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DCL:GRPH1:STPACK: Transformation Functions:Explanation of Subroutines: Coordinate Transformation (Subroutines)

6.4.1 stftrn/stitrn/ststrn

1.

Function

Performs a normalization transformation (transformation of UC and VC) or map projection (transformation of TC and VC).

2.

Call

vx, vy = NumRu::DCL.stftrn(ux,uy)
ux, uy = NumRu::DCL.stitrn(vx,vy)
NumRu::DCL.ststrn(itr,cxa,cya,vxoff,vyoff)

3.

Explanation of Arguments

ux,uy	(R)	The coordinates of UC/TC
vx,vy	(R)	The coordinates of VC.
itr	(I)	Transformation function number
cxa,cya	(R)	Factor to multiply coordinate value by
vx0,vy0	(R)	The position of the origin in VC

4.

Notes

(a)

In a map projection, if transformation is impossible due to factors such as singular points, the value of the internal variable rundef managed by glpget/glpset is returned. (The initial value is -999.0.)

(b)

This function performs the following operations.

• Performs a basic transformation on (UX,UY)  to (XX,YY) according to the transformation function number
• Furthermore, it expands or shifts by 

  vx = cxa*xx + vx0
  vy = cya*xx + vy0
  .