Visualizing Extras

The beginner war driver will plot data onto a map and call it a day (or night). You can go a few steps further with these extras and really get noticed. The following sections cover a few interesting visualization techniques that the professionals use.

3-D Rendering

Some mapping applications have 3-D visualization extras. DeLorme TopoUSA and XMap have this feature built-in. Figure 7-15 shows a 3-D topographic map overlayed with satellite

imagery and war driving access points plotted onto the image. There’s a lot of visual information in this type of picture.

Custom Symbols

Most mapping program that import pushpins (whether they are called pushpins, symbols, icons, or something else) have some method of changing, or creating your own graphic for the pushpin. You can really spice up a map plot by using, say, a recognized logo for the Wi-Fi hotspot. For example, the map in Figure 7-16 was created using the SOCAL WUG logo and shows several real and hypothetical SOCAL WUG hotspots in the Los Angeles area.

Filter your war driving results before importing the NetStumbler summary file into the mapping program. Microsoft Excel (again) is great for sorting entries to make it easy to delete sites you don’t want to map.

Your specific software should have information available on creating your own symbols. But in case it doesn’t, a little digging on Google Groups will find others that have the same question.

Microsoft has made their MapPoint icons available as Windows .BMP (bitmap) files. Search Microsoft for “mappoint” to find the file in the download center. Use these files as a starting point to make changes.

DeLorme provides downloadable .DIM files (DeLorme Image Files) that can be installed in the Symbols directory to add hundreds of icons.

This list explains how to make a custom logo in Microsoft MapPoint:

1. Open a new MapPoint map without any pushpins.

2. Select View ➪Toolbars and make sure that the Draw toolbar is active.

3. Click the tiny upside-down triangle next to the pushpin icon on the Draw toolbar.

4. Click the button marked Import Custom Symbol.

5. Select a supported image file to import (currently Icons, BMPs, and Cursor files) and click Open.

That’s it! Now you have a custom symbol that can be placed manually using the symbol button. Or you can select the symbol while importing latitude longitude data. Make sure the file you select is smaller than 128  128 pixels, and note that the color white will be made transparent. 128 pixels square is pretty big on-screen. You probably want something in the 40 to 80 pixel range to really stand out.

Satellite and Aerial Imaging

One of the more interesting mapping imagery trends in recent years is the high availability of satellite and aerial photography. Satellite images cover vast swaths of the globe. Commercial vendors have satellites in orbit with their only job being to take pictures and make them available for purchase by the commercial sector. Spy satellites for the masses!

Aerial photography is similar to satellite, but usually at a much higher resolution (you can see the color of cars in the driveway and find out who has a pool in your neighborhood). A specially equipped airplane will fly a pattern over an area while taking photographs. These photos are stitched together to create a highly accurate aerial view. DeLorme products allow you to purchase and download overlays for your basic data sets. 10-meterresolution

satellite overlays (SAT-10) are available for every state for a reasonable cost (about a hundred dollars). If you don’t need this type of aerial view, the built-in data works great, too. There are also vast resources on the Web for creating aerial and satellite image files to play around with. Much of this data is freely available from sources like the U.S. Geological Survey, a government operation that makes much of the data free for download in small quantities. Your tax dollars at work!

Some sites to try out with satellite and aerial images:

Space Imaging—Gallery of IKONOS and other satellite images:

www.spaceimaging.com.

USA PhotoMaps—Free aerial photo viewing software: http://jdmcox.com.

U.S. Geological Survey—Downloads and links to images: http//www.USGS.gov.

Microsoft’s original Terraserver—View images online:

http://terraserver-usa.com.

GlobeXplorer—Incredibly accurate satellite and color aerial photography online:

www.globexplorer.com.

Some sites incorporate aerial and satellite images seamlessly. So when you are zoomed out the

view is from a satellite photo. Zoom in and the system automatically switches to aerial photos.

Neat!

Signal Strength Mapping with MapPoint and Excel

This is the last time the chapter will mention Excel (well, maybe in the Summary). In this section, we will use Excel to ferret out all of the signal information from a single access point. By plotting these signals with the MapPoint “Shaded Circles” feature, the signal area can be easily plotted. Figure 7-17 shows the final results from tracking a single AP. The dark spots show the stronger signals, and that’s very likely where the AP is located.

When you are war driving, choose the type of antenna that’s appropriate for the task. To locate an access point after the fact, as we’re doing here, an omnidirectional antenna works best to evenly capture the Wi-Fi signal. A directional antenna would be used to see how far a signal reaches, but it would be harder to locate an AP. This stems from the signal information being


recorded along with the latitude and longitude of where the antenna is located, and not where it is pointing.

These are the steps to build a signal strength plot using NetStumbler, Excel, and MapPoint:

1. In NetStumbler, turn off the automatic save feature under Options.

2. Choose an access point to plot (it works best one at a time) and delete every other AP in the list. (Again, disable the “Save Automatically” feature before deleting, or you may erase data permanently.)

3. Export the NetStumbler file in Text format. This format saves every data point for every AP in the list.

4. Open the exported text file in Microsoft Excel.

5. Follow the prompts on the Import Text Wizard to choose a tab-delimited file.

6. Perform a Data ➪ Sort to remove fields that begin with the “#” symbol. These are comments and can be removed. Keep the one commented row with the field headers.

7. Delete extra columns that you will not be using so you are left with the Latitude, Longitude, and the “[SNR Sig Noise]” column.

8. Now you get to use the “Text to Columns” feature in Excel to split that [SNR Sig Noise] column into usable numbers. Select the column with the [SNR Sig Noise] header (probably column C).

9. From the menu choose Data ➪Text to Columns. This opens a wizard.

10. In the Convert Text to Columns Wizard, choose “Delimited” in Step 1. Choose “Space” as the delimiter in step 2. You will see the numbers split up in the data preview window.

Click Next, and then click Finish to close the wizard. The signal data should now be split into five columns “[“, “SNR,” “Sig,” “Noise,” and “].”

11. Now it’s time to choose which signal data is going to be plotted. SNR (signal-to-noise ratio) is the most usable, but may not help you locate the AP. Sig (signal strength) does not always equate to a usable signal, but makes finding an AP easier. Delete the columns that will not be plotted. (Our example will use the Sig field, so brackets, SNR, and Noise will be deleted.)

12. Convert the Latitude and Longitude data into the / format required by MapPoint using the Find and Replace feature in Excel.

13. Now select Save As to save the file as an Excel Workbook (.XLS).

14. Open Microsoft MapPoint.

15. Choose Data ➪ Import Data Wizard from the menu and choose the Excel file you just saved.

16. Make sure the “First row contains column headings” check box is selected. Click Finish if the data matches up (Latitude under Latitude, and so on).

17. Next comes the “Data Mapping Wizard - Map Type” dialog box. Usually you select pushpin to mark where an AP is located. This time select “Shaded Circle,” and click Next.

18. The data field to map should read “Sig.” Click Next.

19. Now comes the fun part. Adjust the data range numbers (see Figure 7-18) to choose a range that will give some meaning to the map. Something like 100 at the top and 50 at the bottom works well for plotting signal strength.

20. Click Finish.

Now you have a great representation of signal strength on an easy-to-use map. Use this for site surveys, finding how far your hotspot reaches, searching for elusive access points, and impressing your friends!

Summary

Data visualization can come in many forms. The great thing about war driving is that you, yourself, can gather data quite easily. And mapping it is just one way to visualize what’s truly going on in the ether. Did you ever think so many people had wireless networks? It’s amazing to see them pop up on your screen when nothing is visible to the naked eye.

This truly is a way to see the invisible and get a glimpse of the popularity of wireless networking. You are performing your own research with the data being gathered and visualized. In the next chapter, we will switch gears a little and start working directly with access points. You have plotted the location and signal strength of APs in your neighborhood. Now how about finding a way to bring Wi-Fi to poor coverage areas? Read on to Chapter 8 to build your own weather-resistant, outdoor access point.