COVIS Plume Doppler Raw Data Files
This is a description of this raw DOPPLER mode data from COVIS.
Oceans 2.0 API filter:
- 20111123: Initial product released
The TAR.GZ files contain the raw data and the metadata needed to process and interpret in files of CSV, JSON and BIN formats. The following table lists the types of files and the information each contains. All of the JSON files are ascii text and human readable (with some effort). Similarly the CSV files can be read directly as ascii or loaded into a spreadsheet program like Excel. The BIN files are binary. Further details are supplied within the examples below.
Main metadata including timestamp, acquisition mode (“imaging”), and various sonar parameters (transmit pulse length, frequency, etc.). Some parameters can be set by direct interaction with the sonar and some are fixed.
This contains data from the attitude sensor (time, pitch, roll, heading). All measurements are in degrees. Pitch and Roll are gravity referenced. Heading is magnetic. There is one record per rotator stop.
This file contains data from the rotator motors (pitch, roll, yaw). All measurements are in degrees relative to an arbitrary reference. There is one record per rotator stop.
This file is derived from the above two files but contains one record per sonar ping. It lists the pings (numbering from 1 up) and gives the time (seconds, microseconds), rotator data (pitch, roll, yaw), and attitude data ( pitch, roll, heading) for each ping.
These are the metadata for each ping. Some of this information may overlap with sweep.json and some of it is set by the experimenter.
These are the actual data files ping-by-ping. They are in binary format. There should be one rec_7038_x.bin for every rec_7000_x.json.
Oceans 2.0 API filter: extension=tar
The examples are from APLUWCOVISMBSONAR001_20101001T121520.649Z-DOPPLER.tar.gz
attitude.csv – This the first three lines of a particular file.
- time is the minutes:seconds at which the data is measured.
- kPAngle is the pitch in degrees
- kR Angle is the roll in degrees
- kHeading is the magnetic direction (in degrees) the sonar is pointing
index.csv – This the first three lines of a particular file.
where the columns are
- Ping is the ping number. It always starts at 1.
- Pitch is from the same data as in rotator.csv
- Roll is from the same data as in rotator.csv
- Yaw is from the same data as in rotator.csv
- kPAngle is from the same data as in attitude.csv
- kRAngle is from the same data as in attitude.csv
- kHeading is from the same data as in attitude.csv
Note that the attitude and rotator data should be consistent but may disagree since they are independently measured.
where the columns are
- Time in minutes:seconds.deciseconds
- Pitch in degrees
- Roll in degrees
- Yaw in degrees
rec_7000_xxxxxx.json – Reson format for ascii metadata file documented in rec7000.pdf
rec_7038_xxxxxx.bin – Reson format for binary data documented in rec7008.pdf
The difference in the modes relates to the sonar setup, that is which receiver and transmitter are used or what pulse length is used. The table below listed the relevant parameters for each period of ongoing operation.
- The Doppler mode uses a larger pulse length and a higher ping count to increase averaging; the reliability of the eventual velocity estimates depends on the amount of averaging possible.
- The Imaging mode uses a shorter pulse length to increase the resolution of the resulting image. Resolving smaller details is more important here than increasing the averaging power, especially as the backscatter intensity estimates are fairly robust.
- The Diffuse mode differs in using the shortest pulse length (for high resolution of smaller features) and it is the only mode to use the 200 kHz transmitter.
Sweep count, start position, position increments, position steps, and settling time control the operation of the rotators. Ping count, ping rate, and delay control the overall collection of pings as well as how the pings are coordinated with the rotator motions. Two different source transducers are available (200 kHz and 400 KHz); different modes use different transmitters. The sonar range controls how long the sonar listens and records for each ping (sufficient time for two way travel over the specified range). The pulse width controls the resolution along the ping. Transmit power controls the energy put into the water with each ping. Reciever gain controls how much the received signal is amplified before digitizing. All the rest of the relevant parameters (like sampling rate for the digitization) are the same for all three modes. This information is collected in the sweep.json files, whether it varies between mode or not.
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