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OSOceanAcoustics / echopype

Enabling interoperability and scalability in ocean sonar data analysis
https://echopype.readthedocs.io/
Apache License 2.0
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Sonar orientation and coordinate system convention, implementation #517

Open emiliom opened 2 years ago

emiliom commented 2 years ago

Investigate what platform or sonar/beam metadata attribute exists or should be added that clearly specifies the "direction" the echosounder is oriented (eg, downward vs upward looking). This need came about in the context of the OOI EK60/80 sensor @lsetiawan is using in his plotting tests, which is upward looking. This functionality would allow the echogram plots of raw data to be automatically oriented correctly with a depth y axis.

Looking through the SONAR-netCDF4 convention, the Sonar/Beam beam_mode attribute is helpful, but not fully what's needed; its values can be "vertical", "horizontal" and "inspection". Platform variables involving orientation and coordinate system may be usable, too, but currently the convention uses a ship-based frame of reference.

Follow up from @gavinmacaulay 👍 :

The upcoming version of SONAR-netCDF4 has a more complete orientation and coordinate system that allows for specifying absolute beam pointing directions - details here. It was designed for multi-beam bathymetric sonars and might be a bit complicated for just upward-looking echosounders, but was intended to be general enough for all purposes and does not assume a ship-based frame of reference (keep in mind that the platform is not necessary a vessel).

The beam_mode in version 1 of SONAR-netCDF4 is a label for the different groups of beams that fisheries omni-directional sonars have (e.g., a set of horizontal beams, a set of vertical beams, and spot beams - the word inspection comes from the usage in such sonars - a narrow beam for inspecting parts of a fish school)

emiliom commented 1 year ago

Refer to #1051 for related discussions.