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 Previous: ARRL In Action: What Have We Been Up To Lately? | ![Next (later) Story](/images/sty-up.gif "Field Day 2003: "Gustnado" Blows Away Florida Site; Van Called to Duty in Kansas"){kind=small} Next: Field Day 2003: "Gustnado" Blows Away Florida Site; Van Called to Duty in Kansas |
By Kenneth Harker, WM5R
July 1, 2003
More than simple drawings of where club members live, clubs can use maps to help plan activities, assist new members in finding Elmers, coordinate during disasters and more.
For a few years now, I have been the Webmaster for the Central Texas DX & Contest Club. One of the features on our Web site is a set of maps showing the locations around town and in the surrounding countryside where our members live. Our maps also highlight to show where the local DX Cluster nodes are located. The maps are useful for coordinating club activities and for connecting club members with new and prospective club members who live nearby.
In our particular club, highlighting the DX Cluster locations can help members decide which clusters to try out. In a repeater club, highlighting repeater locations might be a desirable focus of a club map. An ARES organization might highlight member locations, EOCs, hospitals, Red Cross headquarters and other points of interest. Maps can do a lot that is useful for radio clubs.
 The red dots show the locations of CTDXCC members in the Austin, Texas, metropolitan area. Green dots represent the locations of area DX Clusters. |
Making a map of your club members' locations is easier than you think, and if your club is located in the United States, it can be done without purchasing any software. The maps I've made for the Central Texas DX & Contest Club were generated using the US Census Bureau TIGER Map Server. The TIGER Map Server (TMS) can be browsed interactively, or with a simple data file you can create in any text editor, you can draw custom maps on-line.
The map server can add several data layers to your map, showing city labels, county labels, highways, parks, railroads, census tracts, bodies of water and more. The city/county/road labels are all from 1990 data, so some of them may be out of date. The TIGER map server was developed in 1995 as a proof-of-concept project that proved to be useful enough to leave up and running after the end of the experiment. It's a fine tool for building a simple map of radio club members' locations. Most importantly, the maps you download from the TIGER map server site are in the public domain and you are free to use them as you choose. More details about what the TMS can and cannot do and what you can use it for are on the Web.
To generate a map using TMS that has multiple markers displayed on it, you will need to prepare an ASCII text data file. The data file contains one line of text for each marker, indicating the exact latitude and longitude for the marker, the icon to use for the marker, and a label (if any) to put next to the marker. This data file is accessed by the TMS over the Web, so you will need to place it--temporarily, at least--on a Web server so you can pass the URL to the TIGER Map Server. A map can be requested directly from TMS by using a URL of the following format:
http://tiger.census.gov/cgi-bin/mapgen?parameter¶meter&...
 This map contains the same set-up information as the previous map, but increases the scale to show hams farther out from Austin. |
By providing the right parameters, you can turn the various data layers (the cities, counties, railroads and more) on or off. You will use the "murl" parameter to pass the URL of your marker data file. This is documented thoroughly on the Web. An example of a file that places two markers on the map looks like:
#tms-marker
-97.765723,30.423949:reddot10:WM5R
-97.731050,30.286850:reddot10:N5XU
The first marker will be placed at 97.765723 degrees West and 30.423949 degrees North, it will be a red dot 10 pixels in diameter, and the text label for it is "WM5R." The coordinates are given as longitude,latitude (note the order) with positive numbers for north and east, negative numbers for south and west. "reddot10" is one of 77 different marker icon choices available. You can use red dots, green dots, blue dots, stars and pins, to name some of the many choices with which you can experiment.
To generate a map with a file, you will need to load a URL in your Web browser that looks like the following example:
tiger.census.gov/cgi-bin/mapgen/.gif?lat=30.435&lon=-97.79&off=CITIES
&wid=.66&ht=.66&iht=900&iwd=900&murl=http://www.example.org/example.dat
What does all this mean? ".gif?" means that the result will be a .gif formatted graphics file, and will use the following parameters, each of which is separated by and ampersand (the & symbol). The first two parameters are "lat=30.435" and "lon=-97.79". These define the center of the map in latitude and longitude, using decimal degrees, with positive denoting north and east, negative south and west. The next parameter is "off=CITIES". This overrides the default, which is to draw city and town labels on the map. "wid=.66" and "ht=.66" specify how many degrees wide (in longitude) and high (in latitude) the map will cover. In this case, we're drawing a square map that covers 2/3 of a degree by 2/3 of a degree, a good size for many metropolitan areas. "iht=900" and "iwd=900" specify how many pixels high and wide the map should be. Finally, "murl=http://www.example.org/example.dat" specifies the URL of the marker data file. (The data file can be removed after the map is generated.) You will want to experiment with different map centers, widths and heights to generate the right map for you.
 A wide view of DX Clusters in the Austin area. |
Once you generate a nice map that you like, save a copy to disk and use that for your club Web pages, meeting handouts and hamfest displays. If you place the URL you used to create the map into your Web page design, you will force the TIGER Map Server to re-generate the map every time someone visits your Web page. This can be slow and is unnecessary. You would also need to keep the data file online all the time, which you might not want to do. Save a copy of the map, put that copy on your Web server and use it instead.
The biggest challenge to drawing really nice maps of radio club members' locations is determining accurate latitude and longitude values for each club member. You probably have a street address for each club member, but how do you convert that to latitude and longitude? The process is called "geocoding." More information on geocoding options is on the Web.
An easy source of latitude and longitude values are the coordinates reported in some of the online call book servers, such as QRZ.com and Buckmaster HamCall. These servers use geocoding approximations based upon the center of ZIP code boundaries, six digit Maidenhead grid locators, and other techniques that make the results close, but sometimes less than perfect.
Depending on the scale of your map, these latitude and longitude values may be good enough. If you want to get really accurate, though, you'll want to explore other options. See the ARRL Web site for general information on the Maidenhead Locator System.
One option, of course, is to use the Global Positioning System (GPS). Handheld GPS receivers are so common now that simply asking your club members for their latitude and longitude to five or six decimal digits of precision will get a lot of answers. For those that remain, an afternoon of driving around town with a GPS receiver to get the rest may be all you need to do.
Another option is to use TopoZone. The maps served at the TopoZone Web site are scanned images of USGS topographic maps. There is no search facility for finding a location based on street address and most of the streets on the USGS maps are not labeled, but if you can navigate to the right spot on the map (using another online mapping engine as a guide, perhaps) and click on it, TopoZone will tell you the latitude and longitude to four decimal degrees of precision. Unfortunately, many USGS topographical maps are years out of date, so streets may not match the current reality!
Finally, online geocoding services are available. Tele Atlas offers one such service. You can test drive their geocoding service for free (US addresses only) up to 25 queries. A license to geocode 1000 addresses is just $50. Using a professional geocoding service like Tele Atlas will give you really accurate results. Many Geographic Information System (GIS) software packages can also do geocoding, as well as excellent maps. For those serious about making maps, an investment in GIS software may be a good decision.
Maps can say so much more about your radio club membership than a simple list of club member names with counties or grid locators. Clubs can use maps to help plan their services and activities, to assist new members in finding Elmers, to coordinate during disasters and more. With the US Census Bureau's TIGER Map Server, it has never been easier to generate a nice digital image map with markers showing the locations of ham stations.
A ham since 1993, Ken Harker, WM5R, is a computer
scientist for an Austin, Texas company that specializes in Internet performance
monitoring and analysis. He holds an Extra class license. He is a former
president of the University of Texas Amateur Radio Club and is the current
Webmaster for the Central Texas DX & Contest Club. You can contact the
author by surface mail at 7009 Fireoak Dr, Austin, TX 78759, on the Web, or via e-mail at wm5r@arrl.net.
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