[Proj] How to convert a sphere to ellipsoid with correct datum?

support.mn at elisanet.fi support.mn at elisanet.fi
Mon Sep 6 08:04:53 EST 2010


The datum shift (towgs84...) is exactly what you need to fix most of the
common errors found in most local mapping datums. It can fix x-y-z-shif,
x-y-z-rotation and scale (7 parameter version). If you need more
adjustment, you have to add some polynomial fitting function
somewhere between the input and output.

There are methods to find those parameters when given some
data to be fixed. 60 m should not be any problem.

If that was not the question I answered it anyway.



Jan Hartmann [j.l.h.hartmann at uva.nl] kirjoitti: 
> Again thanks for your help: I am now confident that converting latlon 
> values on different ellipsoids give correct results when using 
> +towgs84=0,0,0 to both parameter lists. I still have to hunt for the 
> last 60 meters of accuracy, though. The devil is, as always, in the 
> latest en finest detail.
> Jan

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