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Cofrin Center for Biodiversity

•  WATCHOUTS AND USER NOTES  •

When we learn something that might be useful down the road we try to capture it in a way that we can actually get back to it when the time comes.

Coordinate Systems and ArcGIS Software
The Esri software does an amazing job of sorting out the coordinate system mess behind the scenes. But it's not completely automatic. There are lots of obscure factoids and odd situations that require the operator to jump in and tweak things:

  • The Data Frame Coordinate System page on the Biodiversity Center website pulls together info on a topic that is a challenge for people just learning the ArcMap software

Cartography
The cartography tools in ArcGIS are very powerful, but it takes a long time to learn how to use them effectively. We've tried to pull together some tips and shortcups to help novices bypass some of the learning curve:

  • Our Scalebars In ArcMap page includes a quick recipe for a nice-looking scalebar
  • Make sure you've attached the scale bar to the correct Data Frame
  • Don't forget that the scale bar is dynamically linked to the Data Frame. It will grow and shrink as you zoom in and out. That means your map should be at its final scale when you make the various settings
  • Never use the "Group" command to combine a scale bar with other graphic elements. If you do, the scale bar will lose one of its most important properties – its freedom to resize itself when you zoom in or out.

Scalebar Shortcut
When you use the Insert – Scale Bar command you wind up with a lot of options. Trying to figure out the right settings to produce a nice-looking and informative scalebar can be complicated and time consuming and you still might wind up with a mediocre result. If you work through the following steps, you can eliminate some of the hassle and you should wind up with a pretty nice scalebar. Start by choosing Alternating Scale Bar 1 from the Scale Bar Selector.

Adjust "Scale and Units" Properties as follows and in the order shown:

  • If your audience expects English units, set "Division Units" to "Feet" or "Miles".
  • If your audience expects International units, set "Division Units" to "Meters" or "Kilometers"
  • Set "Label Position" to "below center"
  • Set "Number of subdivisions:" to zero
  • Uncheck the "Show one division before zero" checkbox
  • Set "When resizing…" to "Adjust Width"
  • Experiment with "Division value:" and "Number of Divisions:" until you get something that makes sense and looks good.
  • After you are completely satisfied with the layout of the scalebar, reset "Number of subdivisions:" to a value that helps the audience measure shorter distances.

Adjust "Numbers and Marks" Properties as follows:

  • Set "Numbers – Frequency:" to "divisions" unless you decide that one of the other settings conveys important information to the audience.

Label Expressions
Using the ArcMap Labels property to add information to an on-screen map is often just a matter of telling the software to display one of a feature's attribute values adjacent to the feature. But it's possible to get a lot fancier:

  • Building label expressions, an article from the ArcGIS 10.1 section of Esri's ArcGIS Resources website is an extremely comprehensive look at this topic. However it is serious overkill for beginners.
  • Some handy ArcGIS label expressions is an article from Christopher Wesson's personal blog. Like the article cited above, it's aimed at professionals. However, the language and examples he uses are pretty easy to follow compared to most material on the subject.

Come on people! What if all I want to do is use a simple text string as a label?

  • Q: How do I create more detailed labels in ArcGIS? is an article from the Knowledge Base website hosted by MIT. It shows how string addition (also called concatenation) can be used to build a label. The introductory string "Number of floors" is added to a value stored in a land parcel database's attribute table. Notice how the Append button (or the ampersand character) is used to make this happen.

    The same article also shows a super-simple application of the Visual Basic scripting language to solve a problem that often comes up - What can I do if my label expression results in a label that is too long?