What is the radius for?
The radius of a location is roughly the distance from the center of a geographical area to the outer edge of the specified area. A small city, for instance, has a much smaller radius than a large city, and a large city will likely have a much smaller size than a state or province. While it's not generally important that this number be exactly right, it is important to make sure it's approximately correct since it's used to help accurately display search results. A location 'somewhere in California' is vague, while a location such as 'Lincoln Park, Seattle, WA" is very specific, and Atlas Quest needs to know how vague (or precise) these are to accurately display and sort letterboxes and events.
If you are using a specific address, the radius can be very small--0.01 miles, for instance. If your location is a park, take a look at the size of it on a map. From one side of the park to the other, how far is it as the crow flies? Take that distance, divide it by two, and that's the radius for your park. Small parks might have a radius of 0.01 miles, but large parks can be several miles. A park such as Yosemite National Park might be 30 miles or more in size!
Cities and towns are usually at least one mile wide, but the largest cities can often have a radius exceeding 30 miles. Remember too, we're referring to the geographical size of a city, not the population. New York City has a radius of about 20 miles, but Anchorage, Alaska, has a radius that's over 30 miles. While the population of New York City is considerably larger than Anchorage, the geographical footprint of New York City is considerably smaller.
Counties, states, and countries can have even an even larger radius. For California, the geocoder assigns a radius of 412 miles. For the entire United States, the radius expands to 3,881 miles.
AQ will do some basic "sanity checks" on any radius you enter. For instance, AQ will not allow you to use a radius for a city that's larger than the radius of the county that it's located in. And a city that's 300 miles wide would certainly seem a little suspicious, even if it is in a county that's more than 300 miles wide, but it's really up to to you to make sure the radius is accurate.
If you aren't sure what the radius of a location is but you know the area of the location—Wikipedia often includes information about the area of a park or other location—AQ will also accept that and convert it into a radius for you. To list an area in square miles, type "m2" after the area. To list an area in square kilometers, use "km2" after the area. Example: Wikipedia shows that Seattle, WA, has an area of 369.2 km2 (or 142.5 sq mi). Instead of typing in a radius, which is not provided on Wikipedia, you could type "369.2 km2" or "142.5 m2" as the radius. It's important to include the "m2" or "km2" after the number so AQ knows that you aren't typing a radius! AQ will convert this to 8.08 miles radius. The actual radius, as returned by one geocoder, is 11.4 miles, so the area generates a result that's slighter smaller, but the important thing is to be approximately correct than precisely wrong! While 8.08 miles might be a little small, it's close enough for our purposes and is better than not providing an actual value at all.
Another thing that the radius is used for—when displaying maps showing your location, it determines how far to zoom in or out on the map. A location with a radius close to 0 will be zoomed in to the maximum extent possible, while a large radius of dozens of miles might zoom the map out to show the entire state, or an even larger radius of several hundred miles might show most of the entire country.
If you are using a specific address, the radius can be very small--0.01 miles, for instance. If your location is a park, take a look at the size of it on a map. From one side of the park to the other, how far is it as the crow flies? Take that distance, divide it by two, and that's the radius for your park. Small parks might have a radius of 0.01 miles, but large parks can be several miles. A park such as Yosemite National Park might be 30 miles or more in size!
Cities and towns are usually at least one mile wide, but the largest cities can often have a radius exceeding 30 miles. Remember too, we're referring to the geographical size of a city, not the population. New York City has a radius of about 20 miles, but Anchorage, Alaska, has a radius that's over 30 miles. While the population of New York City is considerably larger than Anchorage, the geographical footprint of New York City is considerably smaller.
Counties, states, and countries can have even an even larger radius. For California, the geocoder assigns a radius of 412 miles. For the entire United States, the radius expands to 3,881 miles.
AQ will do some basic "sanity checks" on any radius you enter. For instance, AQ will not allow you to use a radius for a city that's larger than the radius of the county that it's located in. And a city that's 300 miles wide would certainly seem a little suspicious, even if it is in a county that's more than 300 miles wide, but it's really up to to you to make sure the radius is accurate.
If you aren't sure what the radius of a location is but you know the area of the location—Wikipedia often includes information about the area of a park or other location—AQ will also accept that and convert it into a radius for you. To list an area in square miles, type "m2" after the area. To list an area in square kilometers, use "km2" after the area. Example: Wikipedia shows that Seattle, WA, has an area of 369.2 km2 (or 142.5 sq mi). Instead of typing in a radius, which is not provided on Wikipedia, you could type "369.2 km2" or "142.5 m2" as the radius. It's important to include the "m2" or "km2" after the number so AQ knows that you aren't typing a radius! AQ will convert this to 8.08 miles radius. The actual radius, as returned by one geocoder, is 11.4 miles, so the area generates a result that's slighter smaller, but the important thing is to be approximately correct than precisely wrong! While 8.08 miles might be a little small, it's close enough for our purposes and is better than not providing an actual value at all.
Another thing that the radius is used for—when displaying maps showing your location, it determines how far to zoom in or out on the map. A location with a radius close to 0 will be zoomed in to the maximum extent possible, while a large radius of dozens of miles might zoom the map out to show the entire state, or an even larger radius of several hundred miles might show most of the entire country.