Black Sea Volumetric Rendering
6.837 Computer Graphics   Bill Wallis and Michael Dewberry

Processing the data

The data from Jason's passes over the wreck came in three different forms: the seafloor mesh, a matrix of 3D coordinates; the navigation data, a latitude/longitude/depth keyed by time; and the sub-bottom scan, density values also keyed by time. The first step was to correlate the PNS navigation data with the density readings. Synch.pl (read the source) was created to perform this step.

The PNS navigation looks like this: After a header string, a date/timestamp, and a description of the data, the X Y Z coordinates are listed line by line. PNS 99/06/11 15:43:00.09 EXA UTM JAS 000444.802 0004237.251 412.470 0.0 00 PNS 99/06/11 15:43:00.24 EXA UTM JAS 000444.800 0004237.254 412.470 0.0 00 PNS 99/06/11 15:43:00.35 EXA UTM JAS 000444.794 0004237.258 412.470 0.0 00 PNS 99/06/11 15:43:00.59 EXA UTM JAS 000444.786 0004237.261 412.470 0.0 00 PNS 99/06/11 15:43:00.84 EXA UTM JAS 000444.764 0004237.276 412.470 0.0 00

The sub-bottom profiler data is a timestamp followed by a long sequence of density values, sampled at 3000Hz. The density values don't have any particular unit type; they are an analog value dependent on the gain of the sonar unit, etc., and are mostly useful relative to each other. 99/06/11 15:46:03.24 SBX SBP 3000 51 2 3825 950 385 387 387 387 387 388 388 387 387 388 390 390 390 388 390 388 387 388 387 387 389 389 389 389 388 389 389 387 390 389 387 390 389 387 389 388 389 389 389 387 389 389 386 389 389 389 389 388 387 388 387 387 389 387 388 389 387 388 389 386 389 389 387 388 388 387 388 387 387 388 388 387 388 387 387 388 387 387 388 387 388 388 386 387 388 386 387 387 . . .

Synch.pl correlates the density readings with the X,Y,Z position in the PNS file and combines them into a synch file, which is used as the input to later programs. The X,Y,Z is followed by the density values. 56762.08 43.6149999999907 36.7779999999329 2.87 155 4064 950 385 387 387 387 387 388 388 387 387 . . . 56763.12 43.6139999999432 36.7700000000186 2.87 154 4092 1206 386 387 388 389 387 389 388 387 388 . . . 56763.37 43.5999999999767 36.7859999998473 2.87 154 4095 1462 385 387 386 387 387 387 388 388 388 . . .

and a log file StartTime: 56762.08 (15:46:02) Stop time: 58153.17 (16:09:13) MinPosition: 22.3919999999925 28.4769999999553 0.480000000000018 MaxPosition: 43.6149999999907 36.8050000001676 3.56999999999999 HSamples: 2507 VSamples: 700 MinV: 146 MaxV: 4095