[67] | 1 | NAME: |
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| 2 | |
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| 3 | ncdf_quickread |
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| 4 | |
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| 5 | |
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| 6 | SYNOPSIS: |
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| 7 | |
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| 8 | This is a routine for reading variables into an IDL session from a |
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| 9 | NetCDF file, in just a very few commands. |
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| 10 | |
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| 11 | |
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| 12 | DESCRIPTION: |
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| 13 | |
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| 14 | 1) Ensure that the supplied routines are installed in your IDL_PATH. |
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| 15 | |
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| 16 | ncdf_quickread.pro |
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| 17 | ncdf_quickread_helper.pro |
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| 18 | |
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| 19 | 2) Set the string variable NCFILE to the NetCDF filename you wish to write, |
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| 20 | For example: |
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| 21 | |
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| 22 | ncfile='myfile.nc' |
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| 23 | |
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| 24 | 3) Optionally set the following variables: |
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| 25 | |
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| 26 | ncprefix : prefix to prepend to all variable names when importing |
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| 27 | from NetCDF variable name into IDL namespace |
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| 28 | |
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| 29 | ncverbose : set equal to 1 if you want to include attributes |
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| 30 | |
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[70] | 31 | ncfields : Set to a string which is a space-separated list of |
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| 32 | variables to read. Only the variables specified will be |
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| 33 | read in (and where ncverbose is set, only the attributes |
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| 34 | associated with these variables and the global attributes). |
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| 35 | If unset or the null string, then reads all fields. |
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| 36 | |
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[67] | 37 | 4) Type: @ncdf_quickread |
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| 38 | |
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| 39 | |
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| 40 | USAGE EXAMPLES: |
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| 41 | |
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| 42 | 1) SIMPLE EXAMPLE. |
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| 43 | |
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| 44 | => You have the following NetCDF file: |
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| 45 | "ncdump -h mslp.djf.nc" reports the following: |
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| 46 | |
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| 47 | netcdf mslp.djf { |
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| 48 | dimensions: |
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| 49 | longitude = 96 ; |
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| 50 | latitude = 73 ; |
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| 51 | msl = 1 ; |
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| 52 | t = UNLIMITED ; // (100 currently) |
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| 53 | variables: |
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| 54 | float longitude(longitude) ; |
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| 55 | longitude:units = "degrees_east" ; |
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| 56 | longitude:point_spacing = "even" ; |
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| 57 | longitude:modulo = " " ; |
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| 58 | float latitude(latitude) ; |
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| 59 | latitude:units = "degrees_north" ; |
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| 60 | latitude:point_spacing = "even" ; |
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| 61 | float msl(msl) ; |
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| 62 | msl:units = "level" ; |
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| 63 | msl:positive = "up" ; |
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| 64 | float t(t) ; |
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| 65 | t:units = "days since 1991-09-01 00:00:00" ; |
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| 66 | t:calendar = "360_day" ; |
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| 67 | t:time_origin = "01-SEP-1991:00:00:00" ; |
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| 68 | float p_2(t, msl, latitude, longitude) ; |
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| 69 | p_2:source = "Unified Model Output (Vn 4.6):" ; |
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| 70 | p_2:name = "p_2" ; |
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| 71 | p_2:title = "PRESSURE AT MEAN SEA LEVEL" ; |
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| 72 | p_2:date = "01/09/91" ; |
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| 73 | p_2:time = "00:00" ; |
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| 74 | p_2:long_name = "PRESSURE AT MEAN SEA LEVEL" ; |
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| 75 | p_2:units = "Pa" ; |
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| 76 | p_2:missing_value = 2.e+20f ; |
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| 77 | p_2:_FillValue = 2.e+20f ; |
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| 78 | p_2:valid_min = 97130.55f ; |
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| 79 | p_2:valid_max = 103777.6f ; |
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| 80 | |
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| 81 | // global attributes: |
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| 82 | :history = "Thu Oct 2 14:34:56 BST 2003 - XCONV V1.90 04-September-2002" ; |
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| 83 | } |
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| 84 | |
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| 85 | => You issue the following commands: |
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| 86 | |
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| 87 | ncfile='mslp.djf.nc' |
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| 88 | @ncdf_quickread |
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| 89 | |
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| 90 | => This imports the following into IDL: |
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| 91 | |
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| 92 | LATITUDE FLOAT = Array[73] |
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| 93 | LONGITUDE FLOAT = Array[96] |
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| 94 | MSL FLOAT = 0.00000 |
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| 95 | P_2 FLOAT = Array[96, 73, 100] |
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| 96 | T FLOAT = Array[100] |
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| 97 | |
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| 98 | |
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| 99 | By the way, also a few variables get set as a side-effect, |
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| 100 | but these can be ignored. |
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| 101 | |
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| 102 | NCFILE STRING = 'mslp.djf.nc' |
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| 103 | NCPREFIX UNDEFINED = <Undefined> |
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| 104 | NCVERBOSE UNDEFINED = <Undefined> |
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| 105 | __COMMANDS STRING = Array[8] |
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| 106 | __LOOP INT = 8 |
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| 107 | __NCID LONG = 1 |
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| 108 | |
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| 109 | |
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| 110 | 2) MORE COMPLEX EXAMPLE. |
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| 111 | |
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| 112 | => You have the same NetCDF file shown above. |
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| 113 | |
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| 114 | => You issue the following commands: |
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| 115 | |
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| 116 | ncfile='mslp.djf.nc' |
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| 117 | ncverbose=1 |
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| 118 | ncprefix='djf_' |
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| 119 | @ncdf_quickread |
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| 120 | |
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| 121 | => This imports the following into IDL: |
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| 122 | |
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| 123 | DJF_HISTORY STRING = 'Thu Oct 2 14:34:56 BST 2003 - XCONV V1.90 04'... |
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| 124 | DJF_LATITUDE FLOAT = Array[73] |
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| 125 | DJF_LATITUDE_POINT_SPACING |
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| 126 | STRING = 'even' |
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| 127 | DJF_LATITUDE_UNITS |
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| 128 | STRING = 'degrees_north' |
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| 129 | DJF_LONGITUDE FLOAT = Array[96] |
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| 130 | DJF_LONGITUDE_MODULO |
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| 131 | STRING = ' ' |
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| 132 | DJF_LONGITUDE_POINT_SPACING |
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| 133 | STRING = 'even' |
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| 134 | DJF_LONGITUDE_UNITS |
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| 135 | STRING = 'degrees_east' |
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| 136 | DJF_MSL FLOAT = 0.00000 |
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| 137 | DJF_MSL_POSITIVE |
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| 138 | STRING = 'up' |
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| 139 | DJF_MSL_UNITS STRING = 'level' |
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| 140 | DJF_P_2 FLOAT = Array[96, 73, 100] |
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| 141 | DJF_P_2_DATE STRING = '01/09/91' |
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| 142 | DJF_P_2_LONG_NAME |
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| 143 | STRING = 'PRESSURE AT MEAN SEA LEVEL' |
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| 144 | DJF_P_2_MISSING_VALUE |
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| 145 | STRING = ' 2.00000e+20' |
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| 146 | DJF_P_2_NAME STRING = 'p_2' |
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| 147 | DJF_P_2_SOURCE STRING = 'Unified Model Output (Vn 4.6):' |
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| 148 | DJF_P_2_TIME STRING = '00:00' |
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| 149 | DJF_P_2_TITLE STRING = 'PRESSURE AT MEAN SEA LEVEL' |
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| 150 | DJF_P_2_UNITS STRING = 'Pa' |
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| 151 | DJF_P_2_VALID_MAX |
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| 152 | STRING = ' 103778.' |
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| 153 | DJF_P_2_VALID_MIN |
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| 154 | STRING = ' 97130.5' |
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| 155 | DJF_P_2__FILLVALUE |
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| 156 | STRING = ' 2.00000e+20' |
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| 157 | DJF_T FLOAT = Array[100] |
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| 158 | DJF_T_CALENDAR STRING = '360_day' |
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| 159 | DJF_T_TIME_ORIGIN |
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| 160 | STRING = '01-SEP-1991:00:00:00' |
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| 161 | DJF_T_UNITS STRING = 'days since 1991-09-01 00:00:00' |
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| 162 | |
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| 163 | BUGS: |
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| 164 | |
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| 165 | => Not sure. |
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| 166 | |
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| 167 | |
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| 168 | LIMITATIONS: |
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| 169 | |
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| 170 | => IDL variable names are case-insensitive, so there could be a namespace |
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| 171 | conflict if variable names in the NetCDF file differ only in case |
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| 172 | |
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| 173 | AUTHOR: |
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| 174 | |
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| 175 | CDF2IDL original: S. Rupert |
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| 176 | Adapted by Alan Iwi <A.M.Iwi@rl.ac.uk> |
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| 177 | |
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| 178 | |
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| 179 | COPYRIGHT: |
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| 180 | |
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| 181 | This routine is based on CDF2IDL which is in the public domain. |
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| 182 | The modifications by Alan Iwi are also in the public domain. |
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| 183 | |
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| 184 | But the IDL program itself is subject to copyright restrictions. |
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| 185 | |
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| 186 | |
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| 187 | SEE ALSO: |
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| 188 | |
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| 189 | CDF2IDL original: http://www-c4.ucsd.edu/~cids/software/visual.html |
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