Existing surface data can come from a variety of sources. It can come from the Land Surveyor in the form of a COGO points, from an Aerial topo in the form of Contour data, from a DEM (Digital Elevation Model) file, or even from Google Earth data. The focus of this lesson is to take data that was received from the Land Surveyor and turn it into a surface model that can be edited, labeled, and used for engineering design. After we create our existing conditions and the designers create their finished surface model, we will explore how to run volume calculations and thematic mapping for cut and fill areas.
One of the most common forms of data used to build a surface is COGO (Coordinate Geometry) point data. The data with which we are working to generate our surface is many thousands of existing ground spot shots. We have a limit of work line that we are going to work with; we will build our surface only within the limits of our work line. In order to accomplish this task, we will be working with Civil 3D 2009 and using a Data Clip boundary.
The steps that need to be taken to accomplish the above tasks begin with the creation of a new drawing, starting with your company's drawing template file that contains all of the necessary Object, Label, Table, and Command Settings. Next you will need to create a new surface and give it a name and style; this can be done in your Prospector tab on your Toolspace: right-click on Surfaces and select Create Surface. This will allow you to create a TIN surface. Name your surface and select an object style, as shown below.
Once you have created the "shell" for your surface, we can then create a Data Clip boundary to limit the amount of data that we bring in for our surface, thus keeping our drawing file as small as possible. Please note that the Data Clip boundary must be added to your surface prior to adding any other data such as Point Files, Point Groups, Contours, or Breaklines. The boundary line must also be drawn prior to creating the data clip; the command does not allow you to draw the polyline "on the fly." Expand your surfaces collection: Expand Definition --> Right-click on Boundaries --> Select Add (see below).
Once you have added your Data Clip boundary to your surface, you can then import the data from which you will build your surface.
Now we are going to build our surface from point files that are stored in a separate location. This method will use the data in the external text to build your surface, thus keeping your drawing file small by not importing the points directly into your drawing file. Under the Surfaces collection --> Definition, right-click on Point files and select multiple point files by using the + key with Shift and or Ctrl (see below).
Another way to build a surface in AutoCAD® Civil 3D® from survey data is to import the text files directly into Civil 3D. Group your point data and build a surface out of points. In this next example, we will import a PNEZD text file into Civil 3D, create point groups to organize our data, and build our surface model out of our organized data.
We are going to start by importing our points directly into Civil 3D by going to the Points pull-down menu --> Import/Export Points --> Import Points. After your points are inserted into your drawing we can now create groups to isolate what data we want to use to build our surface. In fact, you can create point groups and save them into a template file. Then when you insert in your point data, the groups will automatically populate with the points.
In order to create a point group, you need to head over to your Prospector tab, right-click on Point Groups collection and select New. Within the Point Group Properties dialog box on the Information tab, you have the ability to give your group a name and assign a point object and point label style to your group. Next you need to select the Include tab to assign which point properties will be included in your group. You have the ability to create a point group using Numbers, Elevations, Names, Raw Descriptions, and Full Descriptions Matching. Note: When using name or description matching, you do not need to worry about case-sensitive matching (see below).
After your points are grouped, you can then create a surface and add your data to it. Follow the previous steps to create a shell for your surface. Next you want to expand your Surface collection, expand Definition, and right-click on Point Groups to add your newly created point groups to build your surface (Hint: Use Shift and/or Ctrl to select more than one group at a time).
Now on to Surface Editing commands! After you have created your surface, view it as a TIN and Points; you can put it in an Isometric view in order to find any spikes or erroneous TIN points. See picture below for points that will be edited.
Under the Definition area of the surface, right-click on Edits to display all of the types of edits that can be made on your surface object (see below).
For this particular surface we use the Modify Point surface editing tool to modify the two spikes shown in the picture above. Before modifying these points, you must first either get with the Surveyor who collected your data to find out what the true existing elevations should have been, or you can analyze your surface and interpolate what the elevations at these points should be. Note: In order to use any of the Point edit surface tools, your surface style MUST have TIN Points set to "On."
Once you have your surface fully edited, it is time to add in your Contour Labels. You must first set your surface style to display the contours at the desired interval. Next you want to go to your Surfaces pull-down menu --> Add Surface Labels --> Add Surface Labels. In this dialog box, we will use a label type of Contour – Multiple, as shown below.
The great thing about the Add Labels dialog box is that it is consistent whether you are labeling a Surface, Pipes, Profiles, or any of the Civil 3D Objects.
The use of expressions and reference text surface labels inside of Civil 3D can be extremely powerful in labeling TC-FL elevations. The use of expressions allows you to label the TC and subtract 0.5' for the FL of a 6" curb. You can also label EG-FG information with the use of reference text, adding a surface spot elevation for two surfaces included into one label. See below for the use of both expressions and reference text labels for a precise grading plan. Both of the labels used were surface spot elevation labels types.
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Melanie Santer is an application engineer for U.S. CAD, Inc., a large western-region reseller and Autodesk Authorized Training Center (ATC). Melanie has more than five years experience in the civil engineering industry, more than two years of practical field survey experience, and more than two years of land development/design experience on large commercial and industrial sites. Since 2005, Melanie has taught hundreds of public and custom classes using AutoCAD, Land Development Desktop, and Civil 3D and has been recently hired as an instructor at a local university. She is currently assisting more than 40 firms in California implement Civil 3D into their production environment.
