This package defines the interactions between gridded spatial data and trace time series.
The TRACE_TERM struct stores a tracegeom (trace header data structure) set up to set up to sample a specific field (local gridded data). Both local and global grids are attributes of an IMODEL; the necessary data is extracted in the traceterm_init function and used to construct the captive tracegeom. Data is either inserted in grid (load=1) or extracted from grid (load=0), via call to sampletraces. The traceterm_init function also permits the user to offset all source and receiver coordinates by a fixed vector, which is useful in defining towed streamer sources.
SAMPLER is a shallow wrapper around TRACE_TERM. Besides an internal TRACE_TERM, SAMPLER also stores an array (IPNT) of field indices, The run method cycles through the fields indexed by the elements of this array. This feature is essential in defining source behaviour (load option) for systems such as global PML which duplicate dynamical fields in the physical domain. For such systems, source updates must be made to all copies of the relevant fields. For receiver behaviour (non-load or save option), only the first (0) indexed field is sampled.
MOVIE defines a sequence of snapshots of dynamic fields. Choice of fields to sample, and mnemonic keys used to specify this choice, deferred to specific model packages, but a simple interface for this key definition is provided. Thus MODEL plays the role of an abstract base.
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