Use this procedure to georeference a file from a GLT file, which contains the map projection information for the specified input file. Each pixel location in the input file is directly mapped to a specified output map location. Use ENVI_GLT_DOIT to build the input GLT file.


ENVI_DOIT, 'ENVI_GEOREF_FROM_GLT_DOIT' [, BACKGROUND=value], FID=file ID [, GLT_DIMS=array], GLT_FID=file ID, /IN_MEMORY [, KERNEL_MAX=value] [, KERNEL_MIN=value] [, MIN_PIXELS=value], OUT_NAME=string, POS=array [, R_FID=variable] [, SGL_NAME=string [, /SUBSET] [, /SUPER]


BACKGROUND (optional)

Use this keyword to specify the value for all background pixels. The default is 0.


The file ID (FID) is a long-integer scalar with a value greater than 0. An invalid FID has a value of -1. The FID is provided as a named variable by any routine used to open or select a file. Often, the FID is returned from the keyword R_FID in the ENVIRasterToFID routine. Files are processed by referring to their FIDs. If you work directly with the file in IDL, the FID is not equivalent to a logical unit number (LUN).

GLT_DIMS (optional)

Use this keyword to specify the spatial dimensions on which to perform the operation. GLT_DIMS is a five-element array of long integers with the following definitions:

  • GLT_DIMS[0]: A pointer to an open ROI; use only in cases where ROIs define the spatial subset. Otherwise, set to -1L.
  • GLT_DIMS[1]: The starting sample number. The first x pixel is 0.
  • GLT_DIMS[2]: The ending sample number
  • GLT_DIMS[3]: The starting line number. The first y pixel is 0.
  • GLT_DIMS[4]: The ending line number


Use this keyword to specify the file ID of the input GLT file. This value is returned from the keyword R_FID in the ENVI_OPEN_FILE procedure. GLT_FID is a long integer with a value greater than 0. An invalid file ID has a value of -1.


Set this keyword to specify that output should be stored in memory. If you do not set IN_MEMORY, output will be stored on disk and you must specify OUT_NAME (see below).


Use this keyword to specify the maximum kernel size, which is used with KERNEL_MIN as a set of resampling parameters.

KERNEL_MIN (optional)

Use this keyword to specify the minimum kernel size, which is used in the resampling unless the kernel contains fewer than the minimum number of pixels to resample, or valid pixels. If the former, then the kernel size increases until either the minimum number of valid pixels is met or the maximum kernel size is met.

MIN_PIXELS (optional)

Use this keyword to specify the minimum number of pixels. If the maximum kernel size has fewer than the minimum number of pixels, then the output pixel value is set to the background value.


Use this keyword to specify a string with the output filename for the resulting data. If you set the keyword IN_MEMORY, you do not need to specify OUT_NAME.


Use this keyword to specify an array of band positions, indicating the band numbers on which to perform the operation. This keyword indicates the spectral subset of bands to use in processing. POS is an array of long integers, ranging from 0 to the number of bands minus 1. Specify bands starting with zero (Band 1=0, Band 2=1, etc.) For example, to process only Bands 3 and 4 of a multi-band file, POS=[2, 3].

POS is typically used with individual files. The example code below illustrates the use of POS for a single file with four bands of data:

envi_doit, 'envi_stats_doit', dims=dims, fid=fid, pos=pos, $
comp_flag=3, dmin=dmin, dmax=dmax, mean=mean, stdv=stdv, hist=hist

But what if you need to create an output file consisting of data from different bands, each from different files? Library routines such as CF_DOIT and ENVI_LAYER_STACKING_DOIT can accomplish this, but they use the POS keyword differently. Suppose you have four files, test1, test2, test3, and test4, with corresponding FIDs of fid1, fid2, fid3, and fid4, respectively. In the following example, you want Band 3 from test1 in the first position, Band 2 from test2 in the second position, Band 6 from test3 in the third position, and Band 4 from test4 in the fourth position. The code should be as follows:

  fid_array = [fid1,fid2,fid3,fid4]
envi_doit, 'cf_doit', dims=dims, fid=fid_array

R_FID (optional)

ENVI Classic library routines that result in new images also have an R_FID, or “returned FID.” This is simply a named variable containing the file ID to access the processed data. Specifying this keyword saves you the step of opening the new file from disk.

SGL_NAME (optional)

Use this keyword to specify the filename of the super GLT file (on disk) that results from ENVI_GLT_DOIT. This keyword is required if you set the SUPER keyword.

SUBSET (optional)

Set this keyword to indicate that the file specified by FID is a subset of the GLT file. Output dimensions will be determined by the minimum and maximum samples and lines of the GLT file. If you set this keyword, then GLT_DIMS is ignored.

SUPER (optional)

Set this keyword to perform a super GLT operation. If you set this keyword, you must also specify SGL_NAME.

API Version