FITS Java library with WCS routines?

[David Berry]

On Fri, 4 Nov 2005 Neil.Killeen at csiro.au wrote:

> The Starlink AST library is comprehensive and offers more functionality
> than WCS (e.g. conversions between frames which WCS is not concerned
> with).

In general, handling coordinate system information involves more than
just transforming positions between pixel and WCS coords. Given that
FITS-WCS allows multiple alternate WCS frames, there is the question of
how you search all the available frames to see if a Frame can be found
with given characteristics, there is the question of what to do if you
want a pair of (RA,Dec) axes but the FITS header only contains galactic
latitude and longitude (in this case AST automatically identifies that a
conversion is possible and uses a built-in transformation). Given two WCS
headers, how do you determine the best way of aligning the corresponding
pixel grids? If you import a set of coordinate Frames from a FITS-WCS
header and then start manipulating the frame in complex ways (not just
simple linear operations), how do you keep track of the WCS? AST provides
a truly object oriented model for WCS which results in clean solutions to
all such WCS problems. It allows you to write general purpose code which
is independent of the specific coordinate systems being used.

In my experience of writing astronomical applications, remarkably few have
WCS requirements which stay within the bounds of simply transfoming
between pixel and WCS coords.

But it is true that AST provides things which not all applications will
need, like the plotting of annotated curvi-linear axes (which I believe
wcslib also provides), and support for reading, manipulating and
transforming STC instances. But these extras are obviously intimately tied
up with the handling of WCS information, and so it is not suprising that a
package such as AST provides them. If you *do* need these things then
having a uniform approach to all WCS-related tasks makes sense.


> However, it is also provided in C is it not, and Starlink is no longer
> funded.

Sadly the Starlink project is no longer funded, but I am now being funded
by JAC for work on SCUAB2 analysis software, for which AST is needed. Thus
I will still be maintaining AST (fixing bugs, etc), but development work
will obviously be much restricted.

David