Class WcsConstants

Namespace

FitsModel.Wcs

Assembly

FitsModel.dll

The keywords given below constitute a complete set of fun- damental attributes for a WCS description.Although their inclu- sion in an HDU is optional, FITS writers should include a com- plete set of keywords when describing a WCS.In the event that some keywords are missing, default values must be assumed, as specified below.

public static class WcsConstants

Inheritance

object

WcsConstants

Inherited Members

object.GetType()

object.MemberwiseClone()

object.ToString()

object.Equals(object)

object.Equals(object, object)

object.ReferenceEquals(object, object)

object.GetHashCode()

Fields

CDMatrixPrefix

CDi j – [floating point; defaults: 0.0, but see below]. Linear transformation matrix(with scale) between Pixel Axes j and Intermediate-coordinate Axes i.This nomenclature is equivalent to PCi j when CDELTi is unity. The CDi j matrix must not be singular.Note that the CDi j formalism is an ex- clusive alternative to PCi j, and the CDi j and PCi j keywords must not appear together within an HDU.
In addition to the restrictions noted above, if any CDi j keywords are present in the HDU, all other unspecified CDi j keywords shall default to zero.If no CDi j keywords are present then the header shall be interpreted as being in PCi j form whether or not any PCi j keywords are actually present in the HDU. Some non-linear algorithms that describe the transformation between pixel and intermediate-coordinate axes require param- eter values. A few non-linear algorithms also require character- valued parameters, e.g., table lookups require the names of the table extension and the columns to be used.Where necessary parameter values must be specified via the following keywords.

public const string CDMatrixPrefix = "CD"

Field Value

string

CenterPixelPrefix

CRPIXj – [floating point; indexed; default: 0.0]. Location of the reference point in the image for Axis j corresponding to r j in Eq. (9). Note that the reference point may lie outside the image and that the first pixel in the image has pixel coordi- nates(1.0, 1.0, . . .).

public const string CenterPixelPrefix = "CRPIX"

Field Value

string

CenterValuePrefix

CRVALi – [floating point; indexed; default: 0.0]. World- coordinate value at the reference point of Axis i.

public const string CenterValuePrefix = "CRVAL"

Field Value

string

CoordRandErrorPrefix

CRDERi – [floating point; default: 0.0]. Random error in Coordinate i, which must be non-negative.
While not essential for a complete specification of an image WCS, can be extremely useful for read- ers to interpret the accuracy of the WCS representation of the image.
These values should give a representative average value of the error over the range of the coordinate in the HDU.The total error in the coordinates would be given by summing the individual errors in quadrature.

public const string CoordRandErrorPrefix = "CRDER"

Field Value

string

CoordSysErrorPrefix

CSYERi – [floating point; default: 0.0]. Systematic error in Coordinate i, which must be non-negative.
While not essential for a complete specification of an image WCS, can be extremely useful for read- ers to interpret the accuracy of the WCS representation of the image.
These values should give a representative average value of the error over the range of the coordinate in the HDU.The total error in the coordinates would be given by summing the individual errors in quadrature.

public const string CoordSysErrorPrefix = "CSYER"

Field Value

string

CoordinateDeltaPrefix

CDELTi – [floating point; indexed; default: 1.0]. Increment of the world coordinate at the reference point for Axis i.The value must not be zero.

public const string CoordinateDeltaPrefix = "CDELT"

Field Value

string

CoordinateRotationPrefix

CROTAi – [floating point; indexed; default: 0.0]. The amount of rotation from the standard coordinate system to a different coordinate system.Further use of this of this keyword is dep- recated, in favor of the newer formalisms that use the CDi j or PCi j keywords to define the rotation.

public const string CoordinateRotationPrefix = "CROTA"

Field Value

string

CoordinateTypePrefix

CTYPEi – [string; indexed; default: ' ' (i.e. a linear, undefined axis)]. Type for the Intermediate-coordinate Axis i.Any co- ordinate type that is not covered by this Standard or an offi- cially recognized FITS convention shall be taken to be linear. All non-linear coordinate system names must be expressed in ‘4–3’ form: the first four characters specify the coordinate type, the fifth character is a hyphen (‘-’), and the remain- ing three characters specify an algorithm code for computing the world coordinate value. Coordinate types with names of fewer than four characters are padded on the right with hy- phens, and algorithm codes with fewer than three charac- ters are padded on the right with blanks11. Algorithm codes should be three characters

public const string CoordinateTypePrefix = "CTYPE"

Field Value

string

CoordinateUnitPrefix

CUNITi – [string; indexed; default: ' ' (i.e., undefined)]. Physical units of CRVAL and CDELT for Axis i.Note that units should always be specified (see Sect. 4.3). Units for celestial coordinate systems defined in this Standard must be degrees.

public const string CoordinateUnitPrefix = "CUNIT"

Field Value

string

PCMatrixPrefix

PCi j – [floating point; defaults: 1.0 when i = j, 0.0 oth- erwise]. Linear transformation matrix between Pixel Axes j and Intermediate-coordinate Axes i.The PCi j matrix must not be singular.

public const string PCMatrixPrefix = "PC"

Field Value

string

PSMatrixPrefix

PSi m – [string]. Character-valued parameters for Intermediate- world-coordinate Axis i, where m is the parameter number. Leading zeros must not be used, and m may have only val- ues in the range 0 through 99, and that are defined for the particular non-linear algorithm.

public const string PSMatrixPrefix = "PS"

Field Value

string

PVMatrixPrefix

PVi m – [floating point]. Numeric parameter values for Intermediate-world-coordinate Axis i, where m is the param- eter number.Leading zeros must not be used, and m may have only values in the range 0 through 99, and that are de- fined for the particular non-linear algorithm.

public const string PVMatrixPrefix = "PV"

Field Value

string

WcsAxesKeyword

WCSAXES – [integer; default: NAXIS, or larger of WCS indices i or j]. Number of axes in the WCS description.This keyword, if present, must precede all WCS keywords except NAXIS in the HDU.The value of WCSAXES may exceed the number of pixel axes for the HDU.

public const string WcsAxesKeyword = "WCSAXES"

Field Value

string