Getting Started

 

It seems like no matter what we do in life; "Getting Started" is the hardest part. Whether we are at our job, home working on a project, dieting, exercise or writing a blog, getting started is the hardest part.

Perhaps it is the fear of the unknown or simply not being comfortable with the task, if you're like me,  you avoid things you haven't tried.

There are a lot of people out there totally new to PowerCivil. My first post "Intelligent Design" was to make a case for why we need a tool like PowerCivil. My intent with this post is to outline a process and drawn similarities to your previous work flow.

Before we begin, we will make some assumptions:

  • 1. You have PowerCivil and have it installed and licensed.
  • 2. You know how to create a new file using a seed file. Or you have an existing file DGN or DWG and want to use it to begin.
  • 3. You can create a line or maybe more using Microstation

 

The Process

 

My primary goal as a designer was to take an existing site layout; draft a design representing the new use of the site; layout or design storm sewers, sanitary sewers, and potable water; and produce plans and reports.

The process in PowerCivil is basically the same as above. However, if we don't know the tools and are not familiar with the terminology and the process, we are set up for failure.

In a nut shell the process looks like this:

•1.      Begin with Existing Conditions

•2.      Create a Model (3 dimensional surface representing the design)

•3.      Create drainage, and water, and sewer projects

•4.      Create plan sets

Amazingly the CIVIL menu reflects this process

Step One - Existing Conditions

 

Creating an Existing Conditions site plan, or more importantly for our process, a TIN (Triangulated Irregular Network) representing the existing site can be divided into two categories:

  • 1. Create from the actual surveyed field collected data (Civil > Survey >DTM)
  • 2. Create using the DTM menu ( Civil > DTM )

Survey DTM- A TIN is created from survey data by triangulating the points and chains in the survey project. We can further control how the points are included in the TIN by setting up our SMD (Survey Management Database) features DTM control. This function allows us to control how a point or chain is stored in the TIN.

DTM - The DTM menu allows us to build TINs from a variety of sources. These would include :

  • Graphics
  • ASCII (txt)
  • DEM (Digital Elevation Model)
  • LIDAR (LIght Detection And Ranging)
  • Land XML

Within both the survey or the DTM tool there are tools and processes that allow us to to create the surface we need to move forward. Powerful editing and manipulation tools give us the ability to create surfaces where other programs will fall short. 

The process for creating the basic TIN is a 2 step process:

  • 1. Extract
  • 2. Build Triangles

Unfortunately, life isn't always this simple. Graphics produced in DWG format may be locked or exploded. This would require additional steps to unlock, Join the exploded contours, or  thin the number of vertices.

Further complicating this process could be crossing contours, or contours with no Z component.  While we can work with this data it introduces more steps to the process.

Information on how to use these tools can be found in the Help (F1) menu inside PowerCivil along with "Watch It" links to videos on the tools. Additionally, there are basic training videos on http://www.powercivil.com/

Fig Above shows a surface created from SONAR Data. This data included over 15 million points. An algorythim disigned for LIDAR filtered the points maintaining accuracy to a more managable 1.6 million points.

Step Two - Create A Model

 

Up to this point getting our existing surface TIN created has been much of what we are used to. Many other programs create a TIN or DTM. In PowerCivil, we will now create a MODEL, a Dynamic, living breathing three dimensional surface of our proposed design.

Well, OK maybe I'm being a bit dramatic, it really doesn't breathe. The process is actually simple, we just changed some terminology. Before we outline how the Model is created and works, let's review the way we used to create that finished grade surface.

A sample workflow of other popular software:

•1.       Create a DTM representing existing ground "EG"

•2.       Place points at critical locations, these points are then assigned a Z component

•3.       Triangulate points, specify side slopes

•4.       Stitch (merge) the new surface into the EG surface to create a new surface

•5.       Repeat this process adding subsequent surfaces

The problem with this method is we are unable to create a object using a relationship. Example: perhaps we need to keep handicap accessable parking at a specific slope from the front entrance of a commercial building. Additionally placement of points alone cannot model surfaces to the same degree of accuracy as lines and arcs.

Other problems arise when we need to make changes to this surface. These changes can require rebuilding of the entire surface for a minor change.

Site Modeler

As you see above the Finish Grade (FG) surface is usually a compilation of DTMs.

As my friend Michael Gilham (AKA: Mr. PowerCivil) once told me, "Site Modeler builds TINs". There it is, in a nutshell, the secret has finally been revealed.

Lets pull it apart a piece at a time to further unravel this Site Modeler magic.

  • 1. First create a project (.GSF). The project will link to the DGN or DWG design.
  • a. We will need to establish the project preferences. These will allow it to display according to our company standards.
  • 2. Create a Model by simply giving it a name.
  • a. A project can contain multiple models, each model will contain a minimum of one surface (object) but in theory can have an unlimited number of objects.
  • 3. Objects (surface TINS) are created by horizontally locating CAD graphics then using the modeler "Add Elements" tools to assign a Z component to the graphics. There is no limit to the numbers of CAD graphics (elements) used in a object.

The good part is the entire process outlines in the 3 steps above has a Wizard to walk us right through it to the point we are ready to begin designing our new surfaces (Objects).

Dynamic Objects

 

You may be wondering, why not just call the objects DTMs like everyone else? What is all this talk of objects?

Now I wasn't in Jays head when he began naming things but here is where we are different.

The objects we create are basically free floating TINs. These objects tie to our base object (normally EG) using a slope we specify (3:1 by default). When two or more object surfaces intersect one another, the objects tie to each other and also to the EG surface. The order that they merge together is determined by a list FIFO (First In First Out)

Because these objects are in a site model project they remain "Dynamic". We can write the graphics representing the proposed grade at any given time and keep our proposed grading project in tact. This functionality leads to real productivity advantages allowing us to instantly update our site model.

 

Where Do We Go From Here?

 

Future posts will deal with and resolve issues from users both past and present. Stay tuned!