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ices-publications / SONAR-netCDF4

The SONAR-netCDF4 convention for sonar data
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Depth, range, transducer depth and heave #35

Open nilsolav opened 3 years ago

nilsolav commented 3 years ago

What would be the preferred way of coding range and/or depth in gridded data? I assume a range or deoth vector associated to the grid, but there are a few things to consider:

-For the first steps, keep the data as raw as possible, i.e. no regridding (which I think is needed when adjusting for heave?) -Support both range and depth for all steps, or tie the range and depth to a specific processing step? -How to store/use heave, transducer depth, range at first sample, sample interval? -Perhaps let the depth variable be adjusted to the actual depth (i.e. adjusting for heave, transducer depth, and range to first sample? -Let the range only be adjusted for range to first sample?

And probably several other things that I have not thought of.

Nils Olav

lberger29 commented 3 years ago

All the equations for converting beam coordinates to geographical coordinates are detailed in chapter 5 of the convention using parameters given in BeamGroup and every sample echo from BeamGroup can be located at a given depth. For GridGroup in step 3 the same equations will be used for calculating depth vector of the gridded data. For GridGroup in step 4 and 5 we do actually the way around we define a fix grid in depth referenced to the surface and we integrate all samples for each channel in each depth cells of the specified grid. The Depth vector is then fixed.