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+AST Library
+-----------
+   A new release (V8.7.1) of the Starlink AST (astrometry) library is
+now available.
+
+   AST provides a comprehensive range of facilities for attaching
+world coordinate systems (such as RA/Dec, frequency, etc) to astronomical
+data, for retrieving and interpreting that information and for generating
+graphical output based on it.
+
+   The library should be of interest to anyone writing astronomical
+software which needs to manipulate coordinate system data, especially
+celestial coordinate systems. AST is portable and
+environment-independent.
+
+
+
+Main Changes in this Version
+----------------------------
+
+- The Moc class now supports version 1.1 of the the MOC recommendation.
+This includes new support for string and JSON encoded MOCs. See methods
+astGetMocString and astAddMocString in the Moc class, and also the new
+MocChan class.
+
+- The FitsChan class will now read FITS-WCS headers that have
+alternate axis descriptions but no primary axis descriptions.
+
+Main Changes in V8.7.0
+----------------------
+
+-  A new subclass of Region called "Moc" has been added. A Moc
+describes an arbitrary region of the sky in the form of a set of HEALPix
+cells using the IVOA Multi-Order Coverage scheme..
+
+-  The Region class has a new method called astGetRegionDisc, which
+returns the centre and radius of a disc that just encloses a
+2-dimensional Region.
+
+- The Bounded attribute defined by the Region class is now always
+non-zero for Regions defined within a SkyFrame, regardless of whether the
+Region has been negated. Previously, it was non-zero only if the Region
+had not been negated. Note, this change only affects Regions defined
+within SkyFrames.
+
+Main Changes in V8.6.3
+----------------------
+
+- Small memory leaks in Region  and FitsChan classes have been fixed.
+
+-  A bug that could cause an internal buffer overrun within the FitsChan
+class when writing out a FITS-WCS spectral axis with the "-LOG" algorithm
+has been fixed.
+
+- The test that a Mapping conforms to the requirements of the SIP FITS
+distortion scheme has been improved.
+
+- The astRebinSeq method of the Mapping class can now use a different
+weight when pasting each separate input data array into the output mosaic.
+
+Main Changes in V8.6.2
+----------------------
+
+- The astWrite method of the FitsChan class can now create FITS-WCS headers
+that include keyords describing focal plane distortion using the
+conventions of the Spitzer SIP scheme. This is however only possible if
+the SipOK attribute of the FitsChan is set to a non-zero value (which is
+the default), and the FrameSet being written out contains an appropriate
+PolyMap that conforms to the requirements of the SIP convention.
+
+- The behaviour of the astLinearApprox method of the Mapping class has
+been changed in cases where the Mapping being approximated generates bad
+(AST__BAD) values for one or more of its outputs. Previously, any such
+Mapping would be deemed non-linear and no fit would be returned. Now, a
+fit is returned, provided the other outputs of the Mapping are linear,
+but the fit contains AST__BAD values for the coefficients describing the
+bad Mapping output.
+
+- The astRebinSeq<X> functions accepts a new flag, AST__PARWGT, which
+allows the initial weight to be given for the data being pasted into the
+output arrays (the initial weight to use should be include in the "params"
+array). This initial weight defaults to 1.0 if the AST__PARWGT flag is not
+given.
+
+Main Changes in V8.6.1
+----------------------
+
+- A new function call astCreatedAt is now available that returns the function
+name, file path and line number at which an AST object was first created.
+
+- The number of digits used to format floating point values has been
+increased in order to avoid loss of precision when converting from binary
+to string and back to binary. This could cause very small changes in numerical
+values returned by AST functions.
+
+- If a FrameSet is supplied as the "Map" argument to astAddFrame, it now
+extracts and stores the base->current Mapping from the supplied FrameSet.
+Previously, the entire FrameSet was stored as the Mapping.
+
+
+Main Changes in V8.5.1
+----------------------
+
+- A new class of Mapping called ChebyMap has been added. This is a
+Mapping that implements Chebyshev polynomial transformations.
+
+- If the function that delivers error messages to the user (astPutErr) is
+re-implemented, the new version can now be registered at run-time using
+the new astSetPutErr function. Previously, the new version needed to be
+linked into the application at build time.
+
+- A bug has been fixed in the PolyMap class that caused incorrect values
+to be returned for the TranForward and TranInverse attributes if the PolyMap
+has been inverted.
+
+- The KeyMap class has a new method called astMapGetC (AST_MAPGETC) which
+returns a named entry as a single string. If the entry is a vector the
+returned string is a comma-separated list of its elements, enclosed in
+parentheses.
+
+- The Frame class now has a new attribute caled DTAI, which can be used
+to specify the number of leap seconds at the moment represented by the
+Frame's Epoch attribute. By default, the internal look-up table of leap
+seconds contained within AST is used. The DTAI attribute allows old
+versions of AST, which may not include the most recent leap seconds, to
+be used with new data.
+
+- The TimeMap class has been changed so that some conversions now require
+a "Dtai" value (i.e. the number of leap seconds) to be supplied by the
+caller. If AST__BAD is supplied for "Dtai", the internal look-up table of
+leap seconds contained withn AST will be used. The conversions affected
+are those between TAI and UTC, and those between TT and TDB.
+
+Main Changes in V8.3.0
+----------------------
+
+- The PAL library files included in the AST distribution have been updated
+to PAL version 0.9.7.
+
+- Multiple identical NormMaps in series will now be simplified to a
+single NormMap.
+
+- A NormMap that encapsulates a basic Frame will now be simplified to a
+UnitMap.
+
+- The astTimeAdd (AST_TIMEADD) method of the TimeMap class now include an
+extra argument that gives the number of values supplied in the arguments
+array. Note, any existing code that uses this method will need to be
+changed.
+
+- The astSlaAdd (AST_SLAADD) method of the SlaMap class now include an
+extra argument that gives the number of values supplied in the arguments
+array. Note, any existing code that uses this method will need to be
+changed.
+
+- The astSpecAdd (AST_SPECADD) method of the SpecMap class now include an
+extra argument that gives the number of values supplied in the arguments
+array. Note, any existing code that uses this method will need to be
+changed.
+
+- If the astMapRegion (AST_MAPREGION) method is used to map a Region into
+a new Frame that has fewer axes than the original Region, and if the
+inverse transformation of the supplied Mapping does not specify a value
+for the missing axes, then those axes are removed entirely from the
+Region. Previously they were retained, but supplied with bad values. This
+affects the number of mesh points per axes for such Regions, and so
+affects the accuracy of overlap determination.
+
+
+Main Changes in V8.3.0
+----------------------
+
+- A new method called astAxNorm has been added to the Frame class that
+normalises an array of axis values. When used with SkyFrames, it allows
+longitude values to be normalised into the shortest range.
+
+- A bug has been fixed in the Fortran include file AST_PAR that caused constants
+related to PI to be defined as single rather than double precision.
+
+- A bug has been fixed in the astGetRegionBounds method that could
+cause the wrong bounds to be returned for regions spanning a longitude =
+zero singularity.
+
+Main Changes in V8.2.0
+----------------------
+
+- A new class of Mapping called UnitNormMap has been added that converts a
+vector to a unit vector relative to a specified centre, plus length. A
+UnitNormMap has N inputs and N+1 outputs.The lower N output coordinates
+represent a unit vector parallel to the supplied input vector, and the
+(N+1)'th output coordinate is the length of the input vector.
+
+- The restriction that Mappings are immutable has been extended to all
+Mapping classes. This means that attributes representing parameters of
+a Mapping's forward or inverse transformation cannot be changed after
+the Mapping has been created. In order to minimise the risk to existing
+software, this rule does not apply to Mappings that have not yet been
+included in other objects such as CmpMaps or FrameSets, or which have not
+yet been cloned. In other words, an error is reported if an attempt is
+made to change the nature of a Mapping's transformation, but only if the
+reference count of the Mapping is greater than one. The Mapping classes
+affected include: GrismMap, LutMap, PcdMap, SphMap, WcsMap and ZoomMap.
+
+
+Main Changes in V8.1.0
+----------------------
+
+- The configure script has a new option "--without-fortran" that allows
+AST to be built in situations where no Fortran compiler is available. The
+resulting library has no Fortran interface and so cannot be used within
+Fortran applications. Also, the link scripts do not attempt to include the
+fortran runtime libraries.
+
+Main Changes in V8.0.7
+----------------------
+
+- A bug in FitsChan has been fixed which could cause a small shift in
+  spectral axis value when writing out a spectral cube to FITS-WCS headers,
+  This shift occurred only if the celestial axes in the cube were not FK5
+  (RA,Dec).
+
+- Avoid some more compiler warnings.
+
+- A "BadKeyValue" warning is now issued by the FitsChan class if an illegal
+FITS keyword value is encountered. See attribute "Warnings" and function
+"astWarnings".
+
+Main Changes in V8.0.6
+----------------------
+
+- Fix bug in FitsChan that caused SIP headers to be treated as linear
+when creating a FrameSet from the headers.
+
+- Fix bug in LutMap that incorrectly allowed an inverse lutmap to be used
+even if the original LutMap was not monotonic.
+
+- Allow attributes to be set for each plane of a Plot3D.
+
+- Avoid some compiler warnings.
+
+Main Changes in V8.0.5
+----------------------
+
+- The SkyFrame class has a new attribute called SkyTol, which specifies
+the smallest significant distance within the SkyFrame. It is used to
+decide if the Mapping between two SkyFrames can be considered a unit
+transformation. The default value is 0.001 arc-seconds.
+
+- A bug has been fixed in the FitsChan class that prevented illegal
+characters within FITS keyword names (i.e. characters not allowed by the
+FITS standard) being detected. This bug could under some circumstances
+cause a subsequent segmentation violation to occur.
+
+- A "BadKeyName" warning is now issued by the FitsChan class if a FITS
+keyword name is encountered that contains any illegal characters. See
+attribute "Warnings" and function "astWarnings".
+
+Main Changes in V8.0.4
+----------------------
+
+- The behaviour of the astAddFrame method has been changed slightly.
+Previously, astAddFrame modified the FrameSet by storing references to
+the supplied Mapping and Frame objects within the FrameSet. This meant
+that any subsequent changes to the current Frame of the modified FrameSet
+also affected the supplied Frame object. Now, astAddFrame stores deep
+copies of the Mapping and Frame objects (rather than references) within
+the modified FrameSet. This means that subsequent changes to the modified
+FrameSet will now have no effect on the supplied Frame.
+
+- The choice of default tick-mark for time axes has been improved, to avoid
+previous issues which could result in no suitable gap being found, or
+inappropriate tick marks when using formatted dates.
+
+- A new method called astRegionOutline has been added to the Plot class.
+It draws the outline of a supplied AST Region.
+
+- A bug has been fixed that could cause astSimplfy to enter an infinite loop.
+
+- Some improvements have been made to the Mapping simplification process
+that allow more Mappings to be simplified.
+
+- The Frame class has a new read-only attribute called "InternalUnit",
+which gives the units used for the unformatted (i.e. floating-point) axis
+values used internally by application code. For most Frames, the
+InternalUnit value is just the same as the Unit value (i.e. formatted and
+unformatted axis values use the same units). However, the SkyFrame class
+always returns "rad" for InternalUnit, regardless of the value of Unit,
+indicating that floating-point SkyFrame axis values are always in units
+of radians.
+
+- The LutMap class has a new attribute called LutEpsilon, which specifies
+the relative error of the values in the table. It is used to decide if
+the LutMap can be simplified to a straight line.
+
+
+Main Changes in V8.0.3
+----------------------
+
+- Methods astRebin, astRebinSeq, astResample and astTranGrid now report an
+error if an array is specified that has more pixels than can be counted by
+a 32 bit integer.
+
+- The hypertext documentation is now generated using Tex4HT rather
+than latex2html. The format of the hypertext docs has changed
+significantly.
+
+- Another bug fix associated with reading CAR projections from FITS-WCS headers.
+
+- Constructor options strings of the form "..., "%s", text );" can now be
+supplied. This avoids a security issue associated with the alternative
+form "..., text );".
+
+
+Main Changes in V8.0.2
+----------------------
+
+- For security reasons, the change introduced to astAppendString in
+  V8.0.1 has been moved to a new function called astAppendStringf, and
+  astAppendString itself has been reverted to its V8.0.0 version.
+
+
+Main Changes in V8.0.1
+----------------------
+
+- The macro used to invoke the astAppendString utility function has
+  changed to allow printf-style converstions to be included in the
+  supplied text. Any code that uses this macro must be re-compiled.
+
+- The astRebin and astRebinSeq family of functions now include support
+  for arrays with char (byte) and unsigned char (unsigned byte) data types.
+
+- The Base and Current attributes of a FrameSet may now be set using the
+  Domain name or the index of the required Frame.
+
+- The FITS XPH projection is now supported.
+
+- The order of WCS axes within new FITS-WCS headers created by astWrite
+  can now be controlled using a new attribute called FitsAxisOrder.
+
+Main Changes in V8.0.0
+----------------------
+
+- AST is now distributed under the Lesser GPL licence.
+
+- Least squares fitting of N-dimensional polynomials is now done using
+files copied from the C/C++ Minpack package (see
+http://devernay.free.fr/hacks/cminpack/index.html).
+
+- Use of the IAU SOFA library has been replaced by ERFA library, which is
+a re-badged copy of SOFA distributed under a less restrictive license. A
+copy of ERFA is included within AST.
+
+Main Changes in V7.3.4
+----------------------
+
+- By default, the simplification of Polygons no longer checks that the
+edges are not bent by the simplification. A new attribute, SimpVertices,
+can be set to zero in order to re-instate this check.
+
+- The Polygon class has a new mathod, astConvex, that returns a Polygon
+representing the shortest polygon (i.e. convex hull) enclosing a
+specified set of pixel values within a supplied array.
+
+Main Changes in V7.3.3
+----------------------
+
+- The FitsChan class has new attributes CardName and CardComm, which hold
+the keyword name and comment of the current card.
+
+- When reading FITS-WCS headers that include polynomial distortion in the
+SIP format, any inverse transformation specified in the header is now
+ignored and a new inverse is created to replace it based on the supplied
+forward transformation. Previously, an inverse was created only if the
+header did not include an inverse. The accuracy of the inverse
+transformation has also been improved, although it may now be slower to
+evaluate in some circumstances.
+
+- A bug has been fixed that could over-write the FitsChan CarLin attribute
+with a non-zero value if the header contains a spectral axis.
+
+- The default options for each newly created FitsChan can now be
+specified via the environment variable FITSCHAN_OPTIONS.
+
+Main Changes in V7.3.2
+----------------------
+
+- Fix support for reading GLS projections from FITS headers.
+
+- The KeyMap class has new sorting options "KeyAgeUp" and "KeyAgeDown" that
+retain the position of an existing entry if its value is changed. See the
+SortBy attribute.
+
+- A bug has been fixed in FitsChan that caused CDELT keywords for sky
+axes to be treated as radians rather than degrees when reading a FITS
+header, if the corresponding CTYPE values included no projection code.
+
+
+Main Changes in V7.3.1
+----------------------
+
+- Fix bug that could cause a segmenatation fault when reading a FITS TNX
+header.
+
+Main Changes in V7.3.0
+----------------------
+
+- IMPORTANT! The interface for the astRebinSeq<X> (AST_REBINSEQ) family
+of functions has been changed in order to allow a greater number of
+pixels to be pasted into the output array. In C, the "nused" parameter
+is now a pointer to a "int64_t" variable, instead of a simple "int". In
+Fortran, the NUSED argument for AST_REBINSEQ<X> is now an INTEGER*8.
+
+APPLICATION CODE SHOULD BE CHANGED ACCORDINGLY TO AVOID SEGMENTATION
+FAULTS AND OTHER ERRATIC BEHAVIOUR.
+
+- Added a new facility to the FrameSet class to allow each Frame to be
+associated with multiple Mappings, any one of which can be used to
+connect the Frame to the other Frames in the FrameSet. The choice of
+which Mapping to use is controlled by the new "Variant" attribute of the
+FrameSet class.
+
+- Mappings (but not Frames) that have a value set for their Ident attribute
+are now left unchanged by the astSimplify (AST_SIMPLIFY) function.
+
+Main Changes in V7.2.0
+----------------------
+
+- A new method call astMapDefined has been added to the KeyMap class.
+It checks if a gtiven key name has a defined value in a given KeyMap.
+
+
+Main Changes in V7.1.1
+----------------------
+
+- A bug has been fixed in FitsChan that caused inappropriate CTYPE values
+to be generated when writing a FrameSet to FITS-WCS headers if the
+current Frame describes generalised spherical coordinates (i.e. a
+SkyFrame with System=Unknown).
+
+- When a FitsChan is used to write an "offset" SkyFrame (see attribute
+SkyRefIs) to a FITS-WCS encoded header, two alternate axis descriptions
+are now created - one for the offset coordinates and one for the absolute
+coordinates. If such a header is subsequently read back into AST, the
+original offset SkyFrame is recreated.
+
+
+Main Changes in V7.1.0
+----------------------
+
+- IMPORTANT! The default behaviour of astRebinSeq is now NOT to conserve
+flux. To conserve flux, the AST__CONSERVEFLUX flag should be supplied
+when calling astRebinSeq. Without this flag, each output value is a
+weighted mean of the neighbouring input values.
+
+- A new flag AST__NONORM can be used with astRebinSeq<X> to indicate that
+normalisation of the output arrays is not required. In this case no
+weights array need be supplied.
+
+- A bug has been fixed in astAddFrame (AST_ADDFRAME) method that could
+result in the incorrect inversion of Mappings within the FrameSet when
+the AST__ALLFRAMES flag is supplied for the "iframe" parameter.
+
+- The astRate method has been re-written to make it faster and more
+reliable.
+
+Main Changes in V7.0.6
+----------------------
+
+- A bug has been fixed in astRebinSeq<X> which could result in
+incorrect normalisation of the final binned data and variance values.
+
+- When reading a FrameSet from a FITS-DSS header, the keywords CNPIX1 and
+CNPIX2 now default to zero if absent. Previously an error was reported.
+
+Main Changes in V7.0.5
+----------------------
+
+- The FitsChan class can now read FITS headers that use the SAO
+convention for representing distorted TAN projections, based on the use
+of "COi_j" keywords to hold the coefficients of the distortion polynomial.
+
+
+Main Changes in V7.0.4
+----------------------
+
+- The previously private grf3d.h header file is now installed into
+prefix/include.
+
+
+Main Changes in V7.0.3
+----------------------
+
+- A bug has been fixed which could cause an incorrect axis to be used when
+accessing axis attributes within CmpFrames. This could happen if axes
+within the CmpFrame have been permuted.
+
+- A bug has been fixed in the SkyFrame class that could cause the two
+values of the SkyRef and/or SkyRefP attributes to be reversed.
+
+- Bugs have been fixed in the CmpRegion class that should allow the border
+around a compound Region to be plotted more quickly, and more accurately.
+Previously, component Regions nested deeply inside a CmpRegion may have
+been completely or partially ignored.
+
+- A bug has been fixed in the Plot3D class that caused a segmentation
+violation if the MinTick attribute was set to zero.
+
+- The astResampleX set of methods now includes astResampleK and
+astResampleUK that handles 64 bit integer data.
+
+Main Changes in V7.0.2
+----------------------
+
+- The libast_pal library is no longer built if the "--with-external_pal"
+option is used when AST is configured.
+
+
+Main Changes in V7.0.1
+----------------------
+
+- The levmar and wcslib code distributed within AST is now stored in the
+main AST library (libast.so) rather than in separate libraries.
+
+
+Main Changes in V7.0.0
+----------------------
+
+- Fundamental positional astronomy calculations are now performed
+using the IAU SOFA library where possible, and the Starlink PAL library
+otherwise (the PAL library contains a subset of the Fortran Starlink SLALIB
+library re-written in C). Copies of these libraries are bundled with AST
+and so do not need to be obtained or built separately, although external
+copies of SOFA and PAL can be used if necessary by including the
+"--with-external_pal" option when configuring AST.
+
+
+Main Changes in V6.0-1
+-----------------------
+
+- The Spitzer "-SIP" distortion code is now recognised within FITS
+headers that describe non-celestial axes, as well as celestial axes.
+
+- A bug has been fixed that could cause inappropriate equinox values to
+be used when aligning SkyFrames if the AlignSystem attribute is set.
+
+- The format of the version string for AST has changed from
+"<major>.<minor>-<release>" to "<major>.<minor>.<release>".
+
+Main Changes in V6.0
+-----------------------
+
+- This version of AST is the first that can be used with the Python
+AST wrapper module, starlink.Ast, available at http://github.com/timj/starlink-pyast.
+
+- When reading a FITS-WCS header, the FitsChan class now recognises the
+non-standard "TPV" projection code within a CTYPE keyword value. This
+code is used by SCAMP (see www.astromatic.net/software/scamp) to
+represent a distorted TAN projection.
+
+- The Plot class has been changed to remove visual anomalies (such as
+incorrectly rotated numerical axis labels) if the graphics coordinates have
+unequal scales on the X and Y axes.
+
+- The graphics escape sequences used to produce graphical sky axis labels
+can now be changed using the new function astTuneC (AST_TUNEC).
+
+Main Changes in V5.7-2
+-----------------------
+
+- The PolyMap class can now use an iterative Newton-Raphson method to
+evaluate the inverse the inverse transformation if no inverse
+transformation is defined when the PolyMap is created.
+
+- The FitsChan class has a new method astWriteFits (AST_WRITEFITS)
+which writes out all cards currently in the FitsChan to the associated
+external data sink (specified either by the SinkFile attribute or the
+sink function supplied when the FitsChan was created), and then empties
+the FitsChan.
+
+- The FitsChan class has a new method astReadFits (AST_READFITS)
+which forces the FitsChan to reads cards from the associated external
+source and appends them to the end of the FitsChan.
+
+- The FitsChan class has a new read-only attribute called "Nkey", which
+holds the number of keywords for which values are held in a FitsChan.
+
+- The FitsChan class has a new read-only attribute called "CardType", which
+holds the data type of the keyword value for the current card.
+
+- The FitsChan astGetFits<X> (AST_GETFITS<X>) methods can now be used to
+returned the value of the current card.
+
+- If the FitsChan astRead method reads a FITS header that uses the
+-SIP (Spitzer) distortion code within the CTYPE values, but which does
+not provide an inverse polynomial correction, and for which the PolyTran
+method of the PolyMap class fails to create an accurate estimate of the
+inverse polynomial correction, then an iterative method will be used to
+evaluate the inverse correction for each point transformed.
+
+- The Object class has a new function astToString (C only), which creates
+an in-memory textual serialisation of a given AST Object. A corresponding
+new function called astFromString re-creates the Object from its
+serialisation.
+
+
+Main Changes in V5.7-1
+-----------------------
+
+- All classes of Channel can now read to and write from specified text
+files, without the need to provide source and sink functions when the
+Channel is created. The files to use are specified by the new attributes
+SourceFile and SinkFile.
+
+- The FitsChan class now ignores trailing spaces in character-valued WCS
+keywords when reading a FrameSet from a FITS header.
+
+- If the FitsChan astRead method reads a FITS header that uses the -SIP
+(Spitzer) distortion code within the CTYPE values, but which does not
+provide an inverse polynomial correction, the FitsChan class will now use
+the PolyTran method of the PolyMap class to create an estimate of the
+inverse polynomial correction.
+
+
+
+Main Changes in V5.7-0
+-----------------------
+
+- The FitsChan class support for the IRAF-specific "TNX" projection has
+been extended to include reading TNX headers that use a Chebyshev
+representation for the distortion polynomial.
+
+- The FitsChan class support for the IRAF-specific "ZPX" projection has
+been extended to include reading ZPX headers that use simple or Chebyshev
+representation for the distortion polynomial.
+
+- A bug has been fixed in the FitsChan class that caused headers
+including the Spitzer "-SIP" distortion code to be read incorrectly if no
+inverse polynomial was specified in the header.
+
+- A new attribute called PolyTan has been added to the FitsChan class. It
+can be used to indicate that FITS headers that specify a TAN projection
+should be interpreted according to the "distorted TAN" convention
+included in an early draft of FITS-WCS paper II. Such headers are created
+by (for instance) the SCAMP tool (http://www.astromatic.net/software/scamp).
+
+- The PolyMap class now provides a method called astPolyTran (AST_POLYTRAN)
+that adds an inverse transformation to a PolyMap by sampling the forward
+transformation on a regular grid, and then fitting a polynomial function
+from the resulting output values to the grid of input values.
+
+
+Main Changes in V5.6-1
+-----------------------
+
+- Tables can now have any number of parameters describing the global
+properties of the Table.
+
+- Frames now interpret the unit string "A" as meaning "Ampere" rather
+than "Angstrom", as specified by FITS-WCS paper I.
+
+- A bug has been fixed in the astFindFrame (AST_FINDFRAME) method that
+allowed a template Frame of a more specialised class to match a target
+frame of a less specialised class. For example, this bug would allow a
+template SkyFrame to match a target Frame. This no longer happens.
+
+
+Main Changes in V5.6-0
+-----------------------
+
+- New functions astBBuf (AST_BBUF) and astEBuf (AST_EBUF) have been added
+to the Plot class. These control the buffering of graphical output
+produced by other Plot methods.
+
+- New functions astGBBuf and astGEBuf have been added to the interface
+defined by file grf.h. The ast_link command has been modified so that the
+-grf_v3.2 switch loads dummy versions of the new grf functions. This
+means that applications that use the -grf_v3.2 switch should continue to
+build without any change. However, the new public functions astBBuf and
+astEBuf described in the previous item will report an error unless the
+new grf functions are implemented. If you choose to implement them, you
+should modify your linking procedure to use the -grf (or -grf_v5.6)
+switch in place of the older -grf_v3.2 switch. See the description of the
+ast_link command for details of these switches.
+
+- New method astGetRegionMesh (AST_GETREGIONMESH) returns a set of
+positions covering the boundary, or volume, of a supplied Region.
+
+Main Changes in V5.5-0
+-----------------------
+
+- The FitsChan "TabOK" attribute is now an integer value rather
+than a boolean value. As in previous versions, it is used to indicate
+whether the "-TAB" algorithm should be supported by the astRead
+(AST_READ) and astWrite (AST_WRITE) methods, but in addition it is now
+also used to give the version number to assign to any table gebnerated as
+a consequence of calling astWrite (AST_WRITE).  A negative or zero value
+(the default) indicates that support for the -TAB algorithm is not
+available, where as a positive non-zero value indicates that support is
+available and also gives the table version number to use when creating
+subsequent -TAB headers.
+
+
+Main Changes in V5.4-0
+-----------------------
+
+- The FitsChan class now has an option to support reading and writing
+of FITS-WCS headers that use the -TAB algorithm described in FITS-WCS paper
+III. This option is controlled by a new FitsChan attribute called TabOK.
+See the documentation for TabOK for more information.
+
+- A new class called "Table" has been added. A Table is a KeyMap in
+which each entry represents a cell in a two-dimensional table.
+
+- A new class called "FitsTable" has been added. A FitsTable is a
+Table that has an associated FitsChan holding headers appropriate to a
+FITS binary table.
+
+- KeyMaps can now hold byte (i.e. "unsigned char" or BYTE) values.
+
+- A new method called astMapRename (AST_MAPRENAME) has been added to rename
+an existing entry in a KeyMap.
+
+- KeyMaps have a new attribute called KeyCase that can be set to zero to
+make the handling of keys case insensitive.
+
+Main Changes in V5.3-2
+-----------------------
+
+- A bug has been fixed in the FitsChan class that could cause wavelength
+axes to be assigned the units "m/s" when reading WCS information from a
+FITS header.
+
+- The astSet function (AST_SET) now allows literal commas to be included in
+string attribute values. String attribute values that include a literal
+comma should be enclosed in quotation marks.
+
+- A bug in FitsChan has been fixed that caused "-SIN" projection codes within
+FITS-WCS headers to be mis-interpreted, resulting in no FrameSet being
+read by astRead.
+
+- The KeyMap class has a new attribute called "SortBy". It controls
+the order in which keys are returned by the astMapKey (AST_MAPKEY) function.
+Keys can be sorted alphabetically or by age, or left unsorted.
+
+- Access to KeyMaps holding thousands of entries is now significantly
+faster.
+
+- KeyMaps can now hold word (i.e. "short int" or INTEGER*2) values.
+
+Main Changes in V5.3-1
+-----------------------
+
+- The KeyMap class has a new method called astMapCopy/AST_MAPCOPY that
+copies entries from one KeyMap to another KeyMap.
+
+- The KeyMap class now supports entries that have undefined values. A
+new method called astMapPutU/AST_MAPPUTU will store an entry with undefined
+value in a keymap.
+
+- The KeyMap class has a new boolean attribute called MapLocked. If true
+(non-zero), an error is reported if an attempt is made to add any new entries
+to a KeyMap (the value associated with any old entry may still be changed #
+without error). The default is false (zero).
+
+- The Object class has a new method called astHasAttribute/AST_HASATTRIBUTE
+that returns a boolean value indicating if a specified Object has a named
+attribute.
+
+- The SkyFrame class has two new read-only boolean attributes called
+IsLatAxis and IsLonAxis that can be used to determine the nature of a
+specified SkyFrame axis.
+
+- A bug has been fixed in the astRebin(Seq)/AST_REBIN(SEQ) methods
+that could cause flux to be lost from the edges of the supplied array.
+
+- A bug has been fixed in the astRebin(Seq)/AST_REBIN(SEQ) methods
+that caused the first user supplied parameter to be interpreted as the
+full width of the spreading kernel, rather than the half-width.
+
+- The StcsChan class now ignores case when reading STC-S phrases (except
+that units strings are still case sensitive).
+
+- The Channel class now has an Indent attribute that controls indentation
+in the text created by astWrite/AST_WRITE. The StcsIndent and XmlIndent
+attributes have been removed.
+
+- All classes of Channel now use the string "<bad>" to represent the
+floating point value AST__BAD, rather than the literal formatted value
+(typically "-1.79769313486232e+308" ).
+
+- The KeyMap class now uses the string "<bad>" to represent the
+floating point value AST__BAD, rather than the literal formatted value
+(typically "-1.79769313486232e+308" ).
+
+- The KeyMap class has a new method called astMapPutElem<X>/AST_MAPPUTELEM<X>
+that allows a value to be put into a single element of a vector entry in
+a KeyMap. The vector entry is extended automatically to hold the new
+element if required.
+
+- The DSBSpecFrame class now reports an error if the local oscillator
+frequency is less than the absoliute value of the intermediate frequency.
+
+- A new method astQuadApprox produces a quadratic fit to a 2D Mapping.
+
+- A new method astSkyOffsetMap produces a Mapping from absolute SkyFrame
+coordinates to offset SkyFrame coordinates.
+
+
+Main Changes in Version 5.3
+---------------------------
+
+- The details of how a Frame is aligned with another Frame by the
+astFindFrame and astConvert (AST_FINDFRAME and AST_CONVERT) functions
+have been changed. The changes mean that a Frame can now be aligned with
+an instance of a sub-class of Frame, so long as the number of axes and
+the Domain values are consistent. For instance, a basic 2-dimensional
+Frame with Domain "SKY" will now align succesfully with a SkyFrame,
+conversion between the two Frames being achieved using a UnitMap.
+
+- The arrays that supply input values to astMapPut1<X> are now declared
+"const".
+
+- Added method astMatchAxes (AST_MATCHAXES) to the Frame class. This
+allows corresponding axes in two Frames to be identified.
+
+- The astAddFrame (AST_ADDFRAME) method can now be used to append one or
+more axes to all Frames in a FrameSet.
+
+
+Main Changes in Version 5.1
+---------------------------
+
+- A new method called astSetFitsCM (AST_SETFITSCM) has been added to
+the FitsChan class. It stores a pure comment card in a FitsChan (that
+is, a card with no keyword name or equals sign).
+
+- A new attribute called ObsAlt has been added to the Frame class. It
+records the geodetic altitude of the observer, in metres. It defaults to
+zero. It is used when converting times to or from the TDB timescale, or
+converting spectral positions to or from the topocentric rest frame, or
+converting sky positions to or from horizon coordinates. The FitsChan
+class will include its effect when creating a set of values for the
+OBSGEO-X/Y/Z keywords, and will also assign a value to it when reading a
+set of OBSGEO-X/Y/Z keyword values from a FITS header.
+
+- The TimeMap conversions "TTTOTDB" and "TDBTOTT", and the SpecMap
+conversions "TPF2HL" and "HLF2TP", now have an additional argument -
+the observer's geodetic altitude.
+
+- The Polygon class has been modified to make it consistent with the
+IVOA STC definition of a Polygon. Specifically, the inside of a polygon
+is now the area to the left of each edge as the vertices are traversed in
+an anti-clockwise manner, as seen from the inside of the celestial sphere.
+Previously, AST used the anti-clockwise convention, but viewed from the
+outside of the celestial sphere instead of the inside. Any Polygon saved
+using previous versions of AST will be identified and negated automatically
+when read by AST V5.2.
+
+- A new class of Channel, called StcsChan, has been added that allows
+conversion of suitable AST Objects to and from IVOA STC-S format.
+
+- A new method called astDownsize (AST_DOWNSIZE) has been added to the
+Polygon class. It produces a new Polygon that contains a subset of the
+vertices in the supplied Polygon. The subset is chosen to retain the main
+features of the supplied Polygion, in so far as that is possible, within
+specified constraints.
+
+- A new constructor called astOutline (AST_OUTLINE) has been added to the
+Polygon class. Given a 2D data array, it identifies the boundary of a
+region within the array that holds pixels with specified values. It then
+creates a new Polygon to describe this boundary to a specified accuracy.
+
+- A new method called astRemoveRegions (AST_REMOVEREGIONS) has been added
+to the Mapping class. It removes the masking effects of any Regions found
+within a (possibly compound) Mapping or Frame. In effect, it replaces
+each Region found within the Mapping or Frame with a UnitMap or
+equivalent Frame.
+
+- A new set of methods, called astMapGetElem<X> (AST_MAPGETELEM<X>) has
+been added to the KeyMap class. They allow a single element of a vector
+valued entry to be returned.
+
+- A new attribute called KeyError has been added to the KeyMap Class. It
+controls whether the astMapGet... (AST_MAPGET...) family of functions report
+an error if an entry with the requested key does not exist in the KeyMap.
+
+Main Changes in Version 5.1
+---------------------------
+
+- The astUnlock function now has an extra parameter that controls whether
+or not an error is reported if the Object is currently locked by another
+thread.
+
+- The values of the AST__THREADSAFE macro (defined in ast.h) have
+been changed from "yes" and "no" to "1" and "0".
+
+- The PointList class has a new method, astPoints, that copies the axis
+values from the PointList into a supplied array.
+
+- The PointList class has a new (read-only) attribute, ListSize, that
+gives the number of points stored in the PointList.
+
+- A new method (astIntersect) has been added to the Frame class. It
+determines the position at which two geodesic curves intersect.
+
+- The XmlStrict attribute and astXmlWarnings function have been removed.
+The same functionality is now available via the existing Strict attribute,
+a new attribute called ReportLevel, and a new function called astWarnings.
+
+- A bug in the type-checking of Objects passed as arguments to constructor
+functions has been fixed. This bug could lead to applications crashing or
+showing strange behaviour if an inappropriate class of Object was
+supplied as an argument to a constructor.
+
+- The astPickAxes function will now return a Region, if possible, when
+applied to a Region. If this is not possible, a Frame will be returned as
+before.
+
+- The default gap size between the ISO date/time labels used by the Plot
+class when displaying an annotated axis described by a TimeFrame has been
+changed. The changes are meant to improve the labelling of calendar time
+axes that span intervals from a day to a few years.
+
+Main Changes in Version 5.0
+---------------------------
+
+-  AST is now thread-safe. Many of the macro definitions in the "ast.h"
+header file have changed, and so all source code that include "ast.h"
+should be re-compiled.
+
+-  The TimeFrame class now support Local Time as a time scale. The offset
+from UTC to Local Time is specified by a new TimeFrame attribute called
+LTOffset.
+
+-  Addition of a new class called Plot3D that provides facilities for
+producing 3-dimensional annotated coordinate grids.
+
+-  A correction for diurnal aberration is now included when
+converting between AZEL and other celestial coordinate systems. The
+correction is based on the value of the ObsLat Frame attribute (the
+geodetic latitude of the observer).
+
+-  A bug has been fixed which caused the DUT1 attribute to be ignored
+by the SkyFrame class when finding conversions between AZEL and other
+celestial coordinate systems.
+
+-  The Channel class has a new attribute called Strict which controls
+whether or not to report an error if unexpected data items are found
+within an AST Object description read from an external data source. Note,
+the default behaviour is now not to report such errors. This differs from
+previous versions of AST which always reported an error is unexpected
+input items were encountered.
+
+
+
+Main Changes in Version 4.5
+---------------------------
+
+- All FITS-CLASS headers are now created with a frequency axis. If the
+FrameSet supplied to astWrite contains a velocity axis (or any other form
+of spectral axis) it will be converted to an equivalent frequency axis
+before being used to create the FITS-CLASS header.
+
+- The value stored in the FITS-CLASS keyword "VELO-LSR" has been changed
+from the velocity of the source to the velocity of the reference channel.
+
+- Addition of a new method call astPurgeWCS (AST_PURGEWCS) to the FitsChan
+class. This method removes all WCS-related header cards from a FitsChan.
+
+- The astRebinSeq functions now have an extra parameter that is used to
+record the total number of input data val;ues added into the output
+array. This is necessary to correct a flaw in the calculation of output
+variances based on the spread of input values. NOTE, THIS CHANGE WILL
+REQUIRE EXISTING CODE THAT USES ASTREBINSEQ TO BE MODIFIED TO INCLUDE THE
+NEW PARAMETER (CALLED "NUSED").
+- The Plot class now honours the value of the LabelUp attribute even if
+numerical labels are placed around the edge of the Plot. Previously
+LabelUp was only used if the labels were drawn within the interior of
+the plot. The LabelUp attribute controls whether numerical labels are
+drawn horizontally or parallel to the axis they describe.
+- The Plot class has a new attribute called GrfContext that can be used
+to comminicate context information between an application and any
+graphics functions registered with the Plot class via the astGrfSet
+(AST_GRFSET) function.
+- Functions registered with the Plot class using astGrfSet (AST_GRFSET)
+now take a new additional integer parameter, "grfcon". The Plot class
+sets this parameter to value of the Plot's GrfContext attribute before
+calling the graphics function. NOTE, THIS CHANGE WILL REQUIRE EXISTING
+CODE THAT USES astGrfSet (AST_GRFSET) TO BE MODIFIED TO INCLUDE THE
+NEW PARAMETER.
+-  Support has been added for the FITS-WCS "HPX" projection (HEALPix).
+-  A new flag "AST__VARWGT" can be supplied to astRebinSeq. This causes
+the input data values to be weighted using the reciprocals of the input
+variances (if supplied).
+- The Frame class has a new read-only attribute called NormUnit that
+returns the normalised value of the Unit attribute for an axis. Here,
+"normalisation" means cancelling redundant units, etc. So for instance, a
+Unit value of "s*(m/s)" would result in a NormUnit value of "m".
+- A new method astShowMesh has been added to the Region class. It
+displays a mesh of points covering the surface of a Region by writing out
+a table of axis values to standard output.
+- A bug has been fixed that could segmentation violations when setting
+attribute values.
+
+Main Changes in Version 4.4
+---------------------------
+
+- The astFindFrame (AST_FINDFRAME) method can now be used to search a
+CmpFrame for an instance of a more specialised class of Frame (SkyFrame,
+TimeFrame, SpecFrame, DSBSpecFrame or FluxFrame). That is, if an instance
+of one of these classes is used as the "template" when calling
+astFindFrame, and the "target" being searched is a CmpFrame (or a
+FrameSet in which the current Frame is a CmpFrame), then the component
+Frames within the CmpFrame will be searched for an instance of the
+supplied template Frame, and, if found, a suitable Mapping (which will
+include a PermMap to select the required axes from the CmpFrame) will be
+returned by astFindFrame. Note, for this to work, the MaxAxes and MinAxes
+attributes of the template Frame must be set so that they cover a range
+that includes the number of axes in the target CmpFrame.
+
+- The DSBSpecFrame class has a new attribute called AlignSB that
+specifies whether or not to take account of the SideBand attributes when
+aligning two DSBSpecFrames using astConvert (AST_CONVERT).
+
+- The Frame class has a new attribute called Dut1 that can be used to
+store a value for the difference between the UT1 and UTC timescales at
+the epoch referred to by the Frame.
+
+- The number of digits used to format the Frame attributes ObsLat and
+ObsLon has been increased.
+
+- The use of the SkyFrame attribute AlignOffset has been changed. This
+attribute is used to control how two SkyFrames are aligned by astConvert.
+If the template and target SkyFrames both have a non-zero value for
+AlignOffset, then alignment occurs within the offset coordinate systems
+(that is, a UnitMap will always be used to align the two SkyFrames).
+
+- The Plot class has a new attribute called ForceExterior that can be
+used to force exterior (rather than interior) tick marks to be produced,
+even if this would result in less than 3 tick marks being produced.
+
+- The TimeFrame class now supports conversion between angle based
+timescales such as UT1 and atomic based timescales such as UTC.
+
+
+Main Changes in Version 4.3
+---------------------------
+
+- The SpecFrame class has a new attribute called SourceSys that specified
+whether the SourceVel attribute (which specifies the rest frame of the
+source) should be accessed as an apparent radial velocity or a redshift.
+Note, any existing software that assumes that SourceVel always represents
+a velocity in km/s should be changed to allow for the possibility of
+SourceVel representing a redshift value.
+
+-  The astGetFitsS (AST_GETFITSS) function now strips trailing white space
+from the returned string, if the original string contains 8 or fewer
+characters.
+
+
+Main Changes in Version 4.2
+---------------------------
+
+- The SideBand attribute of the DSBSpecFrame class can now take the
+option "LO" in addition to "USB" and "LSB". The new option causes the
+DSBSpecFrame to represent the offset from the local oscillator frequency,
+rather than either of the two sidebands.
+
+- The FitsChan class has been changed so that it writes out a VELOSYS
+keyword when creating a FITS-WCS encoding (VELOSYS indicates the
+topocentric apparent velocity of the standard of rest). FitsChan also
+strips out VELOSYS keywords when reading a FrameSet from a FITS-WCS
+encoding.
+
+- The FitsChan class has a new method called astRetainFits (AST_RETAINFITS)
+that indicates that the current card in the FitsChan should not be
+stripped out of the FitsChan when an AST Object is read from the FitsChan.
+Unless this method is used, all cards that were involved in the creation
+of the AST Object will be stripped from the FitsChan afte a read operation.
+
+- The ast_link_adam and ast_link scripts now ignore the -fsla and -csla
+options, and always link against the minimal cut-down version of SLALIB
+distributed as part of AST.
+
+- A problem with unaligned memory access that could cause bus errors on
+Solaris has been fixed.
+
+- A new function called astTune (or AST_TUNE) has been added which can be
+used to get and set global AST tuning parameters. At the moment there are
+only two such parameter, both of which are concerned with memory management
+within AST.
+
+- A new method called astTranGrid (AST_TRANGRID in Fortran) has been
+added to the Mapping class. This method creates a regular grid of points
+covering a rectangular region within the input space of a Mapping, and
+then transforms this set of points into the output space of the Mapping,
+using a piecewise-continuous linear approximation to the Mapping if
+appropriate in order to achive higher speed.
+
+- A new subclass of Mapping has been added called SwitchMap. A
+SwitchMap represents several alternate Mappings, each of which is used to
+transforms input positions within a different region of the input
+coordinate space.
+
+- A new subclass of Mapping has been added called SelectorMap. A
+SelectorMap tests each input position to see if it falls within one of
+several Regions. If it does, the index of the Region containing the
+input position is returned as the Mapping output.
+
+- The behaviour of the astConvert (AST_CONVERT) method when trying to
+align a CmpFrame with another Frame has been modified. If no conversion
+between positions in the Frame and CmpFrame can be found, an attempt is
+now made to find a conversion between the Frame and one of two component
+Frames contained within the CmpFrame. Thus is should now be possible to
+align a SkyFrame with a CmpFrame containing a SkyFrame and a SpecFrame
+(for instance). The returned Mapping produces bad values for the extra
+axes (i.e. for the SpecFrame axis in the above example).
+
+Main Changes in Version 4.1
+---------------------------
+
+- A new control flag has been added to the AST_RESAMPLE<X>/astResample<X>
+functions which produces approximate flux conservation.
+
+- The SkyFrame class now supports a System value of "AZEL" corresponding
+to horizon (azimuth/elevation) coordinates.
+
+- The FitsChan class allows the non-standard strings "AZ--" and "EL--" to
+be used as axis types in FITS-WCS CTYPE keyword values.
+
+- The Frame class now has attributes ObsLon and ObsLat to specify
+the geodetic longitude and latitude of the observer.
+
+- The ClockLon and ClockLat attributes have been removed from the
+TimeFrame class. Likewise, the GeoLon and GeoLat attributes have been
+removed from the SpecFrame class. Both classes now use the ObsLon and
+ObsLat attributes of the parent Frame class instead. However, the old
+attribute names can be used as synonyms for ObsLat and ObsLon. Also,
+dumps created using the old scheme can be read succesfully by AST V4.1
+and converted to the new form.
+
+- A new function astMapSplit has been added to the Mapping class. This
+splits a Mapping into two component Mappings which, when combined in
+parallel, are equivalent to the original Mapping.
+
+- The default value for the SkyRefIs attribute has been changed from
+"Origin" to "Ignored". This means that if you want to use a SkyFrame
+to represent offsets from some origin position, you must now set the
+SkyRefIs attribute explicitly to either "Pole" or "Origin", in addition
+to assigning the required origin position to the SkyRef attribute.
+
+
+Main Changes in Version 4.0
+---------------------------
+
+- Experimental support for reading IVOA Space-Time-Coordinates (STC)
+descriptions using the XmlChan class has been added. Support is included
+for a subset of V1.20 of the draft STC specification.
+
+- A new set of methods (AST_REBIN<X>/astRebin<X>) has been added to
+the Mapping class. These are accurately flux-conserving alternatives to the
+existing AST_RESAMPLE<X>/astResample<X> methods.
+
+
+Main Changes in Version 3.7
+---------------------------
+
+- Support for time coordinate systems has been introduced throught the
+addition of two new classes, TimeFrame and TimeMap. The TimeFrame is a
+1-dimensional Frame which can be used to describe moments in time (either
+absolute or relative) in various systems (MJD, Julian Epoch, etc.) and
+referred to various time scales (TAI, UTC, UT1, GMST, etc). The TimeMap
+is a Mapping which can transform time values between these various
+systems and time scales.
+
+
+Main Changes in Version 3.6
+---------------------------
+
+- If the Format attribute associated with an axis of a SkyFrame starts
+with a percent character (%), then axis values are now formatted and
+unformatted as a decimal radians value, using the Format syntax of a
+simple Frame.
+
+- The Plot class has a new attribute called Clip which controls the
+clipping performed by AST at the plot boundary.
+
+- The PolyMap class has been modified to allow a PolyMap to be written
+succesfully to a FitsChan using Native encoding.
+
+- A mimimal cut down subset of the C version of SLALIB is now included
+with the AST distribution and built as part of building AST. This means
+that it is no longer necessary to have SLALIB installed separately at
+your site. The SLALIB code included with AST is distrubuted under the
+GPL. The default behaviour of the ast_link script is now to link with
+this internal slalib subset. However, the ``-csla'' option can still be
+used to force linking with an external full C SLALIB library. A new
+option ``-fsla'' has been introduced which forces linking with the
+external full Fortran SLALIB library.
+
+
+Main Changes in Version 3.5
+---------------------------
+
+- AST now provides facilities for representing regions of various
+shapes within a coordinate system. The Region class provides general
+facilities which are independent of the specific shape of region being
+used. Various sub-classes of Region are also now available which provide
+means of creating Regions of specific shape. Facilities provided by the
+Region class include testing points to see if they are inside the
+Region, testing two Regions for overlap, transforming Regions from one
+coordinate system to another, etc.
+
+- A new class of 1-dimensional Frame called FluxFrame has been added which
+can be used to describe various systems for describing ovserved value at a
+single fixed spectral position.
+
+- A new class of 2-dimensional Frame called SpecFluxFrame has been added which
+can be used to describe a 2-d frame spanned by a spectral position axis
+and and an observed value axis.
+
+- A new class of Mapping called RateMap has been added. A RateMap encapsulates
+a previously created Mapping. The inputs of the RateMap correspond to the
+inputs of the encapsulated Mapping. All RateMaps have just a single
+output which correspond to the rate of change of a specified output of
+the encapsulated Mapping with respect to a specified input.
+
+- The SkyFrame class now supports a value of "J2000" for System. This
+system is an equatorial system based on the mean dynamical equator and
+equinox at J2000, and differs slightly from an FK5(J2000) system.
+
+- Methods have been added to the FitsChan class to allow values for named
+keywords to be changed or added.
+
+- The parameter list for the astRate method of the Mapping class has been
+modified. It no longer returns a second derivative estimate. Existing
+code which uses the astRate (AST_RATE) method will need to be changed.