[OSRS-PROJ] Using NAD27/NAD83 datum in the DLL

[Bart Adriaanse]

Thanks again for your guidance Frank,

Good to hear from you that the pj_transform function should take care of all
this, i guess my only problem is to make it find the file in the right
place, i might just hack the code a bit like you suggest, maybe a generic
way of specifying a path for these files other then setting up an
environment variable would be a usefull option for a future release ?

Any news on version 4.4.4 yet ?

Best Regards,

Bart Adriaanse
Demis bv


----- Original Message -----
From: "Frank Warmerdam" <warmerdam at pobox.com>
To: <osrs-proj at remotesensing.org>
Sent: Monday, April 16, 2001 3:22 PM
Subject: Re: [OSRS-PROJ] Using NAD27/NAD83 datum in the DLL


> Bart Adriaanse wrote:
> >
> > With some help earlier from Frank i compiled the DLL for windows and i
am
> > using the pj_transform to do the coordinate transformations, it works
very
> > well sofar !
> >
> > Now how would i go about using NAD in this scenario, i suppose i will
need
> > to call nad_init to read the NAD data file but can i have both of them
> > loaded at the same ? and would this be sufficient to be able to convert
like
> > wgs84 to nad83 just by specifying the datum name in pj_init ?
> >
> > Any hints would be greatly appreciated,
> >
> > Sorry if this is documented someplace, i tried, but could not find it,
>
> Bart,
>
> Since you are using pj_transform() it should be easier than that.  You
> should just need to include the datum definition in your coordinate system
> definition.  For instance "+proj=utm +zone=11 +datum=NAD27".  This will
cause
> pj_transform() to load the "nad27" datum shift file for shifts from nad27
> to nad83 or vice versa.
>
> The +datum switch just expands into a definition like
> "+nadgrids=conus +ellps=clrk66" so if you want to use other datum shift
files,
> such as the various state level files, alaska, Puerto Rico and so forth,
you
> will need to use more specific +nadgrids directives.
>
> eg.
>
> +proj=utm +zone=11 +nadgrids=hawaii +ellps=clrk66
>
> The other issue is ensuring the files are found.  A default unix
installation
> puts the various support files in /usr/local/share/proj but on Windows or
> in custom situations you may need to hack pj_open_lib.c to look in your
> desired directory.  This can be done by modification of the code, or by
> setting the PROJ_LIB environment variable.
>
> I hope this helps.
>
> 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
> and watch the world go round - Rush    | Geospatial Programmer for Rent
> ----------------------------------------
> PROJ.4 Discussion List
> See http://www.remotesensing.org/proj for subscription, unsubscription
> and other information.
>

----------------------------------------
PROJ.4 Discussion List
See http://www.remotesensing.org/proj for subscription, unsubscription
and other information.