I am attempting to construct ‘as built’ flood control embankments into a DEM using information listed in a GIS layer of embankment centrelines. My purpose is to then subtract high resolution LiDAR of the same embankment from the ‘as built’ model to determine how and where the real world embankment deviates from the original design. We can use this information to identify defects and to assess the approximate volume of material needed to rectify the design.
I have got a fair bit of the way in M9, but need a bit of help with the next step which is to derive a DEM representation of the embankment slope away from the crest edge line (supplied). Within the dataset, the embankment slope is provided as a gradient rise per meter [BNK_SLOPE_GRAD_M_M] (see attribute list below).
To complicate matters, crest height of an embankment can vary along its length and is defined in the source dataset by crest a start and end attribute ([CREST_START], [CREST_END]). This means that the slope DEM needs to be derived for each segment along the embankment length to accommodate the varying crest heights ([BANK_HT]).
Embankments are also commonly asymmetrical in cross-section with a different bank slope for each side (See Clipboard-1 image for embankment cross-section schematic). I did have a method to produce a user defined DEM slope accounting for change in crest elevation on either side of a line in M8, but I can’t locate it at the moment. Ideally I would like to produce the specified DEM slope on one side of the line, but it doesn’t matter if it is on both sides initially as I can mask it later.
I want to achieve this in M9 for performance which has now overtaken M8 as my GIS of choice. I have had a couple of cracks at achieving this first in vector mode with line spacings and heights to achieve the correct slope when joined to the DEM, but my attempts didn’t deal with sharp bends in the embankment (See Clipboard-2 image)
If anyone is able to offer any suggestions of how to go about this in M9, I would be very grateful.
[BRANCH]Segment index for the embankment
[MAXID]The maximum segment index for the embankment
[CREST_M]The width of the crest of the embankment (not needed for this part)
[CREST_START]The height of the embankment crest at segment index start (0)
[CREST_END]The height of the embankment crest at segment index end (309)
[BNK_SLOPE_GRAD_M_M] The gradient of the slope in rise (m) per meter
[BANK_HT]The calculated segment crest height
M9 FORUM DATA.mxb