Coordinate system Tiepoints editor |
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Transformation |
Edit menu |
When editing a coordsys tiepoints, select the transformation method with which the relation between the artificial XY-coordinates and the correct XY-coordinates of your tiepoints should be calculated.
In the formulae below:
Dialog box options:
Select one of the transformation methods:
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Plane, minimum of 2 tiepoints required; Xout = aX + bY + c1 Yout = bX - aY + c2 |
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Plane; recommended; minimum of 3 tiepoints required; Xout = a11X + a12Y + b1 Yout = a12X + a22Y + b2 |
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Second degree linear surface; minimum of 4 tiepoints required; Xout = a1 + b1X + c1Y + d1XY Yout = a2 + b2X + c2Y + d2XY |
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Full second degree polynomial surface; minimum of 6 tiepoints required; Xout = a1 + b1X + c1Y + d1XY + e1X2 + f1Y2 Yout = a2 + b2X + c2Y + d2XY + e2X2 + f2Y2 |
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Third degree polynomial surface; minimum of 10 tiepoints required; Xout = a1 + b1X + c1Y + d1XY + e1X2 + f1Y2 + g1 X3 + h1 X2Y + i1XY2 + j1 Y3 Yout = a2 + b2X + c2Y + d2XY + e2X2 + f2Y2 + g2 X3 + h2 X2Y + i2XY2 + j2 Y3 |
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Recommended for oblique vector maps; minimum of 4 tiepoints required; Xout = (aX + bY + c) / (gX + hY +1) Yout = (dX + eY + f) / (gX + hY + 1) |
The transformation method and calculated sigma are visible at the top of the tiepoints table.
Tip:
For each transformation method, a certain number of tiepoints is mathematically required. It is advised to always add more tiepoints than the absolute minimum number required.
See also: