longitude
Let an agent explain longitude and how it is defined and measured, relay history, conventions and reference meridians from geodesy and navigation sources, describe uses in mapping and time zones, and distinguish longitude from latitude, from local time and from celestial longitude.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
written by Claude from model knowledge without web access - no source was read, every claim is a lead to verify
Researched by: Claude
Purpose and description
Let an agent explain longitude and how it is defined and measured, relay history, conventions and reference meridians from geodesy and navigation sources, describe uses in mapping and time zones, and distinguish longitude from latitude, from local time and from celestial longitude.
The geographic coordinate that specifies east-west position on the Earth as an angle from the prime meridian at Greenwich, ranging from 0 to 180 degrees east and west, so that east longitude covers the Eastern Hemisphere, measured historically by chronometers and lunar distances and today by satellite positioning, and paired with latitude to locate any point; longitude also appears in celestial and planetary coordinate systems.
What it is for: Locating east-west position.
It can be explain definition and conventions; relay measurement and history; describe uses; distinguish related quantities.
Distinguishing features
Angular east-west coordinate
Arbitrary prime meridian
Time relation
Historically hard to measure
What it looks like
Not a visible object; meridian lines on a globe.
Physical character
range: 0-180 degrees east and west
prime meridian: Greenwich, IERS reference meridian note
one degree at the equator: about 111 km
Longitude Act: 1714 year - British prize
How it is recognised
East-west angular position from the prime meridian
East and west longitude, 0 to 180 degrees
Latitude is north-south; local time depends on longitude; celestial longitude is on the sky
Related models
is a kind of - in registry terms
is paired with - to locate points
is measured from - at Greenwich
determines - in principle
In practice
Families and kinds
east longitude
west longitude
geodetic longitude in modern datums
historical longitude from chronometers and lunar distances
celestial and planetographic longitude
Standards and regulation
IERS reference meridian and WGS 84
ISO 6709 for coordinate representation
International Meridian Conference of 1884
Failure modes and hazards
Sign and hemisphere confusion
Datum differences between historical and modern longitude
Registry alias ZGD is an unclear code
Also called
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 4 bundles · 8 layers · 8 findings · 16 questions.
Understand What longitude is.
Science.
Definition
Definition.
Definition
Definition.
- What is longitude, how is it measured from the prime meridian, and how does it differ from latitude? definition
- Is the question about geographic longitude, time, celestial coordinates or history? boundary
Conventions
Conventions.
Conventions
Conventions.
- How are east and west longitude, signed values and the 180th meridian handled? definition
- Which entry fits geographic coordinate system? action
Measure Measurement.
Practice.
Modern
Modern measurement.
Modern
Modern.
- How do GNSS and geodetic datums determine longitude today? measurement
- Which references are standard? provenance
Historical
Historical measurement.
Historical
Historical.
- How were chronometers and lunar distances used to find longitude at sea? provenance
- Which sources are cited? provenance
Use Uses.
Application.
Mapping
Mapping and navigation.
Mapping
Mapping.
- How is longitude used in maps, charts and navigation? provenance
- Which entry fits navigation? action
Time
Time zones.
Time
Time.
- How does longitude relate to solar time and time zones? provenance
- Which entry fits time zone? action
Context History and beyond Earth.
Context.
History
History.
History
History.
- How was the longitude problem solved, from the Longitude Act to Harrison and the 1884 conference? provenance
- Which entry fits the history of longitude? action
Planets
Other bodies.
Planets
Planets.
- How is longitude defined on the Moon, Mars and the celestial sphere? provenance
- Which entry fits planetary coordinate system? action
What the second pass must settle
- Should prime meridian and the history of longitude be separate primary entries?
- How should geodesy sources be linked?
- The registry alias ZGD should be reviewed