Last week I was working with a map layer of water mains and at 1:2,400 scale the shorter mains were labeled with leader lines (because they were too short to show the entire label along the line). My map was initially using the Transverse Mercator based on NAD_83 coordinate system. Then I learned that I needed to make the map in a different coordinate system as well: WGS_84, so I could serve it and have it mash up on our ArcGIS Online Street Map.

The key issue for me turned out to be the linear units for each of these coordinate systems; WGS_84 is decimal degrees, while the Transverse Mercator is meters. This was an issue because my Maplex labeling rules for offsets were originally set using meters.  In particular my leader line rules used an offset of 25 meters--well when that gets arbitrarily switched to decimal degrees, 25 suddenly means a great deal more in terms of distance (about 1,500 miles). It also meant more processing time for my CPU--which finished the labeling job in a bit over seven minutes (instead of less than two seconds). 

So, a best practice for anyone making a map that uses Maplex and may have to change coordinate systems is to definitely use page units for offsets and other parameters that give you the option to choose between map units or page units. Here are the Maplex parameters to check:

Point Layers:

  • Offset
  • Remove Duplicates

Line Layers:

  • Offset
  • Repeat label
  • Overrun feature
  • Remove duplicates

Polygon Layers:

  • Overrun feature 
  • Remove duplicates