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Thinning out XY corrdinates from MAP data when the data of PC MAP is exchange to PDA MAP Disclosure Number: IPCOM000045598D
Original Publication Date: 2005-Feb-07
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 88K

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A program is disclosed that the method is to simplify the polyline by eliminating the part of the points of the original polyline. This method, the judgment to eliminate the point by using the distance between the original point and the simplified line, has the advantage against the general two methods by using the angle and the length of the line segments. Generally, the angle method is useful for the smooth polyline, and the length method is useful for the detailed polyline and the scale-down polyline. In addition, this method provides the minimal logic to calculate fast for thinning out the points from the original line, because the judgment of the point elimination will be done in order from the one side of the polyline.

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Thinning out XY corrdinates from MAP data when the data of PC MAP is exchange to PDA MAP

Logic of the simplification of the polyline  (Thinning out the points of the polyline ) The following steps and the figure show the logic of this algorithm .

Step  1) The original polyline is A-B-C-D-E-F. At first, decide the limit distance(=L  on the figure), as a condition to eliminate the points from the original polyline . Step  2) Select the first three points, A, B and C, and judge the elimination of the  point B.  Measure the distance between the point B and the line A-C. When the distance is  shorter than L, the point B is eliminated. But, the point B will be still used for the  judgment of the next points.

Step 3) Select the point A, B, C and D, and judge the elimination of the point C . (Add the next point into the selection for the judgment, when the point is eliminated  on the previous step.)

 Measure the distance between the point B, C and the line A-D. When all of the  distances are shorter than L, the point C is eliminated, too. The point B and C will  be used for the judgment of the next points .

Step ...