[OSRS-PROJ] Re: Quick 'how-to' to on PROJ.4

[Frank Warmerdam]

Precedence: bulk
Reply-To: osrs-proj at remotesensing.org

"Petri J. Riipinen" wrote:
> 
> Precedence: bulk
> Reply-To: osrs-proj at remotesensing.org
> 
> Hello,
> 
> Hmm... I might be out of my league now, but do you think that the
> inaccuracy might come from the datum shift? I just learned that there are
> 3- and 7-parameter shifts. Should a 7-parameter shift be used for a better
> accuracy?
> 
> At least in this page:
> http://www.kms.dk/research/geodesy/reference/cotrans1_en.html there seems
> to be 7 parameters for WGS84 - ED50 - transformation. Would this help?
> 
> On this page: http://www.nls.fi/kartta/julkaisu/kkj.html there is some
> (IMO) simple transformation formula. Do you think that this formula would
> give me good enough results, if I can't get PROJ.4 to be accurate enough?
> At the end of the page there is some example that might be a good reference
> point when trying the transformations with cs2cs.

Petri, 

The difference could be datum shift related, but it seems pretty significant
for being the datum.  You could of course build this transformation directly
into your package by hand if you will only ever be interested in KKJ/WGS84
conversion.  

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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