Geografic-Information-System/general/g.transform/g.transform.html

<H2>DESCRIPTION</H2>

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


<H2>NOTES</H2>

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

<p>
The transformations are:
<p>
order=1:
<div class="code"><pre>
    e = [E0 E1][1].[1]
        [E2  0][e] [n]
   
    n = [N0 N1][1].[1]
        [N2  0][e] [n]
</pre></div>

order=2:
<div class="code"><pre>
    e = [E0 E1 E3][1 ] [1 ]
        [E2 E4  0][e ].[n ]
        [E5  0  0][e&sup2;] [n&sup2;]
   
    n = [N0 N1 N3][1 ] [1 ]
        [N2 N4  0][e ].[n ]
        [N5  0  0][e&sup2;] [n&sup2;]
</pre></div>

order=3:
<div class="code"><pre>
    e = [E0 E1 E3 E6][1 ] [1 ]
        [E2 E4 E7  0][e ].[n ]
        [E5 E8  0  0][e&sup2;] [n&sup2;]
        [E9  0  0  0][e&sup3;] [n&sup3;]
   
    n = [N0 N1 N3 N6][1 ] [1 ]
        [N2 N4 N7  0][e ].[n ]
        [N5 N8  0  0][e&sup2;] [n&sup2;]
        [N9  0  0  0][e&sup3;] [n&sup3;]
</pre></div>

["." = dot-product, (AE).N = N'EA.]
<p>
In other words, order=1 and order=2 are equivalent to order=3 with
the higher coefficients equal to zero.


<H2>SEE ALSO</H2>

<EM><A HREF="i.rectify.html">i.rectify</A></EM>


<H2>AUTHORS</H2>

Brian J. Buckley<br>
Glynn Clements<br>
Hamish Bowman

<p>
<i>Last changed: $Date$</i></p>