1. .dat, 2. .meso and .meso.txt, and 3. .svpare recorded.
<dive number>.dat. The data files produced are self-documenting, i.e., there is a header on each file documenting the nature of data that it contains. At the beginning of the dive series, the system is configured as desired by the scientific party. The configuration defines packets of data, grouped by the recording period, in the order in which they appear in that record. The packets used were twos (2 second period), tens (10 second period), twom (2 minute period), and nav (period set by the navigation controller, usually 15 seconds, and consisting of NAV0 records with the ship ping transmitted on the minute and recorded at :15 seconds after the minute, and NAV1 records with the sub pings transmitted at :15, :30 and :45 seconds after the minutes and recorded at :30, :45, and on the next minute, respectively. The packet configuration for the Mixing Zephyr Program was (note change of configuration in twos packet beginning Dive 2932):
#Start_Header #name packet mode digits prec comments D_TIME twos cur 8 2 ALTITUDE twos cur 4 1 #Benthos instrument in tail DSALT_RANGE twos cur 7 1 #Datasonics instrument skids DEPTH_3 twos cur 6 1 #Paroscientific TEMP_LOW twos cur 3 1 TEMP_HIGH twos cur 4 1 HEADING twos cur 4 1 #gyro DEPTH_1 twos cur 6 0 PITCH twos cur 7 3 # + = bow up *2932- only ROLL twos cur 7 3 # + = starboard *2932- only D_TIME tens cur 8 2 # computed time DATE tens cur 6 0 DIVE tens cur 4 0 ALTITUDE tens cur 4 1 DSALT_RANGE tens cur 7 1 DEPTH_3 tens cur 6 1 HEADING tens cur 4 1 TEMP_WINDOW tens cur 3 1 DSALT_TEMP tens cur 7 1 TEMP_LOW tens cur 3 1 TEMP_HIGH tens cur 4 1 DEPTH_1 tens cur 6 0 D_TIME twom cur 8 2 # computed time DIVE twom cur 4 0 VB_PRES twom cur 5 1 VB_TEMP twom cur 3 1 HP_AIR_PRES twom cur 5 1 CAM_1_CNT twom cur 3 0 CAM_2_CNT twom cur 3 0 INTERR_FREQ twom cur 3 1 TRACK_FREQ twom cur 3 1 DEPTH_1 twom cur 6 0 SHIP_SUB nav cur 1 0 D_TIME nav cur 8 2 # computed time ALTITUDE nav cur 4 1 DSALT_RANGE nav cur 7 1 DEPTH_3 nav cur 5 1 HEADING nav cur 4 1 TEMP_WINDOW nav cur 3 1 INTERR_FREQ nav cur 3 1 TRACK_FREQ nav cur 3 1 LBL_0_FREQ nav cur 3 1 LBL_0_TIME nav cur 6 4 LBL_1_FREQ nav cur 3 1 LBL_1_TIME nav cur 6 4 LBL_2_FREQ nav cur 3 1 LBL_2_TIME nav cur 6 4 LBL_3_FREQ nav cur 3 1 LBL_3_TIME nav cur 6 4 X_POS nav cur 7 2 #computed from LBL0/LBL1 Y_POS nav cur 7 2 LAT_D nav cur 2 0 LAT_M nav cur 5 3 LON_D nav cur 3 0 LON_M nav cur 5 3 DEPTH_1 nav cur 6 0
<dive number>.meso. These data are in a binary format and a second ascii-encoded file is produced by the program mesoread at the time when the data are transferred from the sub to the shipboard data system with the filename
<dive number>.meso.txt. These records consist of a brief header with information on the origin of the file, followed by a series of blocks of data delimited by two header lines. After the two header lines in each block (which are self-documenting), there are a series of two-way travel times. A number of programs, developed by Dan Scheirer (email@example.com), are available to work with data in this form. These can be found in $ZEPHYR/mesoproc/.
During our program we recognized that the number of travel times recorded did not seem consistent with the information in the header. After e-mail discussion with Bill Chadwick (firstname.lastname@example.org) and Dan Scheirer, we set up to acquire raw data from the instrument with the following results. Scheirer made the observation that the problem may be in the assumption that the angle of the final ping of one sweep equals the starting angle of the next sweep. While the Mesotech manual was ambiguous on this point, we did find that the raw data coming on the serial line from the Mesotech to the data logger would have the answer, so Ken Feldman (email@example.com), the WHOI SSSG technician on board, set up to record that data directly. The records output, for a nominal 30 degree scan, were
L 0740 0 L 0736 0 R 0740 0 R 0744 0 28 records deleted R 0860 0 R 0864 0 L 0860 0The direction reported is the direction prior to the ping, the 4 digit number is the angle in units of .225 degree and 0 was the range (deck test). Thus the extreme left position was 165.6 degrees and the extreme right position was 194.4 degrees, a scan of 28.8 degrees which seems to be what Mesotech considers a nominal 30 degrees.
The ####.meso.txt records produced with mesoread for these same data contain the header when the transition occurs from L to R and report that angle as the start angle. Thus for these scans the start angles in the header were 166.5 and 193.5. The geometric pattern of the beams is thus:
LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRScheirer is working on modifications to his code (e-mail dated 6/8/95) to correct these problems.
<dive number>.svp. These containing three fields per record, the depth in meters, the sound velocity in meters per sec and the temperature in degrees Celsius. The last record has two fields with values of -1.