March 14, 2007

Working with Text: Part 2

ArcGIS Labels and Annotation

I really enjoy the way a small sailboat has gives me a feeling of being directly connected to the water, the air and the craft itself. More than just floating or paddling through the water, a sailboat allows me to use natural forces against one another for my gain. I can float if I want to, but generally I want to be going places.

In ArcGIS text can just float on its own, or it can be driven by features. In the most general terms GIS annotation could include any map text, marginalia, and displayed attributes. More explicitly there are different forms of text in ArcGIS using different data constructs. Any ArcGIS feature can have feature labels that are generated from attributes. Unlike ArcGIS feature labels ArcGIS annotation features are features in their own right. One higher level of annotation is that geometric features can have annotation features that belong to them, this is called feature-linked annotation. Or, text can be displayed as simple graphic text, that is not a feature, and not linked to other features, this form is the most similar to CAD text.

In ArcMap any GIS feature can have a displayed feature label. This feature labels can be toggled on an off as a property of the ArcMap label. The label can have justification and font properties and its text value is derived from the attributes of the feature layer. Labels are regenerated from the feature's attributes and generally are placed by a labeling engine. The default labeling engine has some simple options to avoid overlapping labels and the alike. An example of a high-end professional labeling engine would be something like ArcGIS’s Maplex labeling extension that uses sophisticated rules-based label placement algorithms. ArcGIS feature labels can be converted into ArcGIS annotation feature classes.

Another form of text, ArcGIS geodatabase annotation feature classes, have their own geometry, attributes and set of justification methods. Unlike feature labels that are placed on-the-fly using an engine from other feature layers’ attributes. Annotation features are persisted and stored in a feature class, along with their position and other display properties. Annotation features can be independent or they can be linked to other feature layers. Feature-inked Annotation derives its text value from the attributes of the linked feature class (like the diameter of a pipe, or name of a street), but retains its own separate geometry and properties (for example: a specific rotation or position on a map.)

You can learn more about ArcGIS text from the ArcGIS online help.

ArcGIS feature labels cannot be exported using for example the Export to CAD tool, but the tool does export geodatabase annotation features, which I can generate from feature labels in ArcMap.

The ArcGIS CAD feature class that is generated in memory when a CAD file is used by ArcGIS, is yet another form of text. The CAD annotation feature class is implemented as a file-based
annotation. This type of annotation is more akin to the legacy ArcInfo Coverage Annotation feature classes. Suffice to say it is old-school and lacks many of the nifty functionality available with the invent of geodatabase annotation feature classes.

There is a tool to convert file-based annotation and CAD annotation feature classes to geodatabase style annotation. This tool is called the Import CAD Annotation tool…


Anonymous Jeff Albee said...

I am working with CAD data (vector and text labels), and want to convert it to a Geodatabase with the text as attributes. Is there a preferred version of CAD that I should be working with to achieve this? Would AutoCAD Map be better/easier than 2004 or 2007? Thanks.

11:50 AM  
Blogger Don Kuehne said...

Text entities in CAD can be associated with vector features that they are closest two using the ArcMap spatial join function or the NEAR tool.

For POINT features it is easiest to create a block with attributes to associate visible labels with feature in ArcGIS since ArcGIS reads block attributes as POINT feature attributes.

If you have Autodesk Map exporting datat to a shapefile may be another way to go, but you certainly don't need Map to create text and lines in a CAD drawing that are usable in ArcGIS.

1:50 PM  
Anonymous Anonymous said...

I am working with CAD to GIS conversion. I am having block inserts with object data in CAD. If i export them as point, I get the object data. but I require the object data by exporting them as polygon. I could get the polygon features if i load the data from ArcCatalog but not getting the attributes.

Is there any way to get the attribute data with features as polygon?

6:37 PM  
Blogger Don Kuehne said...

I think we need to be a little careful with our terms here since some of the jargon has different meanings depending on if you are a in CAD or GIS. I will answer the question how I "think" you meant to ask it.

By Object Data I am assuming you are simply talking about GIS table attributes, and not AutoCAD Extended Entity data or its more advanced form "Object Data". There is no really good way to assign attributes to exported polygons. It works for points because you can use blocks with block attributes. There is no analagous CAD polygon object that supports attributes. I might suggest my series of articles on Exporting Attributed CAD Data:

9:17 AM  

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