The Line Formation dimension, fixed as LF=, allows you to create more complex constructs within line segments based upon directions and distances. Basically, the dimension is a sequence of pairs of numbers with the first giving a direction indicator relative to the last direction and the second defining the distance. Each of the numbers in the dimensions string should be separated with a comma, a space, a slash or a hash character.
The diagram below shows what the value of the first number, or direction, means. If the value is -2, the distance will be applied to the left of the current point perpendicular to the current direction. If the value is -1, the distance will be applied 45º to the left of the current direction, or half-left. If the value is 0, the distance will be applied in the same direction. If the value is 1, the value will be applied 45º to the right of the current direction, or half-right. If the value is 2, the distance will be applied to the right of the current point perpendicular to the current direction.
The diagram below shows various ways that the line formation dimension can be used to construct additional detail in line features.
The first segment, between points 1 and 2, has a squared construct starting 5 along from point 1 in the direction of point2. Since point 1 is the first point on the feature, the start direction is assumed to be the direction between points 1 and 2. The dimension assigned to point 1 is LF=5,-2,5,2,5,2,5. This reads as go along 5m, then go left 5m and then go right 5m twice. Once the end of the construct is reached, the line will then be joined to the point 2 of the feature. Note that this dimension has an odd number of values and, therefore, n4ce assumes the first value is a distance in the direction of the segment, effectively changing the dimension to be LF=0,5,-2,5,2,5,2,5.
The second segment, between points 2 and 3, has an octagonal construct appended to its end. In this case, the dimension contains an odd number of values and, therefore, the first value is assumed to be a distance along and the start direction is the direction of the segment from 2 to 3. The dimension assigned to point 3 to create this is LF=1,2,1.25,-1,2.5,-1,2.5,-1,2.5,-1,1.25. This reads as go along 1m then go right 1.25m. After this, go half-left 2.5m 3 times and finally go half left 1.25m. Once the last point has been constructed, it is then joined to point 4.
The third segment, between points 3 and 4, has another squared construct appended to the end of it. In this case the dimension contains an even number of values and so the initial direction is assumed to be the direction of the previous segment. The dimension assigned to point 4 is LF=-2,5,2,5,2,5. This read as go left 5m and then go right 5m twice. Once the last point has been constructed, it is then joined to point 5.
There is no dimension assigned to point 5 but the construct after point 6 shows that line formations can be used to extend the end of line features. In this case, the start direction is the direction of the segment between points 5 and 6. The dimension assigned to point 6 is LF=-2,5,-2,5,2,5,-1,5. If you wish to extend the segment 5 to 6, you should insert the value of the extension as the first value in the dimension string.
If you are generating a construct from the last point of a closed feature, the final point of the construct is joined to the first point of the feature.