Want to do an interesting experiment regarding circles and tangent lines? Lets inscribe a circle in a shape. A square will produce four tangents, an octogon eight, a dodecahedron, twelve. As you increase the number of lines, and the limit approaches infinity, so too does the number of tangent lines. In short, a circle is a polygon with infinite infintesimal sides and angles. Thus, when you take the vectors of these houses, the variation in the angle between them is something extraordinarily tiny (after all, a large house is 20 meters long, and given that the earth's circumfrence 39891240 meters, this creates an angle so infintesimal that we cannot possibly measure it without calculating it. It makes it hard to declare houses to be on the "same vector," especially when the earth's surface is dotted with hills and mountains and rivers and oceans and lakes as well.