3 mile jurisdiction

[JoshWhite]

I've created a 3 mile buffer around the city for our city's extraterritorial jurisdiction but I've learned of a new statute concerning a small city that sprung up next to ours.  The statute reads that you can only go half the distance to the city instead of the full 3 miles.  So to simplify this, when somebody wants to do a subdivision, currently I would have to measure the distance to each of the cities to determine which one it is closest to.  If it is closer to mine than I have jurisdiction, if not, I don't have jurisdiction.  My question is, does anyone know of a way to map this?

[TrishRice]

So you want to map the buffer around your city, trimmed on one side at the halfway point with the other city?  You could make a Thiessen polygon around your city and then Union it with your 3 mile buffer.  You need a layer of both cities' limits.  (This is assuming the limits are irregular and the halfway point is not already a convenient straight line.)

Now before you ask, I know Thiessen polygons are technically only for points.  But thanks to computers we can do this easily.  (Here's a topic when I was figuring out how to make polygons around my streets.)  Basically you turn all the city limits into a whole bunch of points at a convenient spacing, run thiessen polygons on those, and merge the sliver polygons back together into one big polygon for each city.