[Proj] proj deployment question

[Frank Warmerdam]

jjholt at hiwaay.net wrote:
> I have created a VC++ COM component that our application uses for projection
> services. It links with proj as a static Win32 library to do the actual projection.
> 
> It works great, but I'm wondering about deployment issues. Normally I thought
> the proj library requires some files - eg "nad" directory and maybe others.
> However my component seems to work even on systems without any other proj files
> on it.
> 
> We only do relatively simple stuff - geographics to/from UTM, geographic to from
> Mercator, and UTM zone to zone. Is that why? Maybe "nad" is only needed for
> "datum shifts"? I don't know what a "datum" is, let alone how to shift one :-)
> 
> I suppose another way to put it is: what capabilities won't work without
> external proj files?

Jeff,

Without the contents of the nad directory you won't be able to use the
init files (eg. +init=epsg:4326) or do grid shift based datum shifts
(ie. NAD27 -> NAD83).  Also the default values found in proj_def.dat won't
be in play - so you may need to be explicit about things like ellipsoid
for instance.

If you are careful to fully define your coordinate systems, the only real
capability you should be missing is the grid shift datum shifting.  Note
that +towgs84 datum shifting will still work.

PS. There is a modest COM component now found in proj/com.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | President OSGeo, http://osgeo.org