AUTOREG -- ImageLock Data Fusion Registration

The automatic registration function. Given a reference image, and a second input image, referred to as the target image, it will apply a filtering and correlation process to determine the best affine transformation for registering the input image to the reference image.

PARAMETERS

AUTOREG is controlled by the following global parameters 

Name     Prompt                                  Count     Type
FILI_REF Reference input image file              1-64      Char
DBIC_REF Reference image channel                 1         Int
FILI_IMA Input Image to be registered            1-64      Char
DBIC_IMA Image to be registered channel          1         Int
FILO     Registered image output file            1-64      Char
WCHUNKS  Whitening chunksize                     1         Int
CG_XOFF  Correlation Grid X offset               1         Int
CG_YOFF  Correlation Grid Y offset               1         Int
PATCH    Correlation patchsize                   1         Int
SEARCH   Correlation search window               1         Int
PFA      Probability of False Alarm              1         Float
ISONOFAC Isolated Noise Factor                   1         Float

FILI_REF

Specifies the input reference image file to register the FILI_IMA image to. 

 EASI>FILI_REF = "filename.pix"

DBIC_REF

Specifies the PCI image channel where the reference image file is located. If autoreg is used in conjunction with an EASI Script, this parameter can be reassigned to specify the correct working image channel being used. 

 EASI>DBIC_REF = 2
 EASI>DBIC_REF =                | defaults to 1

FILI_IMA

Specifies the input image file to be registered to the reference image FILI_REF. 

 EASI>FILI_IMA = "filename.pix"

DBIC_IMA

Specifies the PCI image channel where the FILI_IMA is located. If autoreg is used in conjunction with an EASI Script, this parameter can be reassigned to specify the correct working image channel being used. 

 EASI>DBIC_IMA = 4
 EASI>DBIC_IMA =                 | defaults to 1

FILO

Specifies the registered image output file to contain the output of registering FILI_IMA to FILI_REF. 

 EASI>FILO = "filename.pix"

WCHUNKS

Specifies the size of the chunk of data used to whiten (edge enhance) the FILI_REF and FILI_IMA images. This value must be a power of 2, and 32 or less. Normally the value 32 is best, though a value of 16 will speed processing up at some cost in reduced accuracy. 

 EASI> WCHUNKS = 16
 EASI> WCHUNKS =                  | defaults to 32 pixels

CG_XOFF

Specifies the correlation grid X offset. This offset is used to make sure that no edge effects are included in the whitening or the correlation of the data.

Minimum = 32. CG_XOFF must be >= 1/2 Search size. 

 EASI>CG_XOFF = 64
 EASI>CG_XOFF =                  | defaults to 128

CG_YOFF

Specifies the correlation grid Y offset. This offset is used to make sure that no edge effects are included in the whitening or the correlation of the data.

Minimum = 32. CG_YOFF must be >= 1/2 Search size. 

 EASI>CG_YOFF = 64
 EASI>CG_YOFF =                  | defaults to 128

PATCH

Specifies the correlation patch size. Sets the size of the image chip for cross-correlation. This parameter can usually be set between 16 and 32. 

 EASI>PATCH = 32
 EASI>PATCH =                     | defaults to 16

SEARCH

Specifies the correlation search window. Sets the extent of the correlation search range which is the expected mis-registration. 

 EASI>SEARCH = 64
 EASI>SEARCH =                   | defaults to 32
Search size >= Patch size.

PFA

Specifies the probability of false alarm. Decreasing this parameter prunes out control points that are not likely to be due to image structure. 

 EASI>PFA = 0.2
 EASI>PFA =                      | defaults to 0.10

ISONOFAC

Specifies the isolated noise factor. This parameter is not normally set by the user. 

 EASI>ISONOFAC = 0.2
 EASI>ISONOFAC =                 | defaults to 0.10

EXAMPLE

Register channel 2 with channel 1 as the reference image. Place the output GCP points into a new GCP segment on the FILO file. Set the Patch to 16 and then set the SEARCH to 32. Use a correlation grid offset of 128 pixels in the x and y dimensions (CG_XOFF and CG_YOFF). The probability of false alarm (PFA) and the isolation noise factor (ISONOFAC) are both set to .1 and 32 whitening chunks (WCHUNKS) are chosen. 

EASI>FILI_REF = "pan_2000.pix"
EASI>DBIC_REF = 1
EASI>FILI_IMA = "pan_2000.pix"
EASI>DBIC_IMA = 2
EASI>FILO     = "pan_2000.pix"
EASI>WCHUNKS  = 32
EASI>CG_XOFF  = 128
EASI>CG_YOFF  = 128
EASI>PATCH    = 16
EASI>SEARCH   = 32
EASI>PFA      = 0.1
EASI>ISONOFAC = 0.1

CHOOSING INPUT PARAMETERS

In order to correctly set the parameters for AUTOREG, follow these guidelines to get a good initial estimate of the parameter values: 

  1. Choose the patchsize (PATCH) between 16 and 32.
  2. Choose the search window size (SEARCH >= PATCH)
  3. Make CG_XOFF, CG_YOFF >= 1/2 SEARCH > 32 ;
     also make CG_XOFF = CG_YOFF for square images.
  4. Set the probability of false alarm (PFA) about equal to .10.
     Lower the PFA for a better correlation.
     Raise the PFA for a looser correlation.
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