Time Series Scalar VPS Cast Data Product
Device-level scalar data products for each cast of the VPS are described here.
Revision History
- 20120530: Initial Release
Formats
This data is available as PNG plots and MAT file data.
Description
VPS Cast data products produce one file or plot for each cast of the Vertical Profiler System (VPS). A cast is defined as a single pass through the water column. Possible values include 'Up', 'Down', 'Up - In Progress', 'Down - In Progress'. The VPS may pause at various levels throughout the water column to acquire data; this behaviour does not interrupt a cast. Only entire casts will be reported, except in the case of a cast that is ongoing in real-time, i.e. an 'In Progress' cast. The up and down casts are kept separate because certain instruments will perform better on either. For instance, the CTD will sample undisturbed water on a down cast as its intake is near the bottom of the of VPS. Please consult individual instruments' documentation for more information.
For each cast, a separate PNG plot or MAT data file will be produced. A generic VPS Cast plot will be a MATLAB subplot-type of plot, with a single plot for each sensor on the selected device. Each plot will have Pressure (decibars) on the Y-axis and the sensor on the X-axis. This pressure is actually the relative or gauge pressure measured by the CTD onboard the VPS relative to 0 decibars at sea level. Relative pressure is a convention used by oceanographers so that the pressure shown approximates the water depth. To accurately measure the water depth, the water density needs to be integrated throughout the water column - such a calculation is beyond the scope of this data product. The plot will note the start and end times of the cast in the title bar. Specialized overlay plots may be available in the future for specific devices such as the CTD. The MAT-file will contain the same data as the plot. To determine the start and end times of the cast from the MAT file, access a data structure and look at the time field, i.e. data(1,1).time(1) will be the start time, data(1,1).time(end) will be the end time of the cast. The file-name for either format will contain a device code followed by the start time of the data contained within and then a dash to indicate ancillary information. The ancillary information will contain the direction and start and end times of the cast, for instance: BarkleyCanyon-VPSUpperSlope_CTD_20120611T192844Z-VPS_Cast_Down_from20120611T192843Z_to20120611T202056Z.png. There may be multiple files produced for a single cast in the following scenarios: a cast crosses midnight (normally only applies to non-scalar devices), data interruption, device or site change or meta data change, or if the files created would be very large. The last scenario is by far the most common case for multiple files in a cast.
This data product is very similar to the 'Time Series Scalar Data' product, see http://wiki.neptunecanada.ca/display/DP/1. One of the differences is that VPS Cast data is only available on a device level basis, not as individual sensors. Unlike ordinary time series scalar data, time is not plotted in the .png plots, but it it integral to making the plots. Time is included in the MAT file data products. The MAT files are identical to the ordinary time series scalar data except that new files are made for every cast.
Discussion
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