A recent question from a customer:
How does the module compute a slope chainage for ground shots?
Slope chainage appears to be generated based on reference to the alignment (start reference 0+00….etc) However does it use the slope distances obtained from measured shots as absolute/only value for the slope chainages or is it a mixture of other parameters?
What is the needed distances of connection between the as-built pipeline vs alignment to make slope chainage generated from the module viable?
An alignment can be defined in Pipeline options, this alignment would typically be the design alignment - or something as close as possible to the design alignment.
From this design alignment we can compute stationing - but the stationing is obviously just a preliminary stationing. True stationing can only be computed from the start of the pipeline using asbuilt survey measurements on the pipeline. On any particular survey day it is highly unlikely that one data collector has all the asbuilt survey points in the job, so we cannot compute true stationing, all we can really do is compute approximate stationing from the preliminary alignment. True stationing can only really be computed in the office using all the asbuilt survey data.
When the Slope stationing check box is selected stationing is computed on the slope distance instead of the horizontal distance. In hilly terrain, slope stationing gives a better representation of true stationing than horizontal stationing.
Note – Slope stationing can only be computed if there is a valid vertical alignment defined along with the horizontal alignment.