Welcome to my little spare time project. I've been working on this on and off for about a year as time and motivation allows.
This is more of an excuse to have some fun with Maps and Geocoding than anything else but it hopefully provides something interesting to play with. "Geocoding" means to convert physical addresses into longitude and latitude coordinates. Behind the scenes, this site has been slowly geocoding all active amateur radio addresses in the FCC license data. The FCC data includes all licenses which have a status of "active".
I've found it an interesting project with lots of little challenges. Some of this is because of the wide variation of population and therefore "ham density" throughout the country. I've had to balance that with performance issues both at the database query level and practical limitations of Google Maps. The data is also kind of messy with multiple licensees at one address and multiple addresses at the same location. This last issue is mostly due to spelling variations. In general, one marker appears on the map for each unique latitude / longitude point.
The performance / data quantity compromise I've come up with is that it searches within a 20 mile radius of the map center and has a limit of 200 location markers. The results are sorted by distance which means that the circle is complete until it hits the 200 markers. I haven't found a gridsquare that has more than 200 so if you center on a gridsquare, I think we always get all in that square.
The geocoding has been done over a long period using a combination of Geocodio and Nominatim / OpenStreetMap. When there are no new addresses to geocode, it retries addresses that have previously failed. These sometimes succeed because of improved geocoding data.
A weekly import from the FCC usually happens late on Sunday, eastern time. Only those stations with a status of "active" are retained. About 1000 addresses are added and deleted each week. Geocoding the new addresses is usually complete by early Monday
Of course some addresses are PO Boxes and other mailing services. Addresses starting with "PO Box" are simply excluded. Also, many licensees are not active in the hobby. Be that as it may, it can be fun to play with the Street View feature of the maps to look for antennas.
Although I've only considered data from the USA, it's written in a generalized way so it can handle data from other countries but I'm not aware of any other countries who make their data publicly available.
Anyway… I think it's pretty much "done" in terms of new features unless someone comes up with a good idea. I've probably spent way too much spare time on this already and it's time to get my antenna up again and do some QRP construction. Feedback is welcome. The easiest way is by email to tetranz (at) gmail.com