Section markers are primarily used to nominate where cross sections are to be generated along a primary alignment. They can be used to display distances and chainages along alignments at regular intervals. Also a section marker can be placed at any required chainage to enable an elevation to be generated at a required point in a long section.
There are two types of section markers, fixed and floating. If a section marker is placed at a key point it automatically becomes a fixed section marker, otherwise it becomes a floating section marker.
The only difference between the fixed and floating section markers is how they react when the alignment they are attached to is edited. If a key point has a section marker attached to it and the key point is moved, the section marker will be moved with the key point as it is fixed to the key point. If a section marker is floating it will always maintain its distance, from the start, along the alignment. This may have side effects that are not always obvious when editing points in an alignment. For example, if a point was deleted within an alignment this would probably reduce the length of the alignment. This in turn would have the effect of "moving" the floating section markers past the deleted point further along the alignment as they try and maintain their distance. This may result in some section markers being pushed off the end of the alignment and consequently deleted. It may also result in floating section markers being moved to the other side of fixed section markers as the fixed section markers will stay attached to the key points. Likewise the distance on all the fixed section markers, past the deleted point, will be reduced by an equal amount.
Section markers also directly control cross sections. If a section marker is deleted or moved, any cross sections generated at this section marker will be deleted.
Section markers are objects in their own right and as such have symbols, sizes and directions that can be set for each individual section marker. Note that the symbol direction does not influence the direction of the cross section generated at the section marker. Cross sections are always generated at right angles to the primary alignment, or they bisect the angle subtended at the key point.
Creating section markers based upon regular chainage intervals needs to be performed in the distance configuration you finally want to work in. For instance, if you are working in grid distances and section markers are created every 20.000 metres, they will appear at 20.000, 40.000, 60.000 etc. If the system is now configured for ground distances the values will change to reflect the ground distances between the section markers and may look something like 20.058, 40.114, 60.180 etc. So, if it was necessary to set these section markers out in the field at every 20.000 of ground distance, then the section markers should have been created initially in ground.