| 1 | ;+ |
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| 2 | ; @file_comments |
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| 3 | ; |
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| 4 | ; @categories |
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| 5 | ; |
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| 6 | ; @param NUM |
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| 7 | ; |
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| 8 | ; @param RECSTART |
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| 9 | ; |
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| 10 | ; @param NI |
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| 11 | ; |
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| 12 | ; @param NJ |
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| 13 | ; |
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| 14 | ; @returns |
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| 15 | ; |
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| 16 | ; @restrictions |
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| 17 | ; |
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| 18 | ; @examples |
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| 19 | ; |
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| 20 | ; @history |
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| 21 | ; |
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| 22 | ; @version |
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| 23 | ; $Id$ |
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| 24 | ;- |
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| 25 | FUNCTION read_grib_bds, num, recstart, ni, nj |
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| 26 | ; |
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| 27 | compile_opt idl2, strictarrsubs |
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| 28 | ; |
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| 29 | offset = recstart+8 |
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| 30 | a = assoc(num, bytarr(1, /nozero), offset-1) |
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| 31 | sizepds = bit2int([binary(a[1]), binary(a[2]), binary(a[3])]) |
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| 32 | flag = binary(a[8]) |
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| 33 | gdsnotomitted = flag[0] |
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| 34 | bmsnotomitted = flag[1] |
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| 35 | ddd = bit2int([binary(a[27]), binary(a[28])], /checkneg) |
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| 36 | ; |
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| 37 | offset = offset+sizepds |
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| 38 | ; |
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| 39 | IF gdsnotomitted THEN BEGIN |
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| 40 | a = assoc(num, bytarr(1, /nozero), offset-1) |
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| 41 | sizedds = bit2int([binary(a[1]), binary(a[2]), binary(a[3])]) |
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| 42 | offset = offset+sizedds |
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| 43 | ENDIF |
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| 44 | ; |
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| 45 | IF bmsnotomitted THEN BEGIN |
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| 46 | a = assoc(num, bytarr(1, /nozero), offset-1) |
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| 47 | sizebms = bit2int([binary(a[1]), binary(a[2]), binary(a[3])]) |
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| 48 | offset = offset+sizebms |
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| 49 | ENDIF |
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| 50 | ; |
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| 51 | a = assoc(num, bytarr(1, /nozero), offset-1) |
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| 52 | ; |
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| 53 | sizebds = bit2int([binary(a[1]), binary(a[2]), binary(a[3])]) |
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| 54 | ; |
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| 55 | flags = binary(a[4]) |
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| 56 | ; BIT VALUE MEANING |
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| 57 | ; 1 0 Grid point data |
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| 58 | ; 1 Spherical Harmonic Coefficients |
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| 59 | ; 2 0 Simple packing |
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| 60 | ; 1 Second order ("Complex") Packing |
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| 61 | ; 3 0 Original data were floating point values |
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| 62 | ; 1 Original data were integer values |
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| 63 | ; 4 0 No additional flags at octet 14 |
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| 64 | ; 1 Octet 14 contains flag bits 5 - 12 |
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| 65 | ; 5 Reserved (set to 0) |
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| 66 | ; 6 0 Single datum at each grid point |
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| 67 | ; 1 Matrix of values at each grid point |
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| 68 | ; 7 0 No secondary bit maps |
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| 69 | ; 1 Secondary bit maps present |
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| 70 | ; 8 0 Second order values have constant width |
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| 71 | ; 1 Second order values have different widths |
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| 72 | ; 9-12 Reserved (set to 0) |
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| 73 | ; |
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| 74 | eee = bit2int([binary(a[5]), binary(a[6])], /checkneg) |
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| 75 | ; |
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| 76 | aaa = bit2int(binary(a[7]), /checkneg) |
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| 77 | bbb = bit2int([binary(a[8]), binary(a[9]), binary(a[10])]) |
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| 78 | IF aaa LT 0 THEN rrr = -2.^(-24) * bbb * 16.^(-aaa-64) $ |
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| 79 | ELSE rrr = 2.^(-24) * bbb * 16.^(aaa-64) |
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| 80 | ; |
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| 81 | nbits = (a[11])[0] |
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| 82 | CASE 1 OF |
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| 83 | flags[0] EQ 0 AND flags[1] EQ 0:BEGIN |
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| 84 | CASE nbits OF |
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| 85 | 8 :a = assoc(num, bytarr(ni, nj, /nozero), offset-1+12) |
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| 86 | 16:a = assoc(num, uintarr(ni, nj, /nozero), offset-1+12) |
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| 87 | 32:a = assoc(num, ulonarr(ni, nj, /nozero), offset-1+12) |
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| 88 | 64:a = assoc(num, ulon64arr(ni, nj, /nozero), offset-1+12) |
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| 89 | ELSE: |
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| 90 | ENDCASE |
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| 91 | END |
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| 92 | ENDCASE |
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| 93 | |
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| 94 | RETURN, (rrr+(a[0]*2.^(eee)))*10.^(-ddd) |
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| 95 | END |
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