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TriangularInterpolation and SetPrecision bug


I use TriangularInterpolation from the package ExtendGraphics to create
an interpolating function [salt] over a set of 3d data. When I apply the
function to a matrix of 3d coordinates[data]  inside the area
interpolated some values are read
as outside the domain of the interpolating function (lets say,
salt[data[[i,j,1]],data[[i,j,2]]]
for some [i,j] give {Indeterminate,Indeterminate}). Nevertheless the
interpolating function applied to the explicit numeric  values itself
of  [data[[i,j,1]],data[[i,j,2]]], lets say salt[12.8,6] gives the right
outcome (Lets say 1.96).
I have tried to change the format of  the argument of the interpolating
function (lets say [data[[i,j,1]],data[[i,j,2]]] ) to allow the function
to read them as "different" numbers using:
1) [IntegerPart [data[[i,j,1]]]+
FractionalPart[data[[i,j,1]]],IntegerPart [data[[i,j,2]]]+
FractionalPart[data[[i,j,2]]]]
or
2) [N[data[[i,j,1]]],N[data[[i,j,2]]]]
but this does not work as the problem is still presented.
3) Things get worse using SetPrecision as
[SetPrecision[data[[i,j,1]],3],SetPrecision[data[[i,j,2]],3]] because
the calculations are not only long but the outcomes are completely
crazy.
If someone has tackled this kind of handicap please let me know.



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