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# ncl_ngritd - Man Page

Given the coordinates of a point, this routine performs a rotation of that point about a specified axis by a specified angle.

## Synopsis

CALL NGRITD (IAXS,ANGL,UCRD,VCRD,WCRD)

## C-Binding Synopsis

#include <ncarg/ncargC.h>

void c_ngritd(int iaxs, float angl, float *ucrd, float *ycrd,
float *wcrd)

## Description

IAXS

(an input expression of type INTEGER) specifies the axis about which rotation is to be done (1 for the U axis, 2 for the V axis, and 3 for the W axis).

ANGL

(an input expression of type REAL) specifies the magnitude, in degrees, of the rotation angle.

UCRD

(an input/output variable of type REAL) specifies the U coordinate of the point being rotated.

VCRD

(an input/output variable of type REAL) specifies the V coordinate of the point being rotated.

WCRD

(an input/output variable of type REAL) specifies the W coordinate of the point being rotated.

## C-Binding Description

The C binding argument descriptions are the same as the FORTRAN argument descriptions.

## Usage

This routine is used by NGGCOG and NGGSOG to effect the rotations that are used to generate an object of a specified shape at a specified point on the surface of the globe.

NGRITD assumes that the UVW coordinate system is right-handed.  Positive values of ANGL give counter-clockwise rotations and negative values of ANGL give clockwise rotations.  (When IAXS = 1, ANGL = 90 carries the positive V axis into the positive W axis; when IAXS = 2, ANGL = 90 carries the positive W axis into the positive U axis; when IAXS = 3, ANGL = 90 carries the positive U axis into the positive V axis.)

## Examples

Use the ncargex command to see the following relevant example:  cpex10.

## Access

To use NGRITD or c_ngritd, load the NCAR Graphics libraries ncarg, ncarg_gks, and ncarg_c, preferably in that order.

None.