Re: transformation of co-ordinates

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1 total messages Started by Arthur J Lembo Tue, 09 Nov 1993 17:23

#61

Author: Arthur J Lembo
Date: Tue, 09 Nov 1993 17:23

23 lines
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In article <9311090618.AA27135@relay1.UU.NET> Prabhat K Vaish
<nicnet!GISD!pkv@UUNET.UU.NET> writes:
>In order to register maps or coverages, it is required to transform
co-ordinates
>of all coverages into a common coordinte system. Now to transform coordinates
>in 2-dim, one requires only 3 points to define affine transformation.
>
>My query to the netland is

>
>1. Why do we need 4 or more points to correctly define the transformation.
The three points allow for the creation of six equations (x and y) and
these equations exactly solve for the 6 unknown parameters (1 rotations
2 translations, 2 scale changes, and a non-perpendicularity of the axes.)
The four, or more points give a least squares solution, as you have more
equations than unknowns. >
>


>
>
>pkv
>..!uunet!nicnet!GISD!pkv

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