GIS Tips – ArcGIS Scalebar Prints incorrect Scale

Problem: Your scale text says 1 inch = XXX feet, but when you print out your map, 1 inch = something else.

It is rare you will be caught making such a mistake, because maps have to be set up in a particular way for it to be noticeable. But if it happens, it is quite disconcerting. I worked in an office full of engineers who asked me to create all maps with a scale of 1:a multiple of 12, so that 1 inch would be equal to a round number of feet. This way, they could take their engineer’s rule to the map and figure out exactly how long things were. At one point, one of them took that ruler to the scale bar, and saw something like this.

A ratio of 1:24,000 means that 1 inch should equal 2000 feet, just as the scale text says. However, the 2000 foot portion of the scale bar is not 1 inch long. Therefore, this map could not be used to make the measurements engineers like to make. If you are creating paper maps and you report the scale in any way other than just a scale bar, it is critical to avoid such distortion.

When I went to diagnose the problem, I found three places where this distortion can happen.

    1. When printing directly from the ArcMap Layout view.
      • Map will be distorted if you Scale Map to Printed Paper
      • Instead, you should Tile Map to Printer Paper

    1. When exporting to a PDF file
      • Map will be distorted if you Clip Output to Graphics Extent
      • Instead, you should make sure that box is unchecked

Related note: If you start getting complaints that point symbols are showing up weirdly (for example, as exclamation points) in your PDFs, check Convert Marker Symbols to Polygons. Embedding document fonts should take care of this, but it doesn’t always work.

  1. When printing from a PDF file

Even if you correctly exported the PDF to scale,

  • Printout will be distorted if you Fit or Shrink to Printable Area
  • Instead, you should select Page Scaling: None

In all three cases, the correct option should be selected by default, but you need to double check. When printing anything other than a map, it makes sense to have the computer shrink or enlarge it just slightly so it fits to the page with nice even borders on all sides. It looks better that way. But it is deadly to maps! Any scale text on those maps will no longer reflect reality. Scale bars, however, are safe because they will change size along with the rest of the map, remaining correct. For this reason, I don’t recommend using scale text on maps that are exported to GIFs or JPGs and meant only to be seen on a screen. Their size will be changing all the time with differing monitor resolutions and zooms, so the only thing you can depend on is that scale bar.

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