[fitsbits] reopening of Public Comment Period on the Green Bank convention

[Arnold Rots]

Let me make sure I get this right:
I suspect you mean that the second axis is one pixel long.
If it were zero pixels long, there would be no pixels in the image at all.
I note that this mechanism (single-pixel axes) has been used extensively
in radio astronomy to specify the polarization and frequency of 2-D images.

Cheers,

  - Arnold

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Arnold H. Rots                                          Chandra X-ray
Science Center
Smithsonian Astrophysical Observatory                   tel:  +1 617 496
7701
60 Garden Street, MS 67                                      fax:  +1 617
495 7356
Cambridge, MA 02138
arots at cfa.harvard.edu
USA
http://hea-www.harvard.edu/~arots/
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On Thu, Jun 2, 2016 at 1:04 AM, William Pence <William.Pence at nasa.gov>
wrote:

> On 6/1/2016 11:14 AM, Demitri Muna wrote:
>
> There is a significant difference between documenting use of the FITS
> format and incorporating it into the standard. As an example, I recently
> came across UV data, which immediately crashed my FITS viewer, and then
> this in the AIPS File Format Memo:
>
> In the UV-tables form, the visibility data are written as a FITS binary
> table, normally placed after the other table extensions. The primary HDU
> has an AIPS conventional form meant primarily to be so odd as to act as a
> reliable identifier. The primary HDU asserts that the primary data has two
> axes, the first of which has 777777701 values while the second has zero
> values. This is sufficient to tell all FITS readers that the primary data
> set is not a random groups data set and otherwise contains no data.
>
> This may be convention, but it's *lying*. I'm sure that there are untold
> numbers of FITS files of UV data that use this convention. Should it be
> part of the standard? Absolutely not.
>
> It is legal for a FITS image to have one or more zero length axes as well
> as other non-zero length axes, so these UV visibility data do conform to
> the requirements of the FITS standard and are not lying.  One could say
> that these 2D images really are 777777701 pixels wide, but because they are
> 0 pixel high they are hard to see.  :-)
>
> -Bill
>
>
>
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