find_limit.F90 File Reference

Geo-reference utilities for a cubed-sphere grid. More...

Go to the source code of this file.

Functions/Subroutines
subroutine	find_limit (p1_in, p2_in, latmin, latmax)
	Given two points on a cubed-sphere grid, compute the maximum and minimum latitudinal extent of the resulting great circle. More...
subroutine	middle (p1, p2, p)
	Compute the latitude and longitude of the middle point between two given points. More...

Detailed Description

Geo-reference utilities for a cubed-sphere grid.

Author

Ning Wang

Definition in file find_limit.F90.

Function/Subroutine Documentation

find_limit()

subroutine find_limit	(	real*8, dimension(2), intent(in)	p1_in,
		real*8, dimension(2), intent(in)	p2_in,
		real*8, intent(out)	latmin,
		real*8, intent(out)	latmax
	)

Given two points on a cubed-sphere grid, compute the maximum and minimum latitudinal extent of the resulting great circle.

Parameters

[in]	p1_in	Latitude and longitude of point 1.
[in]	p2_in	Latitude and longitude of point 2.
[out]	latmin	Minimum latitudinal extent.
[out]	latmax	Maximum latitudinal extent.

Author

Ning Wang

Definition at line 16 of file find_limit.F90.

References middle().

Referenced by cal_lake_frac_depth().

middle()

subroutine middle	(	real*8, dimension(2), intent(in)	p1,
		real*8, dimension(2), intent(in)	p2,
		real*8, dimension(2), intent(out)	p
	)

Compute the latitude and longitude of the middle point between two given points.

There are two formulae available to compute it.

One derived from a more general m-sect formula:

  xyz = sin((1-f)*theta) / sin(theta) * xyz1 +
        sin(f*theta) /sin(theta) * xyz2 ;
  where theta is the angle of xyz1, and xyz2.
  

  xyz = 0.5 / sqrt[(1+dot(xyz1,xyz2))/2] * (xyz1+xyz2)
  

and the other one is the normalized middle point of the two end points:

  xyz = 0.5 * (xyz1+xyz2), xyz = xyz / sqrt(dot(xyz,xyz))
  

Parameters

[in]	p1	Latitude/longitude of first end point.
[in]	p2	Latitude/longitude of second end point
[out]	p	Latitude/longitude of the mid-point.

Author

Ning Wang

Date

March, 2006

Definition at line 80 of file find_limit.F90.

Referenced by find_limit().