[FWTools] datum shifting in FWTools

[Roger André]

Sorry about the separate post about this, but I suspect the answer to this
question might actually be "no", at least in the Linux version.  The
share/proj directory in FWTools is lacking a "null" executable.  Since the
"proj-datumgrid-1.4.tar.gz" download contains a ".lla" file for all of the
other grids present (conus, hawaii, stgeorge, etc), as well as a "null.lla"
file, I assume that the lack of a "null" executable implies that proj was
built without this grid-shift file.

If someone else more knowledgeable about proj could confirm this for me, I
would appreciate it.

Roger
--

On Mon, Oct 20, 2008 at 7:11 PM, Roger André <randre at gmail.com> wrote:

> Thanks Frank,
>
> I'm trying to narrow down the problems I'm having with a projection, and
> that "+nadgrids=@null" parameter is new to me.  Someone told me that I might
> need to install a separate set of files to enable it.  Just wanted to check
> and make sure.
> --
>
>
> On Mon, Oct 20, 2008 at 8:01 PM, Frank Warmerdam <warmerdam at pobox.com>wrote:
>
>> Roger André wrote:
>>
>>> Is it possible in FWTools to use a projection which specifies the
>>> following, "+nadgrids=@null"?
>>>
>>
>> Roger,
>>
>> Yes, it should work with the FWTools PROJ.4 tools (and related stuff
>> like MapServer).  If you want to use it with GDAL and OGR it is a bit
>> more involved.  I think you need to add +wktext in the PROJ.4 definition
>> so that GDAL will "capture" the literal PROJ.4 definition in the internal
>> WKT representation so the nadgrids part won't get lost.
>>
>> Best regards,
>> --
>>
>> ---------------------------------------+--------------------------------------
>> I set the clouds in motion - turn up   | Frank Warmerdam,
>> warmerdam at pobox.com
>> light and sound - activate the windows | http://pobox.com/~warmerdam<http://pobox.com/%7Ewarmerdam>
>> and watch the world go round - Rush    | Geospatial Programmer for Rent
>>
>>
>
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