The geographic coordinate system used in gyrealms is the standard framework for navigation, orientation, and mapping within these rotating cylindrical habitats. Designed to accommodate the physical properties of a rotating reference frame, it combines principles from spherical and cylindrical coordinate systems with adaptations specific to gyrealm geometry.

Basic Principles#

The system uses axial and circumferential coordinates analogous to longitude and latitude on Earth, supplemented by a level coordinate that replaces altitude.

North–South (Axial Coordinate)#

The axial coordinate runs along the length of the cylinder from one flat end to the other. North and south are determined by rotation: using the right-hand rule, curling the fingers of the right hand in the direction of the cylinder’s rotation points the thumb toward the north end. The south end is the opposite end of the rotation axis. This alignment is consistent throughout the interior, providing a reliable reference for axial navigation.

East–West (Circumferential Coordinate)#

The circumferential coordinate follows the curvature of the cylinder. East is the direction of rotation; west is against it. This creates a cylindrical analogue of latitude that matches inhabitants’ perception of their environment, since the rotation is directly felt.

Zero Point#

The origin is located at the midpoint between the two ends of the cylinder, serving as the reference for both axial and circumferential coordinates.

Level Coordinate#

The level coordinate replaces traditional altitude, describing distance from the main level of the habitat. The main level is set at zero; structures above or below are assigned positive or negative level values.

Coordinate Notation#

Positions are expressed as a combination of axial, circumferential, and level values. For example, a location might be described as “20 kilometers north, 5 kilometers east of the origin, and 2 levels above.”

Challenges and Adaptations#

Mapping a flat coordinate system onto a rotating cylindrical surface introduces complications, including Coriolis and centrifugal effects that shift apparent paths of motion. Navigation software and transit systems use specialized algorithms to convert between coordinates and actual movement vectors within the rotating frame.

Importance and Usage#

The coordinate system underpins every aspect of life in a gyrealm: urban planning, environmental management, transportation, addressing, logistics, and emergency services. Individual habitats may tune parameters such as the location of the origin or the numbering of levels to local convention, but the fundamental axial–circumferential–level scheme is universal across the civilization.