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APIRUS Use Cases

This document will serve to capture the use cases we want the API to cover.

The actual API to do this will get documented elsewhere.

The CF/CDM GRID object (we have been calling this "RGRID") is really just a specific type of SGRID object, so perhaps we only need to write code to deal with SGRID and UGRID?

We need tools that will work with a dataset object that can have SGRID or UGRID objects as children. We need to have ways of instantiating these objects, and methods that work with them.

Instantiation

  • Be able to create these objects from local netcdf files or remote opendap datasets (and eventually other services like CDMremote).
  • Ability to create these objects directly from code -- i.e. not dependent on a netcdf file existing. This opens the door to other arbitrary file format.
  • check for compliance with SGRID or UGRID and if valid, return the appropriate object.
  • allow the user to fix or supply missing information so that valid SGRID or UGRID objects can be created from invalid netcdf.
  • not load any coordinate data or data values

Core Uses

The core uses are about data extraction

  • Subsetting by bounding box in real coordinates (x, y) or (lon, lat) - This would produce a new *grid object, fully compliant, that contained all the cells that intersect with the specified bounds. - The user can specify a lat-lon-aligned bounding rectangle, or an arbitrary polygon in lat-lon coords. - whether it is lazy-tied to the original data source is an implementation detail..
  • Convert from curvilinear grid to ugrid: use can convert a curvilear grid to a ugrid, which can then be subset, etc. -- the reverse operation is not possible in the general case.
  • Vertical slices (transects) along arbitrary (x,y) paths, and also (x,y,t) paths.
  • Trajectories along arbitrary (x,y), (x,y,z) and (x,y,z,t) paths
  • Horizontal transects at specific z level, depth below surface, and height above bottom
  • velocity vectors rotated to north/east and averaged or interpolated to user-specified locations (e.g. node, face, edge)
  • extract timeseries profile using different interpolations schemes (nearest, linear) to a specified lon,lat location
  • extract timeseries using different interpolations schemes (nearest, linear in x,y space, spline in depth) to specified (lon,lat,z location)

Higher Level Analysis

This is analysis stuff -- beyond just accessing the data.

  • isosurfaces
  • total amount over specified region
  • vorticity