From the Ground Up - Autodesk Civil Blog

How to create a flood plain - Tip and Trick

Ok, this is turning into a brain dump week So to do this little technique we merely use a cut and fill method to find out where a given level would intersect the ground.Step 1Draw a rectangle over your surface Step 2Convert the rectangle to a feature line and assign it a constant level/elevation of what you require to check against Step 3Create a surface from this rectangle Step 4Create a volume tin surface comparing the ground to this flat surface Step 5Create a style which just shows a user contour only and set the layer, colour, lineweight etc and apply this to your volume surface Step 6Click on the volume surface and its properties and click on the analysis tabChoose user contour, set one range and enter the value 0Click Apply Step 7The line drawn is where the flood level intersects the ground surface Step 8 - ChangeSo by turning on the rebuild automatic to your flood level surface and the volume surface, you can now select your featureline and adjust its level/elevation and watch how the flood extents take affect.Fun, or scary depending if you live near the area affected!Step 8 - VisualisationOf course its nice to have a pretty picture of your work, so all we need to do now is restrict the flood surface to the contour line being drawn.This you will need to extract the contour line from the volume surface, so select the volume surface contour line, extract objects and ok to the contour line. Add this polyline to your flood level surface as a non destructive outer boundary.(NOTE you may need to close the boundary like mine as the 0 level went outside my surface limits.) Then using the techniques explained in my earlier post on boundaries and holes you can create a copy of your ground to cut a hole out of. Link to postThis will put your volume surface out of date also as you are affecting the surface it is based on, again make a copy of it if you prefer with the paste edit option.Then of course set render materials to suit Jack Strongitharm

9/3/2010 7:53:36 AM

Using Surface Boundaries for Grading Tasks - Tip and Trick

Its like catching a bus sometimes, you wait for one and three come at the same time!Anyway, carrying on from the last two tips this week, lets look on how to use those boundaries for grading tasks also.I find a lot that users are wanting to use corridors to form ditches and other features at the side of their roads and other formations they are designing and over complicating the task by try to use corridors for everything.I quite often will use a corridor to create a surface or linework to do the maths and then butcher it to suit my purposes. So in this airport case I just wanted to grade from the runways and taxiways down to form a basic basin.With the corridors crossing with junctions etc, the best way is to simply use the inner surface boundary of the pavements and grade from them.Obviously the boundary is static, but easy enough to do an update if you need. So I first recommend carrying out a weed on the boundary, with us forming the boundary in an unconventional way.This you find in the modify tab and feature lines. (You can use this command on polylines also) Then using either the Civil 3D grading or in my case just the 3D stepped offset to create an offset of a distance and slopeStepped Offset is again in the modify tab and feature lines.This is the only way to offset 3d polylines in AutoCAD, i,e, not in standard AutoCAD. Then just create your surface from breaklines and you are done Jack Strongitharm

9/2/2010 11:11:07 AM

Page 1 2 3 4 5

From the Ground Up Autodesk Civil Blog

From the Ground Up
Autodesk Civil Blog