November 08, 2006

Creating AutoCAD 3D Polylines from GIS Features

My youngest daughter, Evie, turned 3 last week and to celebrate I can talk about 3D things.

How do you create a 3D Line in AutoCAD using the ArcInfo EXPORT TO CAD geoprocessing tool?
In Microstation the default linear element that gets created by the EXPORT TO CAD tool is a complex line string, which for 3D Microstation files is already a 3D element. In AutoCAD there are different types of complex lines; the Polyline, the Lightweight Polyline and the 3D Polyline. The EXPORT to CAD tool by default creates lightweight polylines.
Therefore if you have 3D linear features in ArcGIS and you’d like them to be 3D linear features in AutoCAD you have to override the default behavior of the EXPORT TO CAD tool by including a field in the exported feature classes’ attribute table called [CADType] and then populate that field with the string ‘3D POLYLINE’ for all the linear feature that you want to be created as 3D Polylines in AutoCAD.

For more information on creating CAD data in ArcGIS you can view several linked articles found in the ESRI Knowledge Base.

November 03, 2006

CAD Property Field Name Changes

Hannah, Hannah, Hannah, Hannah, …oh my!

Oh no!... get ready for another season of GIS and CAD basketball metaphors and anecdotes. Its that time of year again when I breakout the basketball sneakers and my sweat suit and mix it up on the court with a bunch of Jr. High School girls as their assistant coach. In this school of around 50 students, the freshman girls basketball team hopefuls that assembled for the first team practice this week, 4 of the 14 girls are named Hannah. If you add to those to my daughter Holly and, Heidi we’ve got a lot of H’s.

We quickly needed to rename them all. Now Smitty, Scooby, Chip and Tweedles are getting used to their new names.

Here are a couple of ArcGIS CAD feature attribute property name changes you can look forward to in ArcGIS 9.2. These changes made in the ArcGIS CAD feature attribute table property field names were done to make them consistent with the geoprocessing tools, especially the field name driven features of the EXPORT TO CAD geoprocessing tool. Where meaningful both the old and new names can now be used with EXPORT TO CAD.

AutoCAD block names used to be stored in the field named TEXT. In ArcGIS 9.2 this field has been renamed to REFNAME, to more accurately reflect the scope of values that can be held in this field. Other entities values that might share this field share this field name are Microstation tag sets, attribute tags names, block attribute tags, and text values.

Both ROTATION and ANGLE can be used to denote the rotation angle of CAD entities and are recognized by the EXPORT TO CAD tool.

Another useful bit of renaming of fields comes by using the MAKE FEATURE LAYER field information parameter and also the MERGE tools field renaming capability. I can use existing field names and rename them as part of the operation of exporting data temporarily as in the case of the MAKE FEATURE LAYER tool, since it only make the change to the field name in memory. In the case of the MERGE tool I use the field renaming feature to make more meaning of the values in the CAD file, especilly if they correlate directly to a data field. This often occurs in a text value like REFNAME, TEXT, LAYER or even LINESTYLE.
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