[Proj] Old problems

Frank Warmerdam warmerdam at pobox.com
Tue Jan 3 23:09:19 EST 2006

On 1/3/06, Gerald I. Evenden <gerald.evenden at verizon.net> wrote:
> I do not see why the datum operations cannot be made a shell procedure process
> where the entries are nearly identical with libproj4.  Something like
> gx_init, gx_fwd, gx_inv, where gx_init feeds off the options related to
> datums and gives the list to pj_init to initialize the projection phase.


Indeed it is plausible to layer things this way, though it would be
change in API that would require changes in all applications
using PROJ.4 (at least that depend on datum, etc features)

> Remember, libproj4 pj_init ignores any options that it does not recognize.
> Also, does anyone use the default file or +init?

I would agree that the default file is a problem, and I wouldn't
be adverse to it disappearing all together.

The +init files though are widely used.  Especially the epsg file,
which is relatively new.

> I'd be glad to give up the pj_init, pj_fwd and pj_inv names and replace them
> with proj_init, proj_forward and proj_inverse in the libproj4 system.  Thus
> the libdatum could have the pj_* entries and minimize any hassles in changing
> application programs.  Any of the other less utilized entries would also
> prefix with proj_.  Note the structure pointer returned by the new pj_init
> would have a pointer to PJ returned by proj_init.

Well, I still think there are issues of conflicting definitions for the PJ
structure, layering the initialization logic and so forth.  It could all be done
but would require substantial work, and care to avoid unnecessary
disturbance to applications.

> Any comments?

My main comment is that I'm sure this will all happen.  It is
certainly my intention.  But it doesn't seem like there is any
compelling rush to make these changes.  For the time being
the two libs haven't diverged that much, and it is relatively easy
to migrate selected pj_*.c files into the remotesensing.org version
as needed.   If I was to take some time on PROJ issues, I
would likely dig into some of the Krovak, prime meridian and
related problems that folks have been trying to get me to move

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

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