If CLASSIFY is TRUE then a list of classifications that describe the properties of the transformation (parameters XFOR, YFOR, XINV and YINV) should be given. This is optional, but the information can be used to make other applications run more efficiently. Valid values are:

• LINEAR – Linear and preserves straight lines.

• INDEPENDENT – Preserves the independence of the axes.

• DIAGONAL – Preserves the axes themselves.

• ISOTROPIC – Preserves angles and shapes.

• POSITIVE_DET – A component of reflection is absent.

• NEGATIVE_DET – A component of reflection is present.

• CONSTANT_DET – The scale factor is constant.

• UNIT_DET – Areas (or volumes etc.) are preserved.

See SUN/61 Appendix B for more details of transformation classification and a table of the classifications of common mappings.

If TRTYPE="EXPRES" is chosen then this parameter decides whether or not a classification of the transformation using parameters XFOR, YFOR, XINV and YINV will be given. Classification is optional, but you should note that the information can be used to make other applications run more efficiently, and the lack of a classification may stop certain types of operation. See SUN/61 appendix B for details. Linear transformations are classified by this routine using the FITTYPE parameter. [FALSE]

These parameters supply the values of "sub-expressions" used in the expressions XFOR, YFOR, XINV and YINV. These parameters should be used when repeated expressions are present in complex transformations. Sub-expressions may contain references to other sub-expressions and constants (PA-PZ). An example of using sub-expressions is:

The type of fit specified by coefficients supplied via the TR parameter. Appropriate values are.

• 1 – shift of origin

• 2 – shift of origin and rotation

• 3 – shift of origin and magnification

• 4 – shift of origin, rotation and magnification (solid body)

• 5 – a full six parameter fit

The value of this parameter is used to classify the transformation (see the CLASS parameter). [5]

If MODE=‘ERASE’ and NAME=‘SET’, then this parameter indicates whether the CCD_SET coordinate frame should be removed from the World Coordinate System etension of the image as well. Since CCD_SET coordinates are usually a copy of another coordinate system, and mainly intended for Set-related registration, it is usually sensible to erase this coordinate frame when the rest of the Set header information has been erased. [TRUE]

A list specifying the names of the images whose CCDPACK extensions are to be modified. The image names should be separated by commas and may include wildcards.

A list specifying one or more position list names (only used if MODE = "ALIST" ). If a single name is given then this position list will be associated with all the input images. If a list of names is given then there should be as many names as input images. The order of the input image names is shown so that the correct correspondence may be achieved.

Position list names may NOT include wildcards. So a comma separated list of explicit names should be used and/or the names should be read from indirection files (the indirection indicator is "$$^").

Name of the CCDPACK logfile. If a null (!) value is given for this parameter then no logfile will be written, regardless of the value of the LOGTO parameter.

If the logging system has been initialised using CCDSETUP then the value specified there will be used. Otherwise, the default is "CCDPACK.LOG". [CCDPACK.LOG]

Every CCDPACK application has the ability to log its output for future reference as well as for display on the terminal. This parameter controls this process, and may be set to any unique abbreviation of the following:

• TERMINAL – Send output to the terminal only

• LOGFILE – Send output to the logfile only (see the LOGFILE parameter)

• BOTH – Send output to both the terminal and the logfile

• NEITHER – Produce no output at all

If the logging system has been initialised using CCDSETUP then the value specified there will be used. Otherwise, the default is "BOTH". [BOTH]

The mode of operation. Can be one of

• ALIST

• ERASE

• TRANSFORM

• INVERT

The "ALIST" option "associates" a position list(s) with images (this sets the "CURRENT_LIST" item). This is useful when importing position lists generated externally to CCDPACK.

The "ERASE" option removes a named item from image extensions. Two possible items are "CURRENT_LIST" and "TRANSFORM".

The "TRANSFORM" option allows the generation or import of transforms into image extensions. Transforms from other images may be copied. Linear transforms may be generated from the (6) coefficients. General transforms may be specified by algebraic-like expressions containing the functions allowed by the TRANSFORM package (SUN/61). If you intend to do this, see the related parameters (XFOR, YFOR, XINV, YINV, FA-FZ, PA-PZ, CLASSIFY and CLASS) and the examples section.

The "INVERT" option inverts the sense of transformations in the images. [ALIST]

If MODE = "ERASE" is chosen then the value of this parameter names the CCDPACK extension item of the input images which is to be erased. Typical items are "CURRENT_LIST", "TRANSFORM" and "SET". If "SET" is used, then the FIXWCS parameter will be used to decide whether to remove any CCD_SET-domain frames from the WCS component.

These parameters supply the values of constants used in the expressions XFOR, YFOR, XINV and YINV. Using parameters allows the substitution of repeated constants (with extended precisions?) using one reference. It also allows easy modification of parameterised expressions (expressions say with an adjustable centre) provided the application has not been used in the interim. The parameter PI has a default value of 3.14159265359D0. An example of using parameters is:

This maps (X,Y) to (R,THETA) about a specified centre.

If TRTYPE="STRUCT" is chosen then this parameter is used to access the HDS object which contains a transform structure to copy into the input images. The standard place to store a transform structure (in CCDPACK NDFs) is

• NDF_NAME.MORE.CCDPACK.TRANSFORM

If TRTYPE="COEFF" is chosen then the values of this parameter are the 6 coefficients of a linear transformation of the type:

The default is the identity transformation.

[0,1,0,0,0,1] [PA,PB,PC,PD,PE,PF]

If MODE = "TRANSFORM" is selected then this parameter specifies the type of transform which will be supplied. Valid returns are

• COEFF

• EXPRES

• STRUCT

If "COEFF" is chosen then the transform will be generated from the 6 coefficients of the equations:

supplied in the order PA,PB,PC,PD,PE,PF.

If "STRUCT" is chosen then an existing transformation structure will be copied into the extensions of the images. Note that no checking of the transforms validity will be made.

If "EXPRES" is chosen then the transformation will be specified using algebraic-like statements of the type:

The values of PA-PZ are accessed through the PA-PZ parameters. The PA-PZ’s are reserved for constants (FA-FZ are also reserved for repeated expressions). This example allows independent offsets and scales in X and Y. The inverse transformation must be supplied. [COEFF]

If TRTYPE="EXPRES" is chosen then this parameter’s value is the transformation that maps to the new X coordinate. The expression can contain constants, arithmetic operators ($+$,-,/,$\ast$,$\ast$$\ast$) and the functions described in SUN/61 (SIN,COS,TAN, etc.).

Constants may be specified using the special tokens PA-PZ. Prompts for the values for these tokens will then be made (this provides a mechanism for parameterising functions allowing trivial value changes). Sub-expressions which occur in many places may also be specified using the special tokens FA-FZ. These are prompted for and placed into the main expression. Sub-expressions may contain references to constants and other sub-expressions. An example expression is:

Note the single quotes. They are necessary to protect the equals sign.

If TRTYPE="EXPRES" is chosen then this parameter’s value is the transformation that maps to the old X coordinate - the inverse transformation of XFOR. The expression can contain constants, arithmetic operators ($+$,-,/,$\ast$,$\ast$$\ast$) and the functions described in SUN/61 (SIN,COS,TAN, etc.).

Constants may be specified using the special tokens PA-PZ prompts for values for these tokens will then be made (this provides a mechanism for parameterising functions allowing trivial values changes). Sub-expressions which occur in many places may also be specified using the special tokens FA-FZ. These are prompted for and placed into the main expression. Sub-expressions may contain references to constants and other sub-expressions. An example expression is:

Note the single quotes. They are necessary to protect the equals sign.

If TRTYPE="EXPRES" is chosen then this parameter’s value is the transformation that maps to the new Y coordinate. The expression can contain constants, arithmetic operators ($+$,-,/,$\ast$,$\ast$$\ast$) and the functions described in SUN/61 (SIN,COS,TAN, etc.).

Constants may be specified using the special tokens PA-PZ. Prompts for the values of these tokens will then be made (this provides a mechanism for parameterising functions allowing trivial value changes). Sub-expressions which occur in many places may also be specified using the special tokens FA-FZ. These are prompted for and placed into the main expression. Sub-expressions may contain references to constants and other sub-expressions. An example expression is:

Note the single quotes. They are necessary to protect the equals sign.

If TRTYPE="EXPRES" is chosen then this parameter’s value is the transformation that maps to the old Y coordinate - the inverse transformation of YFOR. The expression can contain constants, arithmetic operators ($+$,-,/,$\ast$,$\ast$$\ast$) and the functions described in SUN/61 (SIN,COS,TAN, etc.).

Constants may be specified using the special tokens PA-PZ. Prompts for the values of these tokens will then be made (this provides a mechanism for parameterising functions allowing trivial value changes). Sub-expressions which occur in many places may also be specified using the special tokens FA-FZ. These are prompted for and placed into the main expression. Sub-expressions may contain references to constants and other sub-expressions. An example expression is:

Note the single quotes. They are necessary to protect the equals sign.