By Peter Kasianchuk, Mapping Center Cartographer
A number of maps, particularly those geared towards outdoor tourism, rely on a convention that uses standard icons to list the services or amenities that are available at some place on the map. Using cartographic representations simplifies what used to be a rather unwieldy task from the perspectives of data modeling, data management, and symbology.
The workflow is pretty straightforward, and really only depends on how your point data for the locations of services or amenities is modeled. In the case of the Crater Lake data, each point feature stores a text string which defines the list of amenities and services available at that location. As text, this was not useful to automate the assignment of the symbology. In the original map we used a very complex labeling expression to create the effect of the marker lists. By using cartographic representations we were able to avoid all of that, and found that it was actually faster to do the manual work of assigning the symbols in the representation rule management environment. Here is how we did it:
- First we created unique values symbology for our points, based on the name, with the standard layer symbol properties. This worked because we needed to create a representation rule for each site. This would allow us to assign the amenity and service symbols on a site by site basis.
- Next we converted the standard symbology to representations.
- Then we changed how each rule worked in one of two ways:
- If there was only one amenity or service at a point feature, we applied the marker symbol that matched what was at the site. This was accomplished when we converted the symbols to representations.
- If there was more than one amenity or service at a point feature, we added additional marker layers. This required a bit more work.
- We applied the appropriate offsets to each representation symbol marker layer. As shown in the figure above, the marker size is 12 point, so the offset in the X axis is 14 points to account for the marker symbol plus some separation between it and adjacent markers. In this case, the markers are drawn to the left of the point feature, so the X axis offset is defined as a negative value.
Now the appropriate set of representation marker symbols are associated and stored with each point feature (which is in its original geographic position). Since the data now stores the symbology (rather than the specific map document or layer file), it can be shared along with your cartography.
Beyond being much easier to accomplish, another advantage to using cartographic representations is that your data and maps are easier to share. In the past, such a map would have been created using character marker symbols based on glyphs from fonts. That meant having to remember to embed the fonts in your output files, or share the fonts when you shared the map document. For example, a custom font (an early version of one that will be released with ArcGIS 9.3) was used for the Crater Lake map. The screen shot below shows what the map looks like when the fonts for the marker symbols are not managed:
Have you seen anything like this before? Notice %s, ½s, and other symbols have been substituted where park amenities and services symbols should be shown. Representation marker symbols do not depend on fonts, so by using them instead of character marker symbols these problems with sharing maps are removed.
All of the marker symbols shown here are available in a style file
created from the Esri Forestry 1 font and converted to representation