In projective geometry it may be defined as the conic which intersects the line at infinity in two real points, or to which it is possible to draw two real tangents from the centre.
Tsaritsyn is the terminus of a railway which begins at Riga and, running south-eastwards, intersects all the main lines which radiate from Moscow to the south.
The most striking physical feature is the Aravalli range of mountains, which intersects the country almost from end to end in a line running from south-west to north-east.
The principal river is the Trent, which, rising in the Staffordshire moorlands, intersects the southern part of Derbyshire, and forms part of its boundary with Leicestershire.
These orthodromic distances are of course shorter than those measured along a loxodromic line, which intersects all parallels at the same angle.