Ask A Cartographer

Recommended projection for creating annotation.

August 05 2007 | 0 comments
Categories: ArcGIS Methods, Data Modeling

Creating new annotation in ArcMap requires you to be in a un-projected environment or else the
annotation will not display. Can you explain the reason for this. I suspect it has to do with the geometry properties of annotation, is this correct?

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Thanks for your response, I think it certainly helps with how we understand annotation. The project I’m involved with involves supplying two databases, one in geographic and one in utm for map production.

The one in UTM we capture the annotation for while the data frame is still in geographic, we then place the annotation after changing it to the correct UTM projection.

My question stems from the situation we find when having to add additional annotation later ie. adding using the key-in and place tool. The annotation is placed but cannot be seen unless the data frame is changed back to geographic. Obviously this is impractical and we have got around it by copying and altering existing annotation, which seems to work.

I’m worried we are missing some fundamental understanding of how our data should be managed here.

Mapping Center Answer:

The way you describe understanding how annotation works relative to coordinate systems isn’t quite the way it really works.

First, annotation can work in any projected or geographic coordinate system. However, if you want it to work for your map, which may be using a specific projected coordinate system, the annotation must be stored using your map’s coordinate system.

For example, if I want to make map that shows all of North America as my extent, I might use an Alber’s Equal Area Conic projection for my map. So I would set that as my data frame’s coordinate system. As a matter of best practice, I would also create a new geodatabase for my map’s data and project all my data to that same Alber’s Equal Area Conic projection. First that makes my data draw faster since it won’t have to be projected on the fly. Second, and more importantly for what you asked, that sets up a location where I can create my annotation so that it will be stored in the same coordinate system as my data and most importantly my map.

You can certainly expect data (points, lines, polygons, and rasters) to project on the fly and look acceptable; however, annotation probably will not look good. Annotation depends on a number of additional factors, including whether it is stacked or uses a horizontal, straight, or curved baseline to determine how good it will look in another projection; results can almost good; where character spacing may seem a little off, or really bad. The one other item that can affect how annotation looks is the reference scale it was created to work at; if that reference scale does not match your map’s current reference scale, it can look quite bad as well. You can sometimes mitigate some of these effects in order to get a little more use out of your annotation by using symbol substitution (on the annotation layer’s symbology tab). Though, it is very difficult to overcome mismatches in reference scale or kerning differences between fonts.

Hopefully that will get you a good bit further along, let me know if you’ve got more questions. This is an area where I don’t think our documentation is particularly good, at least in terms of a top-down story, so I’d like to hear whether this helps so I can push on our documentation team to assemble something more useful.

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The critical thing here is that you need to create your annotation after changing the data frame’s projection to UTM (rather than before), and you must store the annotation in a feature dataset is defined to use your UTM projection.

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