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DCL:GRPH1:Summary:2-D Normalization Transformation

1.4.4 Settings of the U-Coordinate

Before drawing graphics in a U-coordinate, the SGFRM must be called and the parameters that determine the transformation functions must also be specified. The parameters that must be specified depends on the coordinate system, but the main parameters are all handled by SGpGET/SGpSET. However, SGpGET/SGpSET acts only as a bulletin board, and the values of the set parameters become effective when routine SGSTRF is called, which makes the transformation function effective. Since it is cumbersome to set the parameters for the transformation function individually, a routine is available for setting the parameters at once, and normally, this routine is used to set the parameters.

To set the parameters for a transformation function, the following coding is performed after SGFRM.

Rectangular Coordinate

       CALL SGSVPT(VXMIN, VXMAX, VYMIN, VYMAX)

       CALL SGSWND(UXMIN, UXMAX, UYMIN, UYMAX)

       CALL SGSTRN(ITR)

       CALL SGSTRF

Orthogonal Coordinate

       CALL SGSVPT(VXMIN, VXMAX, VYMIN, VYMAX)

       CALL SGSSIM(SIMFAC, XOFF, YOFF)

       CALL SGSTRN(ITR)

       CALL SGSTRF 

Map Projection Coordinate

       CALL SGSVPT(VXMIN, VXMAX, VYMIN, VYMAX)

       CALL SGSSIM(SIMFAC, XOFF, YOFF)

       CALL SGSMPL(PLX, PLY, PLROT)

       CALL SGSTRN(ITR)

       CALL SGSTRF

In conic projections, the latitude (STLAT1, STLAT2) of the standard parallel must be specified with SGRSET besides the above.

These parameters can be specified in any order as long as it is before the SGSTRF routine is called, which makes the transformation function effective. A Function is also available which returns the number of transformation function when inquired using the function name or abbreviation.