The Global Positioning System, known as GPS, is made up of a number of satellites in orbit around the Earth. These satellites (24 active, with a few spares) maintain a precise position relative to Earth. GPS receivers continuously receive updates of the position of all 24 satellites in orbit. By computing the distance from the receiver to each visible GPS satellite, your GPS receiver triangulates its position on Earth in the form of Latitude, Longitude, and Altitude.

Consumer-grade GPS receivers are not completely accurate. High accuracy is more costly, but most consumer GPS receivers using the new Wide Area Augmentation System (WAAS) or Differential GPS (DGPS) capability can give you a position accuracy of less than 3 to 5 meters. In the case of mapping results, often the maps you are working from are not entirely precise, either. Mapping accuracy is always a game of ever-increasing accuracy and the cost of obtaining that accuracy. For our purposes, though, a $100 GPS and $40 mapping software works perfectly.

GPS works on the very basic principle of triangulation. Each satellite beams down a signal to Earth. It also beams down the time the signal was sent, and of course, which satellite the signal came from. GPS is also about the most accurate time source available to consumers. Each satellite carries an atomic clock, and keeps your handheld unit timed to that clock. By knowing the exact time (to the nanosecond) that the signal left the satellite, the time when the signal reached the receiver, and knowing the speed of light, distance is computed. (See Figure 7-5.)

When at least three distances are known (from three GPS satellites) the receiver’s position on Earth is known and recorded as latitude and longitude. If a fourth satellite is visible, altitude will also be computed.

Altitude is pretty standard, measured in meters or feet. Latitude and longitude is another matter. In its basic form, latitude and longitude is recorded as degrees, minutes, and seconds, north or south of the Earth’s equator and east or west of the Prime Meridian (the line that separates the Western and Eastern hemispheres).

The procedure for mapping is a basic step-by-step process:

I’ll cover each of these steps in the following sections.

To gather the data, someone needs to go war driving. See Chapter 5 for more on war driving. If you don’t have your own results, others may have posted their files.Try performing a Google search for Netstumbler NS1. The minimum amount of data needed to make a map is the latitude and longitude of a single wireless access point. More information will make the map more interesting, but is not necessary.

NetStumbler has become the de facto standard when it comes to working with war driving data. Most war driving programs have a converter available to export into NetStumbler Summary Export format, also called “wi-scan summary with extensions.” NetStumbler supports this format directly from the File menu. Click File ➪ Export ➪

Summary. Then enter a file name using the .txt extension to ensure that Notepad or another text editor will be able to open the file directly. In this example, use summary.txt. For more about exporting file formats from NetStumbler, see Chapter 6.

The conversion process is the most difficult part of war drive mapping. There are so many different mapping programs and, of course, they don’t all speak the same language. This is where Microsoft MapPoint and StumbVerter make things simple. One program, StumbVerter, imports the Summary.txt file and plots the APs on a map. See Figure 7-6 for StumbVerter in action.

If you don’t have the $300 MapPoint program, try searching at Netstumbler.com for a conversion tool for your mapping program. In the meantime, we’ll do a conversion using one of the best data manipulation programs available, Microsoft Excel.

The NetStumbler Summary format is a tab-delimited ASCII file.To read this file into Microsoft Excel, click File ➪ Open. In the the Files of Type drop-down list, select the All Files option. This will show text files and more in the Open dialog. Select the Summary.txt

When Excel opens this type of file, it immediately starts the Text Import Wizard, as shown in Figure 7-7. Choose the Delimited option and click Next. Make sure that Tab is the delimiter type. Click Next again, then click Finish. There is no need to specify data formats for each column. Once your data is in Excel, it’s just a matter of deleting fields that aren’t needed, and formatting the data to work with your mapping software. See Figure 7-8 for an example of a stripped down spreadsheet.

Mapping programs, in general, have an import function. This is helpful to add the addresses of points of interest, and of course, access point locations. A few different programs will be covered here. Also, the manual import from Microsoft Excel will be performed using Microsoft MapPoint. (Surprise: They work really well together!)

In Microsoft MapPoint, the import comes in the form of a “pushpin.” Extra detail on the location is stored in a text “balloon.” Figure 7-9 shows an example of the standard pushpin and a

text balloon showing details about a plotted wireless network. This concept of pushpins and balloons is followed by other applications, too. MapPoint has some pretty sophisticated data visualization abilities.To get simple pushpins onto a map requires navigating through the maze of wizards and checkboxes. Other programs have simple import procedures (see below) but they don’t have the massive ability to show data in so many ways. See the section “Visualizing Extras” later in this chapter for an example.

Here are the steps to bring in a formatted text or Excel file:

If you do not want the contents of a column to be displayed in the text balloon, select “Skip Column.” To have the data show up, assign it the value of Name, Name 2, or Other Data.

The Data Mapping Wizard has many features and accesses some interesting stuff. Later in this chapter we will use it to plot signal strength using the Shaded Circle feature. It has nine differ-

 

ent ways to display data: shaded area, shaded circle, multiple symbol, pie chart, sized pie chart, column chart, series column chart, and everyone’s favorite, the pushpin. Also, with MapPoint’s built-in demographic data, you can spend hours viewing the strange habits of your neighbors, such as “Adults who use sore throat products” as viewed by state, Zip code, or census tract.

Sometimes while war driving, the GPS will conk out, get disconnected, and so on. If that happens, you may record an AP with the latitude and longitude of N 0.0 by E 0.0. MapPoint will happily plot that and expand the map to show those APs off the coast of Africa at 0 degrees latitude by 0 degrees longitude.When plotting these sources, you can delete them, or ignore them. If you war drive the same access point at a later time, the coordinates will be updated.

See Figure 7-10 for a map created by MapPoint using a text file import.

Microsoft MapPoint Using StumbVerter

StumbVerter is a free program that converts files from NetStumbler format into Microsoft MapPoint format (see Figure 7-11). The unique feature of StumbVerter is that it uses Microsoft’s common object model (COM) programming interface to work directly with the MapPoint map data. The practical upshot is that you do not need to import into MapPoint. StumbVerter does it all automatically.

Follow these steps to begin working with StumbVerter:

1. Download StumbVerter from www.sonar-security.com and install it onto your system. (Note that you need MapPoint installed before you can use StumbVerter.)

2. Run StumbVerter and select the down arrow next to the Map button to choose “Create New North America.”

3. Now click the down arrow next to the Import button to select NetStumbler Summary.

4. Open the file previously exported from NetStumbler. Progress is shown during loading and drawing the map. Be patient if there is a lot of data.

The final step in importing results is showing it off! Each program has a different format for presenting data, but it’s all easily understood. Sharing your maps with others makes for some great conversations. As you can see from the maps we created in this section, much of our war driving took place on freeways around Los Angeles. In some areas, APs are so dense it’s almost like leaving a trail of breadcrumbs showing your path of travel.