Join Josh Modglin for an in-depth discussion in this video Grading criteria sets, part of Autodesk Civil 3D 2020 Essential Training.
- [Instructor] Whenever we being to grade, we may, in our mind, play out a lot of different criteria and scenarios. Or we might not even realize it. It's like riding a bike. But if you start to try to think about what you're doing, it almost becomes hard for you to do. We're answering: where are we going? And how are we going to get there? And so as we look at this cross section, let's play out those questions and answer them through this sample here, upon cross section.
Now, we're coming from the bottom of the pond. That's our base point. It's our starting point, and we are going to an absolute elevation of 737. How are we going to get there? At a slope of three to one. You see how we answer those two questions? Now let's go to the next section. We just have this little flat ledge here. Where are we going? We're going a distance of three feet.
How are we going to get there? It's probably going to be pretty flat. We may have some positive drainage, but the intent is that it's a flat ledge. We repeat: where are we going? An absolute elevation of 740. And we're going to get there with a slope of three to one. You see how this continues to repeat. So what Civil 3D has going on, is they have what's called a grading criteria, and it's part of a collection or set. It's kind of like a parts list, and in that grading criteria, those two questions are answered.
And so Civil 3D then will dynamically grade from a starting point, a feature line, and apply the answers to the two questions that we provide. And so we simply have to have that grading criteria setup, and it's like a style, like a parts list. So, some templates, including the one out of the box from Autodesk, has the grading criteria already setup. Let's create our own grading criteria, and again see how we answer those two questions, and that way when we begin to grade automatically using Civil 3D, we'll better understand what a grading criteria set is, and how to utilize it effectively.
So we're going to go to Civil 3D here, and we're going to open up our exercise file, using our quick access toolbar. We're going to open up drawing 13_01_GradingCriteriaSets. There's nothing in the drawing. We're simply going to go to our tool space, and under settings, we're going to scroll down, and you'll notice it's about the fifth item down: Grading. And it's got a sub folder called Grading Criteria Sets. There's already one there. But we're going to right click and we're going to create a new grading criteria set.
We're going to name this grading criteria set LinkedIn, and the intent of the grading criteria set is really just a collection. So we're just naming that collection, and inside that collection of LinkedIn, we're going to create some grading criteria. Now as we mentioned at the beginning, we're going to be grading from the bottom of the pond to an absolute elevation, and we're getting there with a slope of three to one. So our very first criteria, we're going to name 3:1 to Elevation.
So what's found in the criteria tab are the answers to those two questions. Where are we going? Are we going a distance? Are we going to tie into an existing surface? Are we going to an absolute elevation, or a relative elevation? Two feet above the feature line that we've selected. In this case, we're going to an absolute elevation. However, there were two criterias that were very similar. Three to one to 737 and three to one to 740.
And so we're going to leave this at zero, and then allow the software to prompt us on what the elevation is. Because this is going to be unlocked, it will prompt us for the elevation. However, we did name it 3:1, so we're going to change this to 3:1, I only have to type in three because the ambient settings of the drawing settings know that slope equals run to rise. Now because I named this 3:1, I don't need to be prompted for the slopes here.
So, I've locked those down. And then how do we deal with the corners when you offset and you have a arc, and you've offset in toward the center of the arc, and the radius of that arc is five, and you've offset 10, you've passed the arc. And you've gone from having a PC and a PT with their own elevation along with potential elevation points along that arc, to having just one vertex. So how do you deal with that adjustments, interior corner overlap, they call it? And so we've just set the default that you used the average slope between all of the values there to establish the new value at that vertex.
So we go ahead and click OK, and we've created a criteria called 3:1 Elevation that we can use to get out of the pond to elevation 737, and to leave the flat ledge to get an elevation of 740. Speaking of flat ledge, let's go ahead and create that criteria. We're going to create a new one by right clicking on LinkedIn, and going to go to the Information tab and we're going to name this Flat Shoulder. Under the Criteria, where are we going? We're going a distance.
However, again, just like the flat ledge, we also have the top of our berm is a distance. And it's pretty much flat. So we can use this scenario for both of them, so we're going to leave the distance unlocked. Three feet for one, eight feet for another. However, we definitely don't want to have any type of slope. We're going to set it to a grade, and we could set this to zero, but I do want some positive grade back into the pond. So I'm going to to set that to 2%, but we did name it Flat and so the only thing we're going to be prompted for is how wide this flat shoulder is.
Click OK, and we've taken care of, again, two additional criterias that we run across in that pond. Let's look at our third, which was three to one, to the existing surface. So we're going to right click, choose New, come to Information tab and we'll name that 3:1 to Surface and in our criteria, where are we going? The answer is, we're going to a surface.
How are we going to get there? Well, it's going to first prompt us to figure out: do you think you're going to be in Cut First or Fill First? The reason being is this can be a very time consuming process. Imagine that even on a small lot, as you daylight on the exterior edges of your design, you could easily get close to a mile of daylight. And so it's trying to speed up the process. I do go ahead and lock this and just leave it at Cut First, and the reason being, by the time I figure out which one is probably the most, that I'm going to be mostly in Fill or mostly in Cut, the software could have run.
So I just go ahead and lock that. We're setting this to three to one, whether we're in Cut or Fill, and we did name it 3:1 to Surface so I lock those. We're using the average slope, so I lock that. So when I use this criteria, I won't be prompted to enter any values at all. It will simply daylight to the surface. That's where we're going. And how are we going to get there? At a slope of three to one. We've answered all the questions, and locked them so they're not available at a prompt, at the command line when we use this grading criteria.
So we have all our grading criteria set, we have a nice collection of available. We understand a little bit more about what's a available in this. Now we're going to use a different grading criteria set as we grade the pond that we saw in the beginning of this video, in our next exercise.
- Navigating the Civil 3D interface
- Using point groups and description keys
- Importing survey data
- Managing figures
- Creating and analyzing surfaces
- Creating parcels
- Working with alignments
- Working with profiles and profile views
- Creating basic and advanced corridors
- Using an intersection object
- Making sample lines, cross-sections, and section views
- Creating a pipe network
- Creating and editing feature lines
- Creating and editing grading objects
- Creating view frames and sheets