Questions on VFR sectionals and TACs

Mxsmanic,

It's just hard to figure out whether I'm inside or outside the
boundaries without a radius and center point.


You're going at this the wrong way. In flight, what you do is simply
look at the chart, find some ground features close to the border line
of the airspace, look out the window, find the same ground features -
and presto, you know where you are in relation to the airspace. For IFR
flight, airspace doesn't matter much, since the controller will do
everything necessary for you.

Also, many circular airspaces are centered around a VOR-DME, so there's
another help. Figuring the radius (which is normally standardized for
certain types of airspace) is pretty easy, since the scale of a
sectional is the same every time and you have a ruler.

The logic for class E lower limits is in IFR traffic being in it. Class
E means higher visibility requirements for VFR, so they can separate
themselves from IFR traffic. You may recall the thread in which we
tried VERY HARD to make you understand that concept. If you still
haven't grasped it, it's no surprise you don't understand the logic of
Class E lower limits. What comes round...

--
Thomas Borchert (EDDH)