DCL:GRPH1:STPACK: Transformation Functions:Explanation of Subroutines: Coordinate Transformation (Subroutines)
Performs a normalization transformation (transformation of UC and VC) or map projection (transformation of TC and VC).
CALL STFTRN(UX,UY,VX,VY)
CALL STITRN(VX,VY,UX,UY)
CALL STSTRN(ITR,CXA,CYA,VX0,VY0)
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
- (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
.