NetCDF转成ENVI标准格式
NetCDF（http://www.unidata.ucar.edu/software/netcdf/）格式是比较常见的地学数据存储格式,很多数据都是NetCDF格式存储，读写NetCDF有很多库，如C++，java，Fortran，但是，这些库都是底层，编译比较麻烦；其次，用底层的库将NetCDF格式和其他数据（如，shp矢量数据）结合处理是比较麻烦的，如Fortran,要处理结合shp和NetCDF数据还需要FortranGIS（http://fortrangis.sourceforge.net/）支持，同样需要编译；同时，像matlab和IDL是高级语言，能直接读写NetCDF，并且擅长于栅格矩阵运算，由于和ENVI结合紧密，IDL对shp的支持更优，所以，难免需要将NetCDF格式转成ENVI标准格式，用于显示和后期处理。
1.原始NetCDF【示例数据SA.nc下载地址】
Panoply（http://www.giss.nasa.gov/tools/panoply/）显示的信息如下
属性信息：
空间信息：
2.转换成ENVI标准格式信息，ENVI显示如下如图：
属性信息：
空间信息：
3.代码（需要ENVI+IDL运行 支持批处理）
;+
; ;**********************************************************
; Author: wuxb
; Email: wavelet2008@163.com
; NAME:
; D:\workspace\Tech\Code\IDL\ENVI_IDL4.7\SoilTextureProduce\DataPreprocessing\NCData2ENVI.pro
; PARAMETERS:
; 1、NcPath
; 2、EnviPath
; Write by :
; 2015-4-23 9:29:02
;;MODIFICATION HISTORY:
;; Modified :
;***********************************************************
;-
PRO NCDATA2ENVI, NcDirectory = NcDirectory, ENVIDirectory = ENVIDirectory
;**************************************************************************
;
; 1) Initialize the Common variables
;
;**************************************************************************
;just for Test
NcDirectory = 'D:\Temp\Data\Input\'
ENVIDirectory = 'D:\Temp\Data\Output\'
;**************************************************************************
;
; 2) Get the files to be convert
;
;**************************************************************************
NCFilePaths = FILE_SEARCH(NcDirectory,'*.NC', COUNT = nCount, /TEST_READ, /FULLY_QUALIFY_PATH)
IF(nCount LE 0) THEN RETURN
PRINT,'Procedure begins at ' + STRING(SYSTIME(/UTC))
FOR i=0, nCount-1 DO BEGIN
;Open Nc File
NID = NCDF_OPEN(NCFilePaths[i], /nowrite )
;Inquire about this file; returns structure
File_Info = NCDF_INQUIRE(NID)
;define the dimensions of this file
NS = 0L
NL = 0L
NB = 0L
;**************************************************************************
; 1) read dim info
;**************************************************************************
FOR dimid=0, FILE_INFO.NDIMS -1 DO BEGIN
NCDF_DIMINQ, NID, Dimid, Name, Size
SWITCH Name OF
"lon": BEGIN
NS = Size
BREAK
END
"lat": BEGIN
NL = Size
BREAK
END
"depth": BEGIN
NB = Size
BREAK
END
ELSE: BEGIN
PRINT, 'There is no Dim'
END
ENDSWITCH
ENDFOR
;**************************************************************************
; 2) read data info
;**************************************************************************
;define proj request
StartX = 0.0;
StartY = 0.0;
EndX = 0.0;
EndY = 0.0;
GridSize = 0.0;
ndepth = FLTARR(NB)
FOR Varid=0, FILE_INFO.NVARS-1 DO BEGIN
IsWRITE = 1;
; inquire about the variable; returns structure
VAR = NCDF_VARINQ( NID, Varid )
;read data
dataID = NCDF_VARID(NID, VAR.NAME)
NCDF_VARGET, NID, dataID, Data
SWITCH VAR.NAME OF
"lon": BEGIN
StartX = Data[0];
nData = N_ELEMENTS(Data)
EndX = Data(nData-1)
IsWRITE = 0
BREAK
END
"lat": BEGIN
StartY = Data[0];
nData = N_ELEMENTS(Data)
EndY = Data(nData-1)
IsWRITE = 0
BREAK
END
"depth": BEGIN
ndepth = Data
IsWRITE = 0
BREAK
END
ENDSWITCH
;**************************************************************************
;1) IF No project then Creat project
;**************************************************************************
; Projection
; GridSize = 0 illustrate iMap is null
IF (GridSize EQ 0) AND IsWRITE THEN BEGIN
GridSize = (ROUND(EndX) ROUND(StartX)) / FLOAT(NS)
; start point
iProj = ENVI_PROJ_CREATE(/GEOGRAPHIC)
; Create the map information
ps = [GridSize, GridSize]
mc = [0D, 0D, StartX, EndY]
Datum = 'WGS-84'
Units = ENVI_TRANSLATE_PROJECTION_UNITS ('Degrees')
iMap = ENVI_MAP_INFO_CREATE(/GEOGRAPHIC,MC=MC,PS=PS,PROJ=iProj,UNITS=Units)
ENDIF
;**************************************************************************
; 2) Creat Envi File
;**************************************************************************
IF IsWRITE THEN BEGIN
OutFilePath = ENVIDirectory + VAR.NAME
OPENW, HData, OutFilePath, /GET_LUN
WRITEU, HData,REVERSE(Data,2)
FREE_LUN, HData
DATA_TYPE = 4
DataType = VAR.DATATYPE
SWITCH VAR.DATATYPE OF
"BYTE": BEGIN
DATA_TYPE = 1
BREAK
END
"CHAR": BEGIN
DATA_TYPE = 1
BREAK
END
"INT": BEGIN
DATA_TYPE = 2
BREAK
END
"LONG": BEGIN
DATA_TYPE = 3
BREAK
END
"FLOAT": BEGIN
DATA_TYPE = 4
BREAK
END
"DOUBLE": BEGIN
DATA_TYPE = 5
BREAK
END
ENDSWITCH
; Edit the envi header file
ENVI_SETUP_HEAD,FNAME=OutFilePath,NS=NS,NL=NL,NB=NB,INTERLEAVE=0,$
DATA_TYPE=DATA_TYPE,OFFSET=0,MAP_INFO=iMap,BNAMES=[VAR.NAME],/WRITE,$
/OPEN,R_FID=Data_FID
;**************************************************************************
; 3) read all attributes update Herder file
;**************************************************************************
;Set the header value
ENVI_ASSIGN_HEADER_VALUE, FID=Data_FID, KEYWORD ='Author', VALUE = "Wuxb"
ENVI_ASSIGN_HEADER_VALUE, FID=Data_FID, KEYWORD ='Soil Depth', VALUE = ndepth, PRECISION=5
FOR VarAttID =0, VAR.NATTS -1 DO BEGIN
AttName = NCDF_ATTNAME( NID, Varid, VarAttID )
NCDF_ATTGET, NID, varid, AttName, AttValue
ENVI_ASSIGN_HEADER_VALUE, FID=Data_FID, KEYWORD = AttName, VALUE = STRING(AttValue)
ENDFOR
;Write the values to the file header
ENVI_WRITE_FILE_HEADER, Data_FID
;remove file
ENVI_FILE_MNG, ID=Data_FID, /REMOVE
ENDIF
ENDFOR
ENDFOR
PRINT, 'Procedure ends at ' + SYSTIME(/UTC)
END