost sample cell on the starboard side. The
network transport protocol used is UDP/IP.
The number of amplitude values output for each packet will vary with range. If RMS or average
modes are used the data will be compressed to a maximum of 1024 samples per channel.
The data from the sonar will not be slant range corrected. Determining the altitude of the sonar
head and performing slant range correction will be the responsibility of the data acquisition sys-
tem.
The sonar imagery data will not be compensated for changes in sonar power and gain.
6.3.9.1 Sidescan
Packet
struct SIDESCAN_IMAGE
{
char
STX;
//
start
character
(0x02)
char
id;
//
packet
id
(0x48)
unsigned short
packet_size;
// size of packet - next field through last Amplitude value
unsigned
long
ping_no;
//
sequential
ping
number since sonar power-up / reset
DATA_TIME
data_time;
// time of ping for data packet
unsigned short
total_samples;
// total number of amplitude samples for ping
unsigned
short
ping_packet;
//
sequence number - (0 to n )
unsigned short
velocity;
// programmed sound velocity (LSB = 1 m/sec)
unsigned short
sample_rate;
// A/D sample rate (samples per second)
unsigned short
ping_rate;
// Ping rate (pings per second * 1000)
unsigned short
range_set;
// range setting for SeaBat (meters)
unsigned short
power;
// power setting for SeaBat
unsigned short
gain;
// gain setting for SeaBat
// bits
0-6 -
gain (1 - 45)
// bit
14
(0 = fixed, 1 = tvg)
// bit
15
(0 = manual, 1 = auto)
unsigned char
pulse_width;
// transmit pulse width (microseconds)
unsigned
char
tvg_spread;
//
spreading coefficient for tvg * 4
// valid values = 0 to 240 (0.0 to 60.0 in 0.25 steps)
unsigned
char
tvg_absorp;
//
absorption coefficient for tvg
unsigned char
flags;
// bit 0 - Roll stabilization flag. 0 = off, 1 = on.
unsigned
short
spare1[2];
//
more
spares
short
projector;
// projector setting
unsigned short
sample_count;
// number of amplitude samples in packet
unsigned short
amplitude[n];
// amplitude data where n = sample_count
// 12 bit amplitude stored in 12 most significant bits
unsigned char
spare2;
// spare to align ETX & checksum
char
ETX;
// packet end character (0x03)
unsigned short
checksum;
// checksum for data packet
};
______________________________________________________________________
SeaBat 8101 Operator's Manual
6-32
(ISD Rev 1.23) Version 3.02
