Scanning a map

The first step when converting a paper map to a digital map is to scan the map and turn it into a graphics file. You don’t need an expensive, high-end scanner to accomplish this task; most any color scanner will work. If you want to scan a large map — say, anything bigger than a legal size piece of paper — consider literally cutting it up into pieces that will fit on your scanner. (8.5 x 11 inches works well.) Instead of using a pair of scissors, use a paper cutter, such as those found at copy centers, to ensure that you end up with straight cuts. The straight cuts are important for accurately aligning the map on your scanner. Although you can scan a large map one portion at a time without cutting it, it’s more of a challenge to get the edges lined up when you stitch them together as I discuss next.
Here are some tips to improve your map scanning:

• Use medium dpi: Scanning the map between 125–200 dots per inch (dpi) is good enough; you don’t need to scan at higher resolutions typically used for reproducing photos.
• Use color photo scanning: Most scanning software has different settings for different types of documents you want to scan, such as text, line drawings, and photographs. Select the color photograph option to retain the most detail. However, remember that most maps don’t have millions of colors like photographs, so if your scanning software supports it, use a 256-color setting.
• Watch edge alignment: Place the to-be-scanned map directly on the scanner, ensuring that the edges are aligned directly against the scanner bed with no gaps. You need to keep the paper map as square as possible to reduce distortion during a scan.
• Prevent edge distortion: To help keep the map edges pressed flat, leave the scanner cover open and use a book or something heavy to set on top of the map. The edges are typically where the most distortion occurs during scanning because they tend to lift up.
• Experiment with settings: Try a couple of experimental scans first, changing the brightness and contrast settings. If you’re going to be scanning a number of maps over a period of time, write down the settings that gave you the best output so you can use them next time.
• Save the final scan as BMP: When you’re ready to produce a final scan of the map, initially save it as bitmap (BMP) format file. This produces an image that’s as close to the original map as possible; bitmap files aren’t compressed like JPG and other graphics file formats.

Bitmap files do take up a lot of memory and disk space, but after you edit a file, you can save it as another graphics format that’s smaller in size. If you have a map that’s made up of multiple image files, such as a large map cut up into a series of smaller maps, you’ll need to stitch them and a single, large image. Commercial graphics program such as Adobe Photoshop and Jasc Paint Shop Pro have commands for combining files. You can also manually stitch together images with Microsoft Paint by using the Paste From command of the Edit menu. Here’s a link to a great tutorial on stitching together scanned images: www.sibleyfineart.com/index.htm?tutorial—join-scans.htm.