Hi Richard,
I've always said I wish most scientist would not write code... FITS is exhibit A. I doubt Juan would disagree.
Wholeheartedly agreeing!
Is there anything I can do in TheSkyX to make the warning go away? We've followed the same spec for 16 years. I can provide sample .fits files if needed as well.
If you are writing these SITELONG and SITELAT keywords following the format described by SBIG in their FITS extension document, then there will be no problems.
To be 100% precise, what we expect is a sequence of one, two or three floating point numbers separated by single spaces or colon (':') characters. These numbers represent degrees, minutes and seconds of arc, with minutes and seconds in the [0,60) range. Longitude should be either in the [-180,+180] range or in the [0,360) range, latitude in [-90,+90]. Longitude is positive east of the reference meridian, latitude is positive north of the equator. So for example, the following keyword values will be correctly parsed without errors:
'120 34 75.493'
'2.123456'
'-23 45.67'
'+44:25:12'
Anyway, we prefer the LONG-OBS, LAT-OBS and ALT-OBS nonstandard keywords for geodetic longitude, latitude and height in meters, mainly because they are 'coherent' with the standard DATE-OBS keyword name. The expected formats are the same.
Finally, should we use the OBSGEO-B, OBSGEO-L and OBSGEO-H keywords defined in the FITS standard 4.0 document instead (or, better, along with) these ones?
(Not to derail this, but I also think .xisf might be a better solution for video than .SER files. Anyone else think so?)
Very interesting idea. An extension to the XISF format for serialization of video sequences should be relatively easy to formalize. By compressing the entire video sequence using byte shuffling and a fast nondestructive codec, such as LZ4HC (which is as fast as pure LZ4 for decompression and almost as efficient as zlib for compression), we could achieve high compression ratios and real-time decompression with zero degradation. This is because the difference between two consecutive video frames is typically very small, so there should a lot of redundancy in the data stream. We have all the required resources to do this already defined and implemented in XISF.
When I can catch my breath, I'm going to start adding support for .xisf directly to TheSkyX. Make no mistake though, FITS is not going away, there's too many in the scientific community and our institutional customers that rely on it.
That would be very nice of you. I say this not because you are supporting a format that we have created, but because that would be a strong step forward to achieve the levels of modernization, standardization, efficiency and interoperability that we urgently need in the astronomy community. I started the XISF project exactly with this purpose, but unfortunately—although not surprisingly—it has been received more as a threat than as an attempt to improve the way we work with our data. One would expect more capacity of innovation and mental plasticity, and less resistance to change, from people doing science.
