Triton Isis - Manual (Page 13)

June 2004 Isis® Sonar User's Manual, Volume 2 3
16 bits represent -32768 to +32767. This corresponds to an input voltage
range of -5 to +5 volts. To convert a sample from the Q-MIPS file, use the
following formula:
volts = (sample / 32768) x 5
Equation A-1. Formula for converting a Q-MIPS sample to 16-bit format
Note that the actual range is actually -5 volts to +4.9998 volts.
Each pixel of imagery will require either one or two bytes of disk storage
depending on whether the data are saved at 8 or 16 bits per pixel. The
number of bits per pixel is specified for Q-MIPS in the QMIPS.DAT file and
for Isis using the Record Setup command.
Isis and Q-MIPS can store imagery in any combination of raw and corrected
for each of up to four analog channels. A corrected channel has had the
water column removed and has been slant-range corrected so that the
displayed waterfall record approximates a “map-view” of the data.
If both raw and corrected data are saved by Isis or Q-MIPS, 1024 raw pixels
are saved followed by 1024 corrected pixels for each channel. All specified
types for channel 1 (raw and/or corrected) are saved first. Then all types for
channel 2 and so on. The complete order for up to the Q-MIPS maximum of
eight imagery channels is shown below. Remember, when a channel is not
present or a data type (raw or corrected) is not to be saved, it is omitted.
That is, no padding is done. Fewer imagery channels results in fewer bytes
stored per ping.
Table A-1. Relationship in Q-MIPS of channel to data type to location
Channel Data Type Read or Write Location
CH1 RAW Write only Port
CH1 CORRECTED Write or Read Port
CH2 RAW Write only Starboard
CH2 CORRECTED Write or Read Starboard
CH3 RAW Write only Port or Subbottom
CH3 CORRECTED Write or Read Port or Subbottom
CH4 RAW Write only Starboard or Subbottom
Appendix A: Q-MIPS File Format