Read Sep90

The Read Sep90 module reads a SEPlib90 data set into AVS using SEPlib90 data access routines. It also allows the selection of a sub-set by specifying windowing parameters, so the whole data set doesn't have to be loaded when memory is an issue. Figure 1 shows the AVS user interface for the Read Sep90 module. It takes as input a SEPlib90 dataset and produces three outputs to downstream modules: a Header Values structure, a Data Values 2-D Field and a Grid Values n-D Field. The Header values structure below is a memory representation of both SEP90 header keys and Header Values File:

/******************************************************
       Keys Object
*******************************************************/
typedef struct KEY {
	char	name[MAXLABEL];	/* Name of Header Key */
	int	type;		/* Type of Header Key	*/ 
	int	pos;		/* Header Key Position in Header Record */
	} KEY_o;
/******************************************************
       Header Object
*******************************************************/
typedef struct HEADER {
	int	n_keys;		/* Number of Header Keys */
	KEY_o	*keys;		/* Vector of lenght n_keys containig key
          objects	*/
	int	n_records;	/* Number of Header Records */
	int	record_size;	/* Number of bytes in Header Records */
	char	*values;	/* Vector containing Records Values	*/
	}  HEADER_o;

The Data Values 2-D Field is a memory representation of the SEPlib90 Data Values File. The SEPlib90 data types supported are: scalar_byte, scalar_int, scalar_int, scalar_float, vec3_byte and vec3_float. The corresponding AVS output types are: scalars char, short, int, float, and 3-vector char and float. The third output, Grid Values, provides information about the superimposed, regular grid. The The Grid Values file is a n-D, scalar AVSfield_int, where each value represents is equal to the index of the corresponding trace and header in the Data Values Field and Header Values structure or -1 if there is no trace at that gridding location.

 

ReadSep90 Figure 1 Control panel for the Read Sep90 module.

A file browser widget is used to select the name of the History file associated with the input data set. The min and max type-in widgets allow the specification of minimum and maximum values for each axis. Axis 1 refers to time axis, and Axis 2 to Axis n refer to the Gridding coordinate system axes. The j widgets allow the user to specify an under-sampling rate along each Gridding coordinate system axis. Once the user has finished with the parameter specification, the Send Data one-shot widget should be selected to read the SEPlib90 data set and pass the output information to downstream modules.