Coriopolis uses the standard gyrealm geographic coordinate system, adapted to the specific geometry of its 80-kilometer-long cylinder. Understanding this local implementation is essential for navigation, addressing, and environmental management within the habitat.

North–South Directions#

The north–south axis is aligned with the rotation axis of the cylinder. The north end is determined by the right-hand rule: curling the fingers of the right hand in the direction of Coriopolis’s rotation points the thumb toward the north end, which holds the cityscape. The south end, holding the nature preserve, is the opposite end of the rotation axis. This alignment is consistent throughout the length of the cylinder, providing a reliable reference for axial navigation.

As in every gyrealm, the convention preserves the terrestrial arrangement of the compass: facing north anywhere in Coriopolis, east lies to the right and west to the left. Seen from the axis by an observer who is not turning with the habitat, the interior rotates clockwise when looking north — the same relation Earth bears to its own poles.

East–West Directions#

East–west directions follow the curvature of the cylinder. West is the direction of rotation; east is against it. This cylindrical analogue of longitude is what keeps the habitat’s felt effects — the drift of falling water, the change in weight with travel — pointing the way terrestrial experience expects.

Zero Point#

The axial origin of the Coriopolis coordinate system is at the midpoint between the two ends of the cylinder, 40 kilometers from either end-cap, close to the midline ridge.

A cylinder supplies no natural circumferential origin, since every line drawn around it is equivalent, so the circumferential datum is fixed by convention: zero degrees longitude runs along Greenwich Avenue in the northern city. Longitude runs east and west from the avenue to 180° at the antimeridian.

Coordinate Notation#

Coordinates are expressed as a combination of axial (north–south) and circumferential (east–west) positions, with an optional level coordinate for vertical displacement from the main level. Axial position is given in kilometers north or south of the origin; circumferential position is given in degrees of longitude east or west of Greenwich Avenue. A point might accordingly be described as lying 20 kilometers north, 17° east.

Circumferential distances are also quoted metrically for engineering and transit work. Because a given arc length subtends a different angle at each radius, a metric circumferential position is ambiguous between levels where a longitude is not, and the degree form is preferred wherever a position must be unambiguous. At the floor, one degree is about 175 meters.

Application#

This coordinate system underpins urban planning, environmental management, transit, logistics, and everyday navigation in Coriopolis. Local convention numbers main-level structures at level zero, with upper levels positive and subsurface levels negative, consistent with the broader gyrealm standard.