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AutoCAD

Translating Data with Civil 3D, Part 1 (CAD Clinic: Civil 3D Tutorial)

31 Dec, 2006 By: Mike Choquette

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Data exchange skills for Civil 3D users.

Even though Civil 3D 2007 contains new Survey tools, many Civil 3D users still must exchange data with outside consultants for surveying and design services, as well as to collaborate with other offices on shared projects. Many companies also have legacy project data they would like to bring into Civil 3D. Currently, Civil 3D has many options for translating data to and from other civil/survey applications, as well as from one file server, Civil 3D drawing or Vault project to another. We will discuss this topic in depth in this and the next two Cad Clinic columns.

What Is Civil/Survey Data?
Have you ever received a drawing file from someone using Autodesk Land Desktop? Did they send you only the drawing file? While that drawing may contain graphics of points, alignments, profiles and so on, the drawing file itself doesn't contain the survey and design data those graphics reference in the Land Desktop project. For example, you may have surface TIN lines present in a drawing, but without the original project folder you don't have enough information to create contours, perform volume calculations, or reference it as a roadway existing ground surface. To perform functions like these you will have to first re-create the surface from those TIN lines. This kind of re-creation of data is usually time-consuming and error-prone. You can often avoid it by transferring drawing files along with the data referenced by them.

Keep in mind that Civil 3D does, in fact, keep this intelligence in its drawings (with a few exceptions such as survey databases). In many cases this means that you can send someone your drawings (or a copy of them) and they can pick up right where you left off in Civil 3D without any additional steps. If someone else needs to work on your drawings using another civil/survey application, you or the recipient may want to follow one of the processes listed below to make sure the design data is available.

LandXML
LandXML, the gold standard of data transfer in the civil/survey industry, is one of many generic data formats gaining acceptance in a number of industries (XML stands for extensible markup language). LandXML's internal configuration was agreed upon by a consortium of major civil/survey product manufacturers (including Autodesk), as well as government agencies, colleges and universities. As of this writing, all of the major competitive products of Land Desktop and Civil 3D, as well as many third-party GPS, survey and design applications, all support LandXML. What this means is that translating your data between applications should now be easier than ever. Among other features, LandXML is unit-intelligent, which means that its data can be translated from its native unit format (imperial or metric) to the current Civil 3D drawing unit on import. LandXML data files also make excellent archives of civil/survey data that can be created at any time in the design process. In Civil 3D 2007, you can create a LandXML data file from the File / Export / Export to LandXML command. The dialog box that appears prompts you to choose the objects you want to include in the LandXML data file through a tree view (shown below). You can also pick items directly from the drawing, if that's more convenient. LandXML files created by Civil 3D 2007 are also able to include pipe networks.

Keep in mind that when selecting a point object, its entire point group is selected for export. If a point exists in more than one group, the group listed highest in the point group display order is chosen (this display order can be adjusted by right-clicking on the Point Group collection in the Prospector and choosing Properties). Note also that exporting a Corridor will add any alignments, profiles and associated corridor surfaces to the LandXML file, but the corridor definition itself is not included.

When exporting LandXML files from Land Desktop (not Civil 3D), you should carefully look over your export data options (go to Projects / Export LandXML and choose the Data button). One of these includes a setting that by default describes your data as International Feet (when working in imperial drawings). This is problematic if you're working in U.S. Survey Feet instead, so be sure to change that setting if necessary.

You can import LandXML data into Civil 3D through the File / Import / Import LandXML Data command. In Land Desktop, use Projects / Import LandXML. In Civil 3D you have several import options, including the ability to automatically translate from U.S. Survey Feet to International Feet if desired. This option is disabled by default.

The Import LandXML command provides another tree view very similar to the one used in the Export command. Users are free to turn on checkboxes for only the data they wish to include in the current drawing. For more information about LandXML and its schema, please visit www.landxml.org.

Transferring Data
During our introduction to this important topic, we discussed what is meant by the term "Civil and Survey Data," as well as the most powerful and flexible way to transfer it: LandXML. In the following two Civil 3D CAD Clinic columns we'll discuss other data transfer methods, including direct import from and export to Land Desktop projects, methods of transferring Survey data from data collectors, and how to export Vault project files, as well as other Import and Export commands that relate to Civil 3D points and surfaces.