Sure, Conformal Conic is used as the base-map for some states' plane coordinate systems. The parallels of that Conformal Conic are of course, as you said, centered in the state.Piotr wrote:"Cylindrical equal-area couldn't have an arbitrary standard parallel as its equator, because its equator has to be a great circle."
No. What I mean is stretch this projection to make a standard parallel coincide with small region you want to view.
And some countries (I haven't heard about it for U.S. states) use an oblique Mercator, whose "equator" goes through the middle of an oblong country, coinciding with its mid-line along its long-axis.
Those two adaptations are the sort of thing that you were referring to.
Of course that would be a good solution for a country that isn't oblong. You're referring to an azimuthal projection. The Stereofraphic would be used, because surveying and routefinding call for a conformal map. As I mentioned, Stereographis was used as the base-map for the polar regions in the UTM system.An alternate method that works for all projections with a point without angular distortion is to recenter the map so that the country is on that point.
It seems to me that Stereographic would be a fine choice for a non-oblong country, for the base-map for its plane-co-ordinate system--or for maps of that country for navigational or surveying purposes.
We sometimes encounter Azimuthal Equal-Area maps of the U.S., and so it wouldn't be so surprising if there were a Stereographic map of the U.S, for navigational or surveying purposes (Well, surveying is something that uses large-scale, small-region maps, I guess).
But air-navigation maps usually are Conformal Conic, because they neatly fit together in a big system of navigational maps.
And, as I mentioned, I suppose that surveying uses large-scale maps of small regions.
Michael Ossipoff