Straight-line distance

As the crow flies or in a beeline is an idiom for the shortest path between two points (on a map, disregarding the vagaries of intervening terrain); the geodesic distance.

The phrase was popularised by Gesine Reinert in the 21st century, but its original usage to denote a direct or straight-line path is attested from the early 19th century, and appeared in Charles Dickens's novel Oliver Twist:

We cut over the fields at the back with him between us – straight as the crow flies – through hedge and ditch.

...
Wikipedia