Re: [DebianGIS] Fw: Re: [Proj] NAD27 and WGS84 woes
On Wed, Nov 26, 2008 at 09:39:26AM -0500, Frank Warmerdam wrote:
> Francesco P. Lovergine wrote:
>> ntf_r93.gsb: data
>> ntv1_can.dat: data
>> nzgd2kgrid0005.gsb: data
>>
>> Three files are in binary format: the .gsb files are NTv2 binaries, the other
>> not (maybe NTv1?) I wonder if those files are managed correctly by proj
>> on all archs. I found a reference to NTv2 formats, but not for the second
>> file. Do you have more information about that?
>
> Frankie,
>
> the ntf_r93.gsb and nzgd2kgrid0005.gsb files are NTv2 format. The ntv1_can.dat
> file is NTv1 format. However, I don't see the distinction between these binary
> files and text data files like the US .lla files. A text file is not
> equivelent to readable, understandable and modifiable "source code".
>
As explained in the related bug report, I'm afraid that those blobs are not
endianess-safe. The NTv2 binary has an ASCII counterpart, so it is probably
better pre-convert them in ASCII format. Do you have a reference for the NTv1
format? Also, it's better avoiding binary blobs, which are always looked
with suspect by ftpmasters. A general problem anyway is about a missing
accompanying license for those files. People say they are public domain,
but there's no evidence about that. There are many places where they
are distributed, but this is does not imply they are public domain...
--
Francesco P. Lovergine
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