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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