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open-gamma-ray-astro / gamma-astro-data-formats

Data formats for gamma-ray astronomy
https://gamma-astro-data-formats.readthedocs.io
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Observatory location keys for headers #108

Closed cdeil closed 6 years ago

cdeil commented 6 years ago

@jknodlseder @kosack all - How should we store observatory location in the FITS header?

What we mention currently is GEOLON, GEOLAT and GEOALT in the POINTING spec: https://github.com/open-gamma-ray-astro/gamma-astro-data-formats/blame/48988405270a433a89ec6de19c1f4bc0db4bc417/source/events/pointing.rst#L46

For the EVENTS, in HESS and for the CTA 1DC files we use GEOLON, GEOLAT and ALTITUDE, e.g. for HESS:

GEOLAT  = -23.2717777777778 / latitude of observatory (deg)
GEOLON  = 16.5002222222222 / longitude of observatory (deg)
ALTITUDE=            1835. / altitude of observatory (m)

Our spec says nothing what to put for EVENTS, but I think we should be consistent with POINTING.

The FITS standard only mentions OBSGEO-X, OBSGEO-Y, OBSGEO-Z, not the keys we use.

Looking around, it seems different telescopes / missions use different keys.

Thoughts?

cdeil commented 6 years ago

I've attached a commit here to document how observatory location is currently stored in EVENTS FITS headers.

@lmohrmann @jknodlseder or anyone interested - Please comment.

lmohrmann commented 6 years ago

:+1:

cdeil commented 6 years ago

Merging now. As always, this spec is work in progress; comments always welcome.