After-Class review of GIS: Spatial data Processing-1.1 coordinate transformation

coordinate transformation is to realize the transformation of the coordinate system of digitized data and the correction of drawing distortion error. It is divided into affine transformation, similarity transformation and two times transformation.

1) affine transformation (affinetransform)

That is, the coordinate transformation:

Set: X, y for the digitizer coordinates, X, y for the theoretical coordinates, M1, M2 for the map landscape and longitudinal actual scale, the two coordinate system angle is а, the digitizer Origin o ' relative to the theoretical coordinate system origin translation A0, B0.
According to the principle of graph transformation, the formula of coordinate transformation is as follows
x = a0 + (M1 * cosа) * x + (m2 * sinа) * y
y = B0-(M1 * sinа) * x + (m2 * cosа) * y
Among them, set
A1 = M1 * Cosа
B1 =-M1 * sinа
A2 = m2 * sinа
b2 = m2 * cosа
The above formula can be:
X = a0 + a1 * x + a2 * y
y = B0 + b1 * x + b2 * y

2) similar transformations• From one graphic to another, keep the shape constant during the change (size direction and position variable), such that the graph changes a similar transformation called a graph. • Any similarity transformation can be decomposed into a composite of the retraction, translation, rotation, and rollover transformations. • Similarity transformation is a special case of affine transformation, which is the result of removing the factor of dislocation transformation in affine transformation. 3) Two-time transformationCopy to here, prepare for lesson after review ~    

After-Class review of GIS: Spatial data Processing-1.1 coordinate transformation