;+
; @file_comments
;
; @categories
;
; @param NUM
;
; @param RECSTART
;
; @returns
;
; @restrictions
;
; @examples
;
; @history
;
; @version
; $Id$
;-
FUNCTION read_grib_gds, num, recstart
;
  compile_opt idl2, strictarrsubs
;
  offset = recstart+8
  a = assoc(num, bytarr(1, /nozero), offset-1)
  sizepds = bit2int([binary(a[1]), binary(a[2]), binary(a[3])])
;
  offset = recstart+8+sizepds
  a = assoc(num, bytarr(1, /nozero), offset-1)
;
  sizegds = bit2int([binary(a[1]), binary(a[2]), binary(a[3])])
;
  nv = (a[4])[0]
  pv = (a[5])[0]
;
  gridtype = (a[6])[0]
;
  CASE 1 OF
; Latitude/Longitude Grid
; Gaussian Latitude/Longitude Grid
    gridtype EQ 0 OR gridtype EQ 4:BEGIN
      ni = bit2int([binary(a[7]), binary(a[8])])
      nj = bit2int([binary(a[9]), binary(a[10])])
;
      la1 = bit2int([binary(a[11]), binary(a[12]), binary(a[13])], /checkneg)/1000.
      lo1 = bit2int([binary(a[14]), binary(a[15]), binary(a[16])], /checkneg)/1000.
;
      resflags = binary(a[17])
;
      la2 = bit2int([binary(a[18]), binary(a[19]), binary(a[20])], /checkneg)/1000.
      lo2 = bit2int([binary(a[21]), binary(a[22]), binary(a[23])], /checkneg)/1000.
;
      di = bit2int([binary(a[24]), binary(a[25])])/1000.
      IF di EQ 65.5350 THEN di = -1
;
      IF gridtype EQ 0 THEN BEGIN
        dj = bit2int([binary(a[26]), binary(a[27])])/1000.
        IF dj EQ 65.5350 THEN dj = -1
      ENDIF ELSE BEGIN
        n = bit2int([binary(a[26]), binary(a[27])])
      ENDELSE
;
      scanflags = binary(a[28])
;
      res = {size:sizegds, gridtype:gridtype, ni:ni, nj:nj, la1:la1, la2:la2, lo1:lo1, lo2:lo2, di:di}
      IF gridtype EQ 0 THEN res = create_struct(res, 'dj', dj) $
      ELSE res = create_struct(res, 'n', n)
      RETURN, res
    END
; Mercator Projection Grid
    gridtype EQ 1:
; Gnomonic Projection Grid
    gridtype EQ 2:
; Lambert Conformal, secant or tangent, conical or bipolar (normal or
; oblique) Projection Grid
    gridtype EQ 3:
; Polar Stereographic Projection Grid
    gridtype EQ 5:
; Oblique Lambert conformal, secant or tangent, conical or bipolar,
; projection
    gridtype EQ 13:
; Spherical Harmonic Coefficients
    gridtype EQ 50:
; Space view perspective or orthographic grid
    gridtype EQ 90:
; reserved - see Manual on Codes
    ELSE:
  ENDCASE
;
  RETURN, -1
END