In some cases it is desirable that the angles formed by the neighboring feature edges when adding line or area features could take only the values divisible by the specified value. For example, if one degree is selected as such a value, the values of all angles between edges will be evaluated by an integer number of degrees.
If a line or area feature type is selected on page “Input” of the window “Editor control”, the checkbox Fix edge angle enables the user to turn on such a mode when the angle between every edge being added and the previous added edge will be divisible by the value specified (in degrees) in the field Step to the right of the checkbox. The angle is measured in counter-clockwise direction from the previous edge and can be changed from 0° to +360°. As a rule, it is convenient for the user to select such a value for fixation step which entirely divides the right angle (for example, 90°, 45°, 30°, 10°, 1°), however, nothing prevents the user from selecting any other step value.
If apart from the checkbox Fix edge angle another box For first edge is also checked, when adding the first edge of the feature in a similar way the angle between this edge and the horizontal coordinate axis is fixed.
When adding area features a checkbox Fix on completion is present on page “Input”. If it is checked, when adding some edge the system tries to select the edge length so that the angle between this edge and the line completing the polygon was divisible by the fixation step. However, unlike fixation of the angle between edges, the system is not always able to guarantee fixation on completion since it can correct the edge length only within limited range.
The modes of angle fixation do not affect editing of the existing features.
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