One of the sweetest options of NetStumbler is the Merge function. It can turn dozens of small files into one large file. The single, large file allows operations on the entire set of data instead of operating in several small steps.

Since NetStumbler automatically creates a filename and can also save it automatically, it’s inevitable that a large number of these files will pile up. The best way to manage these is to merge the smaller files created each session into a single file. Merge only works on NetStumbler native NS1 files.

Some online NetStumbler resources allow the uploading and downloading of merged NS1 files. With these files you can work on a massive amount of data at once. Some files can contain more than 10,000 access points!

To merge an NS1 file, follow these steps:

3. Select the file to merge into the one already open.To select more than one file, hold down CTRL. There is a limit to the number of files you can select at once. This is probably due to the length of the filenames, not the size of the file.Try selecting five files or less at one time.

4. Click Open.

The NS1 file is a binary formatted file. The NS1 file is readable by few applications directly. Stumbverter is one good example. But most applications will need to import the data in some sort of text format. NetStumbler offers three export options. These formats have unique differences.

It is important to understand what may be skipped over when exporting. The three export options are Summary,Text, and Wi-scan. Each selection uses a tab-delimited output with header information.

To export a file, first open an NS1 file from the File menu. Next, select File ➪ Export ➪

There are several programs or scripts available online to manipulate NetStumbler files. Most of these are available via the forums on http://www.netstumbler.com. After registering for

The fields of export are as follows:

Latitude: GPS latitude position

Longitude: GPS longitude position

SSID: The SSID for the wireless device

Type: Type of device, Access Point, Peer, and so on

BSSID: MAC address of the device

Time (GMT): Greenwich Mean Time for the line item

SNR Sig Noise: A three-part field separated by a space: Signal-to-noise ratio, Signal level, Noise level

Name: The descriptive name for the access point if available

Flags: Specific NetStumbler items, includes WEP state, Infrastructure mode, and so on

Channel Bits: Field NetStumbler uses to record the Wi-Fi channel

Beacon Interval: The time between beacon frames for the wireless device

Export formats also include the date. Scroll down an exported file and the date will be entered on a line for each different day that data was recorded. # $DateGMT: 2003-06-03

The date and other line items are commented using the # symbol. Scripts created to work on NetStumbler exports will often filter out these comments automatically.

Summary includes only one line per device detected. This is the most common output you will use when working on the data directly. Like the Text format, summary includes every field.

The Summary format includes all of the header fields available. It chooses the entry with the highest SNR level for export. This is often the closest location to the wireless device.

Latitude and Longitude are exported in the Decimal Degrees format.

The Text format includes every data point recorded in the NS1 file. This format is useful when you want to work with the data in another program.Text format could be used to analyze signal strength for a given access point in another program like Excel. Latitude and Longitude are also exported in the Decimal Degrees format.

Wi-Scan is very much like Text format, except for the reduced number of fields included. This format does not include Flags, Channel Bits, or Beacon Interval in the output.

Wi-Scan is intended to be a universal war driving file format.Other stumbling programs may be able to import this format directly, and NetStumbler should be able to import other Wi-Scan files.

One problem you may encounter in using the Wi-Scan format is with the GPS coordinates essential for mapping. Latitude and Longitude are exported using the “Degrees Minutes.Minutes” formula, but are formatted using the Decimal notation.

For example, if the displayed format looks like this:

The format should look like this, in degrees and minutes:

When you’re working with the Wi-Scan data, it may be necessary to reformat the latitude and longitude coordinates to get accurate results from your mapping application.

With the lessons learned in Chapter 5 and the use of NetStumbler data files, you should have a nice collection of war driving data. Now you can take a look at some ways to apply that data to look at your neighborhood through the eyes of a wireless network.

There are several different ways to look at the data from NetStumbler. You could make a simple text file, plot the data on a map (as in Chapter 7), or go crazy with Microsoft Excel to create a chart based on your data.

Here are a few ways to use this data:

Determine how many wireless networks are in your neighborhood. By trolling the neighborhood, you will see how many of your neighbors are on the cutting edge.

Locate public hotspots. Discover hotspots that you can use for Internet access. It’s recommended you get permission before using any hotspot, though.

Discover if other devices are interfering with your network.Troubleshoot interference issues by scanning for wireless networks competing with yours.

Perform a site survey by tracking signal strength. Use the powerful signal strength meter to test antennas, determine range, check link status, and so much more.

Determine the range of a wireless network.Travel around the perimeter of your wireless access and see how far the signal carries. It may go farther than you think.

Perform informal market research on wireless vendors. The Vendor comun shows what products are the most popular.Will Linksys continue to rule the roost?

Gain insight into user behavior. See how many networks are not secure. See how many use the default settings. For some people, it must be a challenge just plugging in the box.

NetStumbler is a capable and comprehensive application. The features can be used in so many different ways that it will take some time to explore. Some of the features rival software costing thousands of dollars. Indeed, some functions in NetStumbler have even been integrated into these high-cost products after its popularity has grown.

It’s not only a great war driving application, but is useful for wireless network troubleshooting, informal market research, finding hotspots, and much more!

Spend some time experimenting with it and it will surely become an indispensable tool in your no-cost wireless arsenal.

Next, you can plot your war driving results in a mapping program to visualize where all of these networks are in your city. You will learn how to take data from your war driving application and convert it into a format that most mapping programs can use. Make cool maps and show them to your friends. The extent of wireless networking becomes instantly recognizable when overlayed onto a map of your city.