Calibrating the map

After you scan, edit, and save your map, one more step is left before you can start using the map with OziExplorer. At this point, your map is simply a graphics file. You can use Microsoft Paint or any another graphics program to view, edit, and print the map, but you want to turn the image into a smart map to take advantage of OziExplorer’s features.
This involves calibrating the map, which involves linking georeferenced data with the map image so that each pixel in the map has a geographic coordinate associated with it. When a map has georeferenced data, you can

• Move the cursor on the map, and OziExplorer will accurately report the coordinates of the cursor in latitude and longitude or UTM (Universal Transverse Mercator)
• Draw lines on the map to measure distance.
• Calculate the size of areas.
• Track and display your current position on the map when the computer is connected to a GPS receiver.
• _ Transfer GPS waypoints, routes, and tracks between the map and a GPS receiver.

When you calibrate a map with OziExplorer, the georeferenced data isn’t embedded directly inside the image file. OziExplorer creates a separate MAP file (.map) that contains the following information:

• The location of the map image file
• The map datum
• The map projection
• Map calibration data

Inside a MAP file, the file is in text format and can be viewed with any word processor.
Calibration requires you to identify a series of points on the map with known coordinates. Depending on the number of points that you select, as well as the map datum and projection, OziExplorer performs different mathematical calculations to link coordinate information with the map image. To demonstrate the process of calibrating a map with OziExplorer, use a scanned copy of a 1:100,000 scale USGS topographic map Some digital maps have georeferenced data embedded directly into the map image as tags or come with associated files that contain the reference data. (A common example is a DRG map.) OziExplorer can use these maps without going through the calibration process that I describe next. Check the OziExplorer Web site or the program’s online help for a full list of these supported map types.

Edit the map

After you successfully scan the map, make any last-minute changes to the image. This could include

• Adjusting the brightness and contrast to make the map more readable.

• Adding symbols or text information.
• Removing the white space (or collar as it’s known in map-speak) that surrounds the map.

Use your favorite graphics program to make any final edits to the map image. After you’re through, save the map as a TIFF, PNG, or JPG file to reduce how much disk and memory space the image takes up. (These compressed file formats are more space-efficient and memory-efficient.) The shareware version of OziExplorer can load only BMP images. Because bitmaps aren’t compressed, the entire file must be loaded into memory, which can slow down the performance of computers that don’t have much RAM.

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.

Discovering OziExplorer Features

OziExplorer is a powerful and versatile mapping program developed by Des Newman. (Newman hails from Australia, and Ozi is slang for Australia — get it?). Newman originally wrote the program for personal use during four-wheeldrive trips in the Australian outback. He released OziExplorer as shareware, which has evolved into a sophisticated mapping tool that’s constantly updated.
Some of the program’s key features are that it

• Interfaces with GPS receivers: OziExplorer can communicate with just about every GPS receiver on the market, allowing you to upload and download waypoints, routes, and tracks to and from GPS receivers and PCs.
• Works in many languages: Localized versions of OziExplorer are available in a number of different languages, including English, German, French, Spanish, and Italian.
• Provides real-time tracking: If you have a laptop connected to a GPS receiver, OziExplorer displays a moving map with your real-time, current position and other travel information.
• Is easy to use: OziExplorer boasts a large number of features, such as annotating maps and extensive import and export capabilities, all of which are easy to use.
• Supports an extensive number of map formats: OziExplorer can access many popular digital map data formats (such as DRG, a Digital Raster Graphics map) and can associate georeferenced data with common graphics file types. For example, you can take a file that you created in Paint or some other graphic program and turn it into a smart map (a map where geographic coordinates are associated with individual pixels). The best way to find out about OziExplorer’s features is to download the program and try it. (OziExplorer works with PCs capable of running Windows 95 through XP.).

• Trial: The trial version is a limited version of OziExplorer that has all the program features enabled, except the program can’t

• Communicate with GPS receivers
• Save or load waypoints, routes, or tracks
• Save maps as image files
• Run for more than an hour at a time

• Shareware: The shareware version has a number of features disabled and has the following limitations:

• Only bitmap (BMP) images can be imported as maps (as opposed to many graphics file types in the registered version).
• Only two points can be used to calibrate a map, reducing the potential accuracy. (Up to nine points are available in the registered version.)
• Limited support is available for map projections, grid systems, and datums (compared with extensive support in the full version). Between these two programs available in the install package, you’ll be able to get a feel for all OziExplorer’s capabilities. And when you register the shareware version, the full monty of features is enabled. The $85 registration fee is a nominal investment considering the many features that the full version of OziExplorer offers.
If you’re looking for a street and road navigation program, OziExplorer isn’t the best choice. Ozi is more suited for adventures off the beaten path. If you need a program that helps you find the best route between two addresses on streets and highways, you’re much better off using some of the commercial mapping programs .
For more practical information on OziExplorer, including troubleshooting tips, check out the popular Yahoo! Groups e-mail list and forum devoted to the program at groups.yahoo.com/group/OziUsers-L.
In addition to OziExplorer, Des Newman also has two other related mapping programs:

• OziExplorer3D: This program is used in conjunction with OziExplorer to display maps in three dimensions. OziExplorer writes elevation data to a file, which OziExplorer3D uses to display a 3-D representation of the map. OziExplorer3D is priced at $30.
• OziExplorerCE: OziExplorerCE is moving-map software for Pocket PC (formerly known as Windows CE) PDAs. You create maps and plan trips with OziExplorer on your PC and then download the map data to your PDA to use with OziExplorerCE. When you connect your PDA to a GPS receiver, the program retrieves GPS data and displays your current location on a map. The PDA version of Ozi costs $30.

To discover more about the features of these two programs and download demonstration versions, go to www.oziexplorer.com.

QuakeMap

QuakeMap is written by Sergei Grichine and was originally designed to download worldwide earthquake data from various Internet sources and display the information on maps. The program has since evolved into a general purpose, mapping utility that uses TerraServer-USA data. You can use GPS data with QuakeMap, and if you’re a geocacher, the program has several specialized features designed for the sport.