Open cdeil opened 6 years ago
@lmohrmann is adding CREF to the HESS FITS exporters now.
Does anyone have thoughts on CREF for IRFs? Maybe I should just go ahead and make a pull request for your review?
@cdeil The CREF
keywords is not currently listed as mandatory header keyword here for example (although it is briefly mentioned in the IRF axes section). Maybe it is better to mention these key word in the description for the IRF itself?
We need to document this and CREFN
is a strange choice for BinTableHDUs, since all metadata concerning columns are stored in keywords called TXXXXN
, (TTYPEN
, TUNITN
etc.)
CUNITN
as mentioned in the docs currently is not needed, since this is already covered by TUNITN
.
We need to update this for the next version to something we agree on so it can be implemented in the science tools.
So I would propose for bin tables to use TREFN
instead of CREFN
( C
is for image hdus).
Or more descriptive TAORD<N>
for Axis order?
Hi, I checked how it is nowadays in the MAGIC DL3 files and CREF is filled in
Friends, I fear we have to discuss IRF axis order again and work on it some more.
This was discussed in #28 and I thought we had fixed / concluded the discussion, basically agreeing to put a "recommended axis order" in the spec (see e.g. current EDISP spec), but also agreeing that we should use the
CREF
key from the OGIP multi-dimensional dataset FITS recommendation (see here and mention of that in our spec here). The advantage of usingCREF
is that it's more flexible, someone could change it e.g. for performance reasons, and when adding new IRFs with new axes there's a general scheme to declare in the file, not just in the spec, how to process the IRF.Currently I see this status:
CREF
header keys. @woodmd - do you rely on it in the Fermi ST, i.e. is it required in the Fermi-LAT IRFs?CREF
(cc @jknodlseder @gernotmaier)CREF
(cc @lmohrmann )CREF
(cc @TarekHC )CREF
(cc @thomasarmstrong)What I did was to check AEFF files. They all have this to specify the IRF array shape:
but they are lacking this to specify the IRF axis order (except for Fermi-LAT and older OGIP IRFs):
That example was what should be there for 10 energy bins and 5 theta bins, and following the recommended axis order of
energy, offset
forAEFF
as given here.Do you agree
CREF
is useful? If yes, could you please update your IRF FITS writers and readers?I'm not sure what to do about the spec. It depends on what people say here. My suggestion would be to add a note that
CREF
is required from now on for writers, but we keep the recommended axis order in the spec and a suggestion that readers look for CREF first, and if it's missing fall back to the hard-coded recommended order for the current IRFs we have. This means everything keeps working, but we get (in my opinion) better files from now on.