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               Bilinear Interpolation
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Programmer:

Andreas R. Stokholm, 
Technical University of Denmark, 
DTU Space, Division of Geodynamics

Contact: stokholm@space.dtu.dk
Do not hesitate to contact if bugs or problems arise.

Supervisor:
René Forsberg
Technical University of Denmark, 
DTU Space, Division of Geodynamics
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Updated last:
.27-05-2019
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Program Function:

This program provides bilinear interpolation 
utilities by enabling a grid and data set upload. 
Program output is a txt file with the interpolated 
values in the same order as uploaded. If data and 
grid does not overlap the output file will be
empty. 'Choose Grid' button referes to desired GRI file
to use in the program. 'Choose Data' is similar but for 
data points.

Grid data should be in the .GRI gravsoft format
with header containing LatLon min & max and grid 
spacing.

Additional features include 'Transform', which
subtractes or adds interpolated values from supplied
values. Transformation index referes to the column in the
data set, which contains the values to subtracted or added to.
It is also possible to use single point interpolation by 
typing in a LatLon coordinate. 
Once a grid has been loaded, it does not need to
reload it, unless a different file has been
selected or program is closed. Double values should be
Separated by a dot (.).
The program cannot output data to a file that is open,
therefore ensure that files are closed.

To change background image edit the file 
'background.jpg', remove it and add a new one.
File must be jpg and called 'background'.
Icon can be changed too, by editing 'icon.gif'.
File must be gif and called 'icon'. Even though
file is a gif, it can be a still image i.e. a gif
with one frame.