| 摘要 |
A polygon of an electronic map is prepared for dividing into quarter sections and tests are applied to determine if the polygon is too irregular for quarter sectioning. To prepare for quarter sectioning, a representative rectangle is defined having corners matching corners of the polygon. Tests to determine if the polygon should be quartered begin with a first test to weed polygons too triangular in shape. In the first test, ratios of the shortest to the longest length of opposite sides of the representative rectangle are taken. If either ratio is less than a predetermined number, the polygon is rejected from quarter sectioning. In a second test an angle difference is determined by measuring the angle each side of the representative quadrilateral makes with respect to the x-axis. If the difference in angles between two opposite sides is greater than a predetermined value, the polygon is rejected from quartering. A third test determines how close the representative rectangle comes to actually representing the polygon's shape by determining the distance between points on the polygon and the representative rectangle, and rejecting the polygon from quartering if any distance is greater than a predetermined amount. A fourth test determines how close the side of the representative rectangle follows the true lines of the polygon by determining a ratio of the total length of lines of the polygon connecting two corners to the length of a side of the representative rectangle connecting the corners, and if the ratio is greater than a predetermined number, rejecting the polygon from quartering.
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