Coastline Matching Algorithm

The chain code generation works as follows.

Load prepocessed image

We start from preprocessed images.

Clean image

The preprocessed image is cleaned from errors, and noise caused by texts on the map. If we assume satellite images this step can be omitted. The process is made by hand, because the lack of time, though it could be done automatically.

Create point coordinates

First a thinning algorithm is used.

Then the starting point of the line has to be found. It can be done by simply examining the edges of the picture. Then the algorithm simply walks through the line and returns point coordinates. Not all points are reported, only points after a certain step, for example every 10th point.

(5,12), (12,34), (43,54), ...

Chain code generation

From the point list the chain code is generated directly. The format of the chain code is the following:

step_length, rotaion_angle, step_length, rotation_angle, ...

Then this path can be drawn with different scale and rotation

Implementation details

• The coordinate list generation was made by Joonas Lehtinen
• The chain code calculation was made by Jozsef Galajda

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