[OSRS-PROJ] Re: Proj.4 DLL ?

[Bart Adriaanse]

Hi Frank,

I did some testing using the proj.exe command line mode.

The Dutch projection works absolutely perfect with the parameters you
suggested, only the datum shift parameters seem to be ignored on the
command line.

The fact that it does the projection so nicely made us decide to drop
other alternatives like GCTP and Geotrans and use PROJ.4 for our
projects from now on. 
I suppose we will get the datum shift to work somehow, maybe with a
little advice from you. 

Whatever improvements we might make on the code itself we will surely
feed back to you, but the idea is to use the DLL "as is" without any
modifications.

Thanks a lot for your support sofar !

Bart Adriaanse
Demis bv
The Netherlands
www.demis.nl




> -----Original Message-----
> From: Frank Warmerdam [mailto:warmerdam at pobox.com]
> Sent: Tuesday, January 23, 2001 3:58 PM
> To: Bart Adriaanse
> Cc: osrs-proj at remotesensing.org
> Subject: [OSRS-PROJ] Re: Proj.4 DLL ?
> 
> 
> Bart Adriaanse wrote:
> > 
> > Hi Frank,
> > 
> > I have been spending some time reading, including the mailing list
> > archive on Proj.4, i hope you will alow me to ask you two 
> big questions
> > i have.
> > 
> > I noticed you mentioning in a posting that the datum 
> transformations are
> > not included in the DLL and you sort of offered to help if that was
> > required.
> > If i look at some of the sources i get the impression it 
> still is that
> > way and i would like to estimate how hard it would be to 
> incorporate the
> > datum conversion, in the same DLL or in a seperate one. 
> Would you think
> > this to be easy to to ?
> 
> Bart, 
> 
> The datum shifting works fine in unix .so files, the only problems on
> windows is that I haven't added all the entry points to the 
> proj.def file.
> It shouldn't be hard.  I would encourage you to do it, and 
> send me back the
> updated proj.def file.  If you have problems with the datum 
> shifting support
> (which is pretty new) I am glad to help. 
> 
> Mainly I think you need to add the pj_transform entry point 
> to proj.def, but
> there are a bunch of other function called less often by the 
> application that
> could also be added, such as pj_datum_transform, 
> pj_geocentric_to_geodetic, 
> pj_geodetic_to_geocentric, and pj_compare_datums. 
> 
> > Second question, have you ever heard of the dutch RD national grid
> > projection, specifically if this can be handled within reasonable
> > accuracy with proj.4 ?
> > I have some simple fifth degree polynomal formula's from the dutch
> > topographic dept. so we could even dream of adding this to Proj.4 ?
> > (what i am missing is the Bessel1841->WGS84 datum shift to make it
> > usable)
> 
> My lookup in the EPSG database says that the RD projection is based on
> Oblique Stereographic which I currently map to the "stere" 
> projection in
> PROJ.4.  I have no personal experience with how accurate this 
> is though. 
> 
> The EPSG database include a 7 parameter transformation to WGS84 from
> Amersfoort.  You should definately check the results of this, since I
> have only done decent testing on the 3 parameter datum 
> transformations,
> not the seven.  My unvalidated hand translation of EPSG CS 29882
> (RD / Netherlands New) would be:
> 
> +proj=stere +lat_0=52.1561605555555 +lon_0=5.38763888888888 
> +k=0.9999079
>             +x_0=155000 +y_0=463000 
>             
> +towgs84=593.16,26.15,478.54,-6.3239,-0.5008,-5.5487,4.0775
>             +ellps=bessel
> 
> Let me know if this produces reasonable results. 
> 
> 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/~warmerda
> and watch the world go round - Rush    | Geospatial 
> Programmer for Rent
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