[Proj] Environment variable et proj.4 vb wrapper

[Gheysen Thibaut]

I have found the +towgs84 parameters on
http://www.geocities.com/mapref/mapref.html.
I have modified the lambert 72 definition to : "+proj=lcc +lat_1=
51.16666723333333 +lat_2=49.8333339 +lat_0=90 +lon_0=4.367486666666666 +x_0=
150000.013 +y_0=5400088.438 +ellps=intl +towgs84=-99.059,53.322,-112.485,-
0.419,0.830,-1.885,-1.0 +units=m +no_defs  no_defs <>"
The result are better but not good : I always have a difference of 80 meters


2006/8/8, Eric Miller <EMiller at dfg.ca.gov>:
>
> I think you need some datum transformation parameters on your Lambert
> projection.  See the +towgs84 parameter.  The EPSG database doesn't seem
> to have any datum transformation information for that coordinate system.
> So, that may be the best you can expect...
>
> >>> gheysen.t at gmail.com 8/8/2006 1:12:53 AM >>>
> Finally, I use the solution of changing the PROJ_LIB environment
> variable
> when my VB program start. I can now call the projection function
> (pjTransform) but the result are bad. I have a gap of about 100 meters
> between the real position and the projected coordinates.
> My aim is to project WGS 84 coordinates from garmin GPS to various
> european
> state coordinates. This is my first attempt to use proj4 and I don't
> know
> what I do wrong.
> Here is the definition I use :
> WGS 84 (epsg : 4326) : +proj=longlat +ellps=WGS84 +datum=WGS84
> +no_defs
> no_defs <>
> Lambert 72 Belge (epsg : 31370) : +proj=lcc +lat_1=51.16666723333333
> +lat_2=
> 49.8333339 +lat_0=90 +lon_0=4.367486666666666 +x_0=150000.013 +y_0=
> 5400088.438 +ellps=intl +units=m +no_defs  no_defs <>
>
> Someone can help me ?
>
> 2006/8/1, Eric Miller <EMiller at dfg.ca.gov>:
> >
> > That VB wrapper hasn't been updated to know about the
> > pj_set_searchpath() function.  I'm not sure if the pj_set_finder()
> > function will work.  You could try it.  See the AddressOf operator.
> I
> > seem to recall it doesn't work due to calling convention issues.
> >
> > If you can figure out how to change the PROJ_LIB environment
> variable
> > from within your VB program, that should work.  Just do it during
> > program startup before any proj.4 functions are called. Or, maybe,
> use a
> > batch file that launches your VB program and sets the PROJ_LIB
> > variable?
> >
> > >>> gheysen.t at gmail.com 8/1/2006 1:19:04 AM >>>
> > Hello,
> >
> > I have wrote a little program in vb to download and upload GPS data.
> > This
> > software use 2 specific functions to transform the data from WGS 84
> to
> > Lambert 72 (Belgium) and from Lambert 72 to WGS 84. I want to
> replace
> > these
> > functions by the proj.4 vb wrapper so I can use this software in
> other
> > contry than Belgium. I have test, without problem, this wrapper with
> > the
> > file "exemple.mdb".
> >
> > My problem is that I have Qgis installed and thus I have already a
> > "Proj_lib" environment variable. If user uninstall Qgis, the proj.4
> is
> > uninstall. How can I have two versions of Proj.4 install on the same
> > computer. I have read than I can use pj_set_finder() or
> > pj_set_searchpath()
> > to override this environment variable. This function is it available
> > through
> > the vb wrapper ? If yes, how can I use this in vb ?
> >
> > Thanks in advance.
> >
> > Gheysen Thibaut.
> > _______________________________________________
> > Proj mailing list
> > Proj at lists.maptools.org
> > http://lists.maptools.org/mailman/listinfo/proj
> >
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