Hello Everyone! As I said in tech tip #57, Mark's answer to this question was quite lengthy so I broke it up into four parts. This is Part 3 of 4. I attempted to make the "breaks" at logical points in the answer so a thought wasn't chopped midstream. I will keep the original question in each tip to help with orientation. Enjoy!!
An InRoads Designer asked for Mark's direction with this question :
Hi Mark, I know this is a tough question, but I'm trying to get my wits around how to do site grading with InRoads. Roadway work seems much more straightforward. Anything that you can do to point me in the right direction would be great!
Thanks,
- ASD (a struggling designer)
Here is the Zen Dude's response:
As a very broad orientation to site grading within InRoads, let's break down the site design work into two main parts:
- The limits of grading - This is the outer edge of the design surface.
- Interior grading - This refers to any grading work done within the bounds of the 'limit of grading'.
These two areas of the site design are obviously different for every site; however, they are always definable within the specifics of the scope of work.
Beyond the specifics of the design, there are basic concepts that have to be grasped relative to working with surfaces (DTMs) and doing site grading with InRoads. These might seem very basic, but they are the foundation to site design with InRoads, and if they are not fully understood then other higher-level applications of the software will be more challenging. Trust me on this one.
1) The InRoads surface model is a stand-alone file that contains all of the 3-dimensional project data (and be aware that InRoads cannot only store 'on grade' information but also above and below grade information like storm piping and overhead power lines).
2) The InRoads surface model (DTM) is independent from any CAD drawing. The CAD drawing may contain a display of the surface data but the DTM is not dependent upon, or directly linked to, any of the CAD file information. (Although InRoads does have recognition that it may have displayed those graphics.) From this item - do not assume that what you see in MicroStation is in the InRoads DTM.
3) An InRoads surface model starts with 3-dimensional project data that is defined by the designer and placed into the DTM surface by some appropriate method.
4) InRoads forms relationships amongst the 3D data found in the surface model. The relationship forming routine is called 'Triangulation' because it forms triangles as it connects the data and defines the associations between the data found in the surface model.
a. A triangle leg defines a straight linear grade from one 3D location to another. This is key to not only developing new grading but also in cleaning up inappropriate grading that can be generated by the data contained in the InRoads surface model.
5) 3D data can be placed into the InRoads surface model using a number of methods, some more complex than others. Most of the InRoads site layout tools (Design Surface) have a particular purpose and are intended to solve specific design problems while placing those 'solutions' into the surface model.
6) If you want to 'force' the grades to go from point A to point B a breakline must be added between point A and point B in the surface model.
7) The density of the DTM triangle network should be considered when building an InRoads surface model. Remember that the surface is supposed to be a 'simulated' model intended to accurately represent the existing or design condition; and sometimes engineering 'judgment' can come into play here. Really understanding the construction of the surface model relative to its triangles can help you determine an appropriate triangulation density, but another aspect of the best density of data is the subsequent display of the contours, and resulting drainage patterns. The value of adding information into the surface model is validated by viewing the results in the CAD drawing. Always verify that the results are what you wanted, and expected.
8) There are two types of contours within InRoads, input contours and output contours. Typically, contours are an 'output' or a 'created-on-the-fly' display that is developed from the InRoads surface model triangulation. Contours can also be used as input to assist in the construction of an InRoads surface. This particular issue is more relevant in those design environments that utilize hand-sketched contours as a basis for their new grading in areas such as landscaping, berms and golf courses.
Civilly yours,
-zen
Mark is not only a good teacher, but a good designer as well. Mark is both knowledgeable and clear in both the InRoads software and in the area of Road Design at ITD. He provides good and direct answers to questions and assists in developing solutions in the design process. He is a uniquely qualified individual. 
