## NAME

g.transform

## DESCRIPTION

g.transform is an utility to compute transformation based upon GCPs and output error measurements.

## NOTES

For coordinates given with the coords file option or fed from `stdin`, the input format is "x y" with one coordinate pair per line.

The transformations are:

order=1:

        e = [E0 E1][1].[1]
            [E2  0][e] [n]

        n = [N0 N1][1].[1]
            [N2  0][e] [n]

order=2:

        e = [E0 E1 E3][1 ] [1 ]
            [E2 E4  0][e ].[n ]
            [E5  0  0][e²] [n²]

        n = [N0 N1 N3][1 ] [1 ]
            [N2 N4  0][e ].[n ]
            [N5  0  0][e²] [n²]

order=3:

        e = [E0 E1 E3 E6][1 ] [1 ]
            [E2 E4 E7  0][e ].[n ]
            [E5 E8  0  0][e²] [n²]
            [E9  0  0  0][e³] [n³]

        n = [N0 N1 N3 N6][1 ] [1 ]
            [N2 N4 N7  0][e ].[n ]
            [N5 N8  0  0][e²] [n²]
            [N9  0  0  0][e³] [n³]

["." = dot-product, (AE).N = N'EA.]

In other words, order=1 and order=2 are equivalent to order=3 with the higher coefficients equal to zero.

## SEE ALSO

i.rectify

## AUTHORS

Brian J. Buckley
Glynn Clements
Hamish Bowman

Last changed: $Date: 2011-11-08 12:29:50 +0100 (Tue, 08 Nov 2011) $

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