[Proj] NTv2 info

Gerald I. Evenden geraldi.evenden at gmail.com
Sun Jun 7 13:57:09 EST 2009

> In the case of the NGS NADCON files, an Intel machine can process them
> without byte flipping.

Did I write that?  Hmmm.  Sorry about that.

As NTv2 has been solved I reexamined the NADCON stuff which dates back to 
the '80s with little updating on my part.

Given the current distribution of NGS NADCON, they deserve as many lashes with 
wet noodles as the Canadians.  C'mon, a file each for the 
east-west/north-south correction.  Only thing giving NGS points over the 
Canadians was column order and negative longitude.  No ethnogeodetic problems 

I do not know where the NGS detailed description of the file format is but 
they do distribute source code for routines reading the files.  With effort 
the format can be resolved from the FORTRAN code.  It reminds one of the 
principle deficiency of the FORTRAN language.  It was the reason I often had 
to resort to assembly in order to translate files into FORTRAN processable 

It might even be an idea to translate the NADCON files into NTv2 but suspect 
that overlapping areas with enhanced precision might not fit the scenario of 
NTv2 sub-files.

Maybe someone has already done it.

At least, it seems to be a good idea to build a directory file for the NADCON 
distribution that summarized the regions and thus enhances lookup.

The whole religious complexion of the modern world is due
to the absence from Jerusalem of a lunatic asylum.
-- Havelock Ellis (1859-1939) British psychologist

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