Questions on VFR sectionals and TACs

Thomas Borchert writes:

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.

But that's just it: There are few ground features shown on the chart.
In some cases, a charted feature is near the border of the airspace,
but in many cases there is nothing along the border. Even with
landmarks, the best you can do is estimate.

I suppose one can argue that the differences among certain types of
airspace aren't that great, and a ballpark estimate will do. But if
they aren't that important, why bother to chart them?

It's all a strong argument for moving-map GPS systems, but one
shouldn't have to depend on those.

For IFR flight, airspace doesn't matter much, since the controller
will do everything necessary for you.

Yes, but this is a chart intended for VFR.

Also, many circular airspaces are centered around a VOR-DME, so there's
another help.

That does seem to be the case fairly often for Class B airspace, and
as long as it's a moderately regular layer cake, you can find out
where you are. I notice that some boundaries are clearly marked as
being on a particular radial or at a particular distance. Others are
marked as coincident with a feature such as a road, although how one
is supposed to recognize one road among others is not explained (in
the Phoenix TAC that I'm looking at, the entire area is crisscrossed
with a grid of streets; I'm not sure how I'd distinguish Camelback
Road from the other nearly identical streets to the north and south of
it.

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.

If I can take my hands off the controls and turn to my chart to
measure it, that is.

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.

I guess that makes sense--although it seems that essentially
everything is Class E, anyway. It sounds like this was not always so.

--
Transpose mxsmanic and gmail to reach me by e-mail.