[Proj] NADCON spec

Eric Miller EMiller at dfg.ca.gov
Wed Sep 9 10:12:54 EST 2009

As far as I know the format is not documented.  NADCON uses two input files per datum adjustment (las / los).  Reportedly a utility program, NADGRD, will convert between an ASCII and the binary representation of the grid files.  So, that might be the route to take.  There's some documentation on the ASCII format on ESRI's website:


The FORTRAN source code could also be consulted.

Eric G. Miller
Staff Programmer
CA Dept. of Fish & Game

>>> On 9/9/2009 at 2:04 AM, Richard didier <didier.richard at ign.fr> wrote:
> Hi all,
> I need to produce NADCON grid from our NTV2 grid.
> I have searched the web for NADCON grids specs and only found that a NADCON 
> grid is a bundle including the data AND the software that reads them ... I, 
> also, found that there are two files needed (one for longitudes, another one 
> for latitudes) and that longitudes/latitudes must be round even values ... 
> But, I am not sure of all of that.
> On the other hand, PROJ.4 includes a reader for converting lla (ascii) to 
> binary ... and lla is mentioned in some web pages.
> So, is there "real" specifications for NADCON Grids ? and could someone 
> point 
> me to them ?
> Sincerely,

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