This file contains code to implement grid based transformation of 
latitude/longitude coordinates using an NTv2 ascii formatted file.
It is intended for the conversion of latitudes and longitudes between
the New Zealand geodetic datums NZGD1949 and NZGD2000.  

This is a minimal implementation of a grid transformation with some
significant limitations including:
  1) It cannot work with the binary NTv2 format 
  2) It does not support subgrids - it only works with a single grid
  3) It always loads the entire grid into memory - there is no
     load on demand or caching
  4) It only calculates the adjustment to coordinates, not the
     error of the adjustment.

This software may be freely used and modified.  It is provided as is, 
where is, with no guarantees as to its correct functioning.  Land
Information New Zealand accepts no liability for any consequences 
of the use of this software.

The makefile provided can be used to compile the program testlinzgrid which 
implements the linzgrid functions.

The NTv2 file used for the NZGD1949 to NZGD2000 transformation is
nzgd2kgrid9911.asc, which may be downloaded from the LINZ website.

This module can also compile the NTv2 grid into a source code file
linzgridnzgd2k.c.

The makefile can also generate test output files (make test) which can
be compared with check.out, which has the correct values.  Expect rounding 
errors in the last significant digit.

The makefile is designed for use in a linux system.  It is very simply structured
and may be readily ported to other systems.

This is version 1.3 of the linzgrid code.  It differs from the previous version in
that the grid loading function is in a separate module.  See comments in linzgrid.c
for a description of the linzgrid API. 

Contents of this zip file should be

linzgrid.c         Main grid functions, calculations and destructor
linzgrid.h
linzgridload.c     Function for loading an ASCII NTv2 file
linzgridload.h
testlinzgrid.c     Main program for testing the NTv2 loader
writegridsource.c  Main program to create a source file from the NTv2 grid
makefile           Make file to build all components
test.in            Test input file
check.out          Check output file
README             This file


