Add a time coordinate conversion to a TimeMap


This routine adds one of the standard time coordinate system conversions listed below to an existing TimeMap.

When a TimeMap is first created (using AST_TIMEMAP), it simply performs a unit (null) Mapping. By using AST_TIMEADD (repeatedly if necessary), one or more coordinate conversion steps may then be added, which the TimeMap will perform in sequence. This allows multi-step conversions between a variety of time coordinate systems to be assembled out of the building blocks provided by this class.

Normally, if a TimeMap s Invert attribute is zero (the default), then its forward transformation is performed by carrying out each of the individual coordinate conversions specified by AST_TIMEADD in the order given (i.e. with the most recently added conversion applied last).

This order is reversed if the TimeMap s Invert attribute is non-zero (or if the inverse transformation is requested by any other means) and each individual coordinate conversion is also replaced by its own inverse. This process inverts the overall effect of the TimeMap. In this case, the first conversion to be applied would be the inverse of the one most recently added.




Pointer to the TimeMap.
CVT = CHARACTER ( ) (Given)
A character string which identifies the time coordinate conversion to be added to the TimeMap. See the " Available Conversions" section for details of those available.
The number of argument values supplied in the ARGS array.
An array containing argument values for the time coordinate conversion. The number of arguments required, and hence the number of array elements used, depends on the conversion specified (see the " Available Conversions" section). This array is ignored if no arguments are needed.
STATUS = INTEGER (Given and Returned)
The global status.


Available Conversions

The following strings (which are case-insensitive) may be supplied via the CVT argument to indicate which time coordinate conversion is to be added to the TimeMap. Where arguments are needed by the conversion, they are listed in parentheses. Values for these arguments should be given, via the ARGS array, in the order indicated. Units and argument names are described at the end of the list of conversions, and " MJD" means Modified Julian Date.

The units for the values processed by the above conversions are as follows:

The arguments used in the above conversions are the zero-points used by the AST_TRANSFORM routine. The axis values supplied and returned by AST_TRANSFORM are offsets away from these zero-points: