[Proj] Environment variable et proj.4 vb wrapper

Eric Miller EMiller at dfg.ca.gov
Tue Aug 8 11:16:48 EDT 2006

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
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
state coordinates. This is my first attempt to use proj4 and I don't
what I do wrong.
Here is the definition I use :
WGS 84 (epsg : 4326) : +proj=longlat +ellps=WGS84 +datum=WGS84
no_defs <>
Lambert 72 Belge (epsg : 31370) : +proj=lcc +lat_1=51.16666723333333
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. 
> seem to recall it doesn't work due to calling convention issues.
> If you can figure out how to change the PROJ_LIB environment
> 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
> Lambert 72 (Belgium) and from Lambert 72 to WGS 84. I want to
> these
> functions by the proj.4 vb wrapper so I can use this software in
> 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
> 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.
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