Manual

June 2004 Isis® Sonar User's Manual, Volume 2 2
Many other values are controlled by strings received over RS-232 serial
interfaces from the navigation system and/or any serial device. Refer to Appendix
E of the Q-MIPS User’s Manual or
‘Serial Interfaces’ (Appendix D) of this
manual for descriptions of the values that can be set in this manner. Navigation
telemetry values are replicated in their respective fields from ping to ping until a
new navigation string is received at the serial port. Then the values present in the
string are used to update the appropriate fields in the footer. If desired, the
Q-MIPS or Isis system time can be synchronized to the time indicated in the
telemetry string.
All binary data are stored according to the Intel representation scheme. This is an
important distinction if you plan to read or write Q-MIPS-style data using
Motorola-based, MIPS-based, or SPARC-based platforms.
A.3 Imagery Data
Regardless of how many samples are collected per channel per ping, the data
are decimated (or replicated) to be stored at 1024 pixels per channel per ping by
Q-MIPS or the user-specified number of pings by Isis. For a discussion of
available decimation methods, refer to the description of the
ch1_sampleScheme field under the heading Channel 1 Sonar Parameters in
Table A-6 on page 16.
Isis can save both 8-bit and 16-bit data in Q-MIPS format.
A.3.1 Eight-Bit Data
Each sample is an unsigned 8-bit value with a range of 0-255. Assuming
that the DSP card in Isis still has a factory jumper-setting configuration, the
input range is 5 volts. During the conversion from 16-bit to 8-bit, the sign bit
is omitted. So 0-255 represents a voltage range of 0 5 volts or 0 -5 volts
depending on the original input signal. Note that for side-scan, the important
quality to log is the
magnitude of the signal from zero, not the actual
signed voltage.
A.3.2 Sixteen-Bit Data
The A/D converter on the Isis DSP card samples at 18 bits, with the 16 most
significant bits being available for storage. With 16 bits being saved, the
entire sample is logged. Each sample is a signed value.
Appendix A: Q-MIPS File Format