OziExplorer and World War I

The 1980s movie Gallipoli recounted the Australian experience of fighting the Turks during World War I. Although long before the time of computers and mapping software, WWI also has a link to OziExplorer.
Howard Anderson wrote a fascinating article on using OziExplorer to locate old World War I trench lines in France and Belgium. The remains of the trenches are long gone, but by using old maps from the period, scanning them, and adding georeferenced data, Anderson was able to clearly determine where the trenches were dug during the early 1900s.
After he had scanned and georeferenced the old military maps, Anderson used OziExplorer to draw GPS tracks on personally created digital maps to trace the outlines of the trenches. He also used waypoints to identify military and land features. Anderson then took the tracks and waypoints and overlaid them on a modern map in OziExplorer. This revealed where the longago war emplacements once stood. Anderson’s last step was to visit France with a GPS receiver and his old and modern maps. He found that, with relative accuracy, he could stand on the site of a trench where his grandfather had fought over 85 years ago.

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.

Moving from Paper to Digital Maps

OziExplorer supports a number of different digital map types that use georeferenced data (information that allows a program to precisely identify locations and coordinates on a map). But one of the program’s most powerful features is its ability to turn your own graphics files into georeferenced maps. This means if you have a paper map, you can scan it, load it into OziExplorer, and effectively make it an electronic (digital) map. This is a three-step process:

1. Scan the map. Use a scanner to create a digital image of the paper map. Stitch individual map pieces, if necessary.
2. Edit the map. Make changes to the scanned map before it’s used.
3. Calibrate the map. Load the edited map into OziExplorer and associate georeferenced data with the map image.

The following sections explore the above three steps in further detail. Scanning and calibrating your own maps can be fairly time consuming and sometimes frustrating if you can’t seem to get the map coordinates to match up with reality. Some maps are definitely easier to calibrate than others. If you’re not technically inclined or are somewhat impatient, you’ll probably want to stick to importing maps that are already georeferenced, such as freely available United States Geological Survey (USGS) DRG topographic maps.