Northern Hemisphere
Enable an AI agent to recognise Earth's Northern Hemisphere, determine whether locations or spatial extents belong to it, and judge when hemispheric comparisons or actions are valid.
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.
Researched by: Codex + Grok
Purpose and description
Enable an AI agent to recognise Earth's Northern Hemisphere, determine whether locations or spatial extents belong to it, and judge when hemispheric comparisons or actions are valid.
The Northern Hemisphere is the half of a celestial body, conventionally Earth, lying north of the equatorial plane, bounded by that plane and containing the North Pole.
It can be Classify a terrestrial point as northern, southern, equatorial or unresolved.; Intersect a route, polygon or raster with the northern extent using a declared boundary rule.; Calculate the northern share of a cross-equatorial feature using an appropriate spatial measure.; Filter or aggregate observations over a declared Northern Hemisphere extent.; Check whether a hemispheric comparison uses compatible coverage, weighting and time periods.; Flag unsupported transfers from hemisphere membership to local climate, season or socioeconomic status..
Distinguishing features
Its defining division is Earth's equator, rather than a political, economic or cultural boundary.
Positive latitude identifies its interior under a stated terrestrial latitude convention; zero latitude requires an explicit boundary rule.
It includes the North Pole and excludes the South Pole.
Its extent spans all longitudes, so longitude alone cannot establish or exclude membership.
It denotes a terrestrial spatial extent, rather than the part of the celestial sphere north of the celestial equator.
Scope
+ Identity of Earth's Northern Hemisphere relative to the equator and North Pole
+ Latitude reference and treatment of the equatorial boundary
+ Membership and overlap of points, routes, areas and spatial datasets
+ Coverage and comparability of observations aggregated over the Northern Hemisphere
+ Limits on interpreting seasonal or environmental patterns at hemispheric scale
- The northern celestial hemisphere and astronomical coordinate systems
- The Southern Hemisphere as an independently described region
- Countries, jurisdictions and their administrative authority
- Detailed climate, weather and ecological processes
- The Global North as a socioeconomic grouping
- Northern hemispheres of other planets or bodies
Characteristics
- Reference body
- Earth Distinguishes this registered thing from similarly named regions of other bodies.
- Latitude reference
- Declared coordinate reference system and latitude type, such as geodetic or geocentric Makes numerical positions and boundary calculations interpretable.
- Interior latitude range
- Degrees north: greater than 0 through 90 Provides the primary point-membership test.
- Equator inclusion convention
- Included boundary | excluded boundary | separately classified boundary Prevents inconsistent treatment or double counting of equatorial features.
- Spatial relationship to the hemisphere
- Wholly inside | wholly outside | crosses equator | touches equator | indeterminate Supports classification of extended features without reducing them to a representative point.
- Northern share of a spatial extent
- 0-1 or percent, with area or length basis and calculation method stated Allows cross-equatorial regions and routes to be apportioned for a particular task.
- Observation coverage
- Percent of declared hemispheric target area and time interval, with sampling basis Distinguishes hemispheric evidence from observations of a limited northern subset.
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 5 bundles · 9 layers · 16 findings · 24 questions.
Terrestrial Hemisphere Identity Establishes which northern hemisphere the entry denotes and what defines its extent.
The name can refer to terrestrial, celestial or other planetary regions, while the registry supplies no definition.
Earth and Equatorial Division
Anchors the concept to Earth and its equatorial division.
Earth North of the Equator
Record whether the intended referent is the terrestrial region extending northward from the equator to the North Pole.
- Does the registry intend Earth's geographic Northern Hemisphere? definition
- Which authoritative definition supports the equator and North Pole as its defining limits? provenance
Nearby Northern Concepts
Separates geographic membership from similarly named astronomical and socioeconomic concepts.
Geographic North Disambiguation
Record contextual evidence distinguishing this extent from the northern celestial hemisphere, Global North and locally defined northern regions.
- Does the usage describe terrestrial latitude, celestial position or a socioeconomic grouping? definition
- When a source says only 'the north', what evidence permits linking it to this registry entry? boundary
Equator and Coordinate Membership Defines reproducible membership decisions near the equator and at coordinate singularities.
Latitude sign is useful only when the coordinate convention, uncertainty and equator treatment are explicit.
Latitude Membership Test
Connects terrestrial coordinates to a northern membership decision.
Latitude Sign and Reference
Record the coordinate reference, north-positive convention and positional uncertainty used to classify a point.
- Which coordinate reference system and latitude type describe the position? measurement
- Does the position's uncertainty interval remain north of zero latitude or cross the equator? boundary
Equatorial and Polar Cases
Handles zero latitude, the North Pole and longitude wraparound consistently.
Boundary and Pole Policy
Record how equatorial positions are assigned and ensure that polar or antimeridian representations do not distort hemispheric membership.
- Are positions exactly on the equator included, excluded or assigned to a separate boundary class? boundary
- How will the agent preserve North Pole membership and handle antimeridian-crossing geometry despite longitude representation issues? action
Cross-Equatorial Spatial Operations Supports operations on features that occupy or traverse both hemispheres.
Countries, oceans, routes and raster cells cannot reliably be classified from a name or centroid alone.
Extended Feature Membership
Distinguishes whole-feature inclusion from partial overlap and equator contact.
Feature-Equator Relationship
Record whether the actual geometry lies north, south, across or along the equator, including disconnected components.
- Does any part of the feature cross or touch the equator, including detached islands or separate geometry components? boundary
- Does the task require whole-feature inclusion, any northern overlap or clipping to the northern portion? action
Northern Portion Calculation
Defines how the northern contribution of an extended feature is measured.
Hemispheric Apportionment
Record the measure, geometry method and boundary allocation used to calculate a feature's northern share.
- Is the northern share measured by surface area, route length or another task-specific quantity? measurement
- How are equator-crossing raster cells or spatial totals apportioned without assuming an unsupported uniform distribution? action
Hemispheric Evidence and Interpretation Governs the use of the Northern Hemisphere as an observational and comparative extent.
A hemispheric label can conceal incomplete coverage and does not establish uniform seasonal or environmental conditions.
Hemispheric Observation Coverage
Checks what a purported Northern Hemisphere observation actually covers.
Coverage and Weighting Basis
Record spatial masks, latitude coverage, time interval and weighting before treating a statistic as hemispheric.
- Does the evidence cover the full northern extent or only selected land, ocean, latitude bands or observing stations? measurement
- Which weighting method and time interval make the aggregate suitable for the proposed hemispheric comparison? measurement
Seasonal and Local Inference Limits
Separates a northern spatial classification from claims about conditions at a particular location.
Hemisphere Is Insufficient Local Evidence
Record the seasonal convention and local evidence needed before applying a hemispheric statement to a tropical, temperate or polar location.
- Does a seasonal claim use astronomical, meteorological or locally defined seasons? definition
- What latitude-specific and local evidence is required before using a hemispheric pattern to guide an action at this location? action
Evidence and external alignment What the world already says about this thing, gathered so the model can be checked against it.
A model that cannot be lined up against existing standards, identifiers and practice cannot be adopted by anyone who already uses them.
Reported evidence
Findings from the breadth pass, kept separate from the structural claims.
Kinds and varieties
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Terrestrial Northern Hemisphere (Earth, geographic)
- Celestial Northern Hemisphere (sky north of the celestial equator)
- Celestial Northern Hemisphere of other planets (planetary cartographic north)
- Magnetic Northern Hemisphere (Earth, geomagnetic)
- Seasonal Northern Hemisphere (meteorological / climatic usage)
- Which of these kinds and varieties hold for the sense of Northern Hemisphere this model covers, and on what evidence? provenance
Identifiers and schemes
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Wikidata - Q39061 - Northern Hemisphere (Earth, geographic)
- Which of these identifiers and schemes hold for the sense of Northern Hemisphere this model covers, and on what evidence? provenance
Standards and regulation
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- IAU Working Group for Planetary System Nomenclature - planetary north and coordinate systems
- ISO 19111 / ISO 6709 - geographic coordinate referencing (equator as dividing plane)
- WMO - meteorological products and seasonal definitions by hemisphere
- Which of these standards and regulation hold for the sense of Northern Hemisphere this model covers, and on what evidence? provenance
Real-world use
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Climatology and meteorology: NH as a domain for circulation, monsoon, and seasonal forecasts
- Astronomy: celestial northern hemisphere for star charts, constellations, and observatory siting
- Geodesy and mapping: north-of-equator half of Earth in lat/long products
- International law and aviation/maritime practice: routes, time, and seasonal rules that differ north of the equator
- Which of these real-world use hold for the sense of Northern Hemisphere this model covers, and on what evidence? provenance
Typical measurements
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Latitude span - 0 to +90 - degree
- Surface area (Earth land+ocean) - about 2.55e8 - km^2
- Land fraction of Earth's land - about 67-68 - percent
- Which of these typical measurements hold for the sense of Northern Hemisphere this model covers, and on what evidence? provenance
Failure modes and hazards
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Confusing geographic north with magnetic north when assigning 'northern' domains
- Applying NH seasonal calendars (e.g. DJF winter) in the Southern Hemisphere or tropics
- Planetary cartography: using Earth's geographic north instead of IAU-defined north on other bodies
- Which of these failure modes and hazards hold for the sense of Northern Hemisphere this model covers, and on what evidence? provenance
Regional variation
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Tropical countries often do not treat 'Northern Hemisphere' as a lived seasonal category
- Some popular usage treats 'the North' as a political/economic bloc, not the geographic hemisphere
- Which of these regional variation hold for the sense of Northern Hemisphere this model covers, and on what evidence? provenance
Neighbouring kinds and how to tell them apart
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Northern Hemisphere (celestial) - Sky north of the celestial equator vs. Earth's surface north of the geographic equator; a place can be in Earth's NH while observing southern-sky objects.
- Northern polar region / Arctic - Arctic is a high-latitude region (commonly ~66.5°N to pole), not the entire hemisphere north of 0°.
- Geomagnetic northern hemisphere - Divided by the geomagnetic equator, which is offset from the geographic equator.
- Global North (development/politics) - Socioeconomic grouping (Brandt line etc.), not a geometric half of the planet.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of Northern Hemisphere this model covers, and on what evidence? provenance
Sources
- Gazetteer of Planetary Nomenclature - Coordinate Systems - IAU/USGS planetary cartographic convention for defining north and hemispheres on other bodies.
- WMO - Meteorological seasons - Operational use of Northern Hemisphere as a meteorological domain and seasonal calendar (DJF winter).
What the second pass must settle
- Does the registry's XCT / XCT.QLT placement intend the terrestrial region, a spatial classification or another meaning of Northern Hemisphere?
- Does an existing Vercy world model already own this concept and require a registry link instead of a separate publication?
- Which authoritative geographic and geodetic sources should establish the definition and coordinate conventions?
- Should the catalogue adopt one equator-inclusion rule, or require each spatial operation to declare its own?
- Does the intended extent cover only Earth's surface, or must atmospheric, subsurface and near-Earth observations be associated through a separately defined projection rule?