The ENVI_SEAWIFS_GEOREF_DOIT procedure georeferences HDF- and CEOS-format SeaWiFS data. This procedure extracts header information to perform a precision geocoding of SeaWiFS data based on a complete geometry model of the earth and satellite orbit.

Syntax

ENVI_DOIT, 'ENVI_SEAWIFS_GEOREF_DOIT' [, BACKGROUND=value] [, CEOS=string] [, DEGREE=value], DIMS=array, FID=file ID [, GCP_NAME=string] [, GCP_PTS=variable], /IN_MEMORY [, OUT_BNAME=string array], OUT_NAME=string, OUT_PROJ=structure, POS=array [, /PTS_ONLY] [, R_FID=variable] [, WARP_X=integer] [, WARP_Y=integer], WARP_METHOD={0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8} [, ZERO_EDGE=0]

Keywords

BACKGROUND (optional)

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

CEOS (optional)

Use this keyword to specify the name of the CEOS annotation file containing the geospatial parameters.

If you do not set this keyword, the file is assumed to be in HDF format.

DEGREE (optional)

Use this keyword to specify the degree of the polynomial warp when METHOD=3, 4, or 5. The default is DEGREE=1.

DIMS

The “dimensions” keyword is a five-element array of long integers that defines the spatial subset (of a file or array) to use for processing. Nearly every time you specify the keyword FID, you must also specify the spatial subset of the corresponding file (even if the entire file, with no spatial subsetting, is to be processed).

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

To process an entire file (with no spatial subsetting), define DIMS as shown in the following code example. This example assumes you have already opened a file using ENVI_SELECT or ENVI_PICKFILE:

  envi_file_query, fid, dims=dims

FID

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).

GCP_NAME (optional)

Use this keyword to specify the name of the output file that contains the ground control points (GCPs). If you do not set this keyword, the points are not saved to disk.

GCP_PTS (optional)

Use this keyword to specify a named variable that contains the GCPs.

IN_MEMORY

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).

OUT_BNAME (optional)

Use this keyword to specify a string array of output band names.

OUT_NAME

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.

OUT_PROJ

Use this keyword to specify the projection of the resulting data. You cannot set OUT_PROJ to the Arbitrary projection. OUT_PROJ is a projection structure returned from ENVI_PROJ_CREATE or ENVI_GET_PROJECTION.

POS

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:

  pos=[0,1,2,3]
                  
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]
                  
pos=[2,1,5,3]
                  
envi_doit, 'cf_doit', dims=dims, fid=fid_array
                  
out_name='test_composite_file'

PTS_ONLY (optional)

Set this keyword to compute only the GCPs. If you set this keyword, the input image is not warped.

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.

WARP_X (optional)

Use this keyword to specify the number of x warp points to use for the georeferencing process. The default value is 50.

WARP_Y (optional)

Use this keyword to specify the number of y warp points to use for the georeferencing process. The default value is 50.

WARP_METHOD (optional)

Use this keyword to specify an integer value indicating a combination of methods used to warp and resample the image.

  • 0: RST with nearest neighbor (default)
  • 1: RST with bilinear
  • 2: RST with cubic convolution
  • 3: Polynomial with nearest neighbor
  • 4: Polynomial with bilinear
  • 5: Polynomial with cubic convolution
  • 6: Triangulation with nearest neighbor
  • 7: Triangulation with bilinear
  • 8: Triangulation with cubic convolution

ZERO_EDGE (optional)

Set this keyword to set the edges outside of any triangles for the triangulation method to the value specified by the BACKGROUND keyword. Use the ZERO_EDGE keyword only when WARP_METHOD=6, 7, or 8.

The ZERO_EDGE keyword is set by default. To disable this default behavior, explicitly set the ZERO_EDGE keyword to 0.

API Version

4.2