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MGH_LOCATE2

MGH_LOCATE2

Name


  MGH_LOCATE2

Purpose


  This function calculates positions in the "index space" of a 2D
  curvilinear grid.

Calling Sequence


  Result = MGH_LOCATE2(xin, yin)

Positional Parameters


  xin, yin (input, 2-D numeric arrays)
    X & Y positions of the vertices of the curvilinear input grid.

Keyword Parameters


  To define the output locations, this function accepts the
  following keywords and passes them to GRIDDATA: DELTA, DIMENSION,
  GRID, START, XOUT, YOUT.

Return Value


  The function returns a floating array representing the output
  locations as fractional indices on the grid represented by the XIN
  & YIN arrays. The result is dimensioned [2,m] or [2,m,n] where [m]
  or [m,n] are the dimensions of the output locations.

Procedure


  Construct variables representing position in i direction and
  position in j direction and interpolate with GRIDDATA function
  PERFORMANCE
  I have tested this function using a [439,439] moderately curved
  input grid (NZ region SST--see MGH_EXAMPLE_LOCATE2). For large
  output grids (20000 vertices or more) time taken increases linearly
  @ 16,000 per second on a Pentium 4 2.67 GHz. For smaller output grids
  time is sub-linear.
  See also MGH_LOCATE2A which has essentially the same functionality
  but is faster on small output grids.
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  This software is provided subject to the following conditions:
  1. NIWA makes no representations or warranties regarding the
    accuracy of the software, the use to which the software may
    be put or the results to be obtained from the use of the
    software. Accordingly NIWA accepts no liability for any loss
    or damage (whether direct of indirect) incurred by any person
    through the use of or reliance on the software.
  2. NIWA is to be acknowledged as the original author of the
    software where the software is used or presented in any form.
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Modification History


  Mark Hadfield, 2002-07:
    Written.



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