[GRASSLIST:2017] Re: Representation of "no data": we need your opinion

[Rod Paterson]

>Subject: [GRASSLIST:2015] Representation of "no data": we need your opinion

>What we would like you to do is provide us with your opinion on whether
>we should keep the feature of 0 being interpreted as "no data". To make
>things a little easier, we would like you to REPLY TO THIS POST stating
>which of the following options you wish to support:
>
>    a) Full legacy interoperability: keep the feature of 0 being
>       optionally interpreted as "no data"
>
>    b) Transition from GRASS 5.0 onwards: keep the feature of 0 being
>       optionally interpreted as "no data" in GRASS 5.0 only,
>       eliminating it in subsequent releases
>
>    c) Transition now: eliminate the feature from GRASS 5.0, but
>       provide a script to convert GRASS 4.x files to GRASS 5.0 format
>       for those who wish 0 to be NULL
>
>    d) Any of the above, ie it doesn't matter to me how this problem is
>       solved
>
>Thank you for your time in this matter.
>
>--
>Sincerely,
>
>Jazzman (a.k.a. Justin Hickey)  e-mail: jhickey at hpcc.nectec.or.th
>High Performance Computing Center
>National Electronics and Computer Technology Center (NECTEC)
>Bangkok, Thailand


Preferred option is none of the above;

Why not allow the NULL value to be defined in the raster header file;
This would be more flexible and only involves editing of the header;
Using raster data from other software which uses this approach (ie ERMapper)
would be easier removing the need for any conversion.

Is there a performance penalty in doing this?

Therefore my prefered option would be a modified a)

ie. a) Full legacy interoperability: but allow any selected value to be
         optionally interpreted as "no data".

   regards
   Rod Paterson
   Consulting Geologist
   10 Howitt Street
   Glen Iris Vic., 3146

   Phone: 61-3-98892793
   Fax:   61-3-86100373
   Email: rpaterso at bigpond.net.au