GLOBAL KNOWLEDGE ARK

Reference library

Foundations

Explore concepts, laws, equations and methods, with clear explanations of their use and sources. Choose an area of study or find a specific entry.

More filters

Reference entries

Showing 1621–1650 of 1709 reference entries

Chemistry · PhysicsIntensive, extensive, specific and molar properties

Scaling the system amount is different from changing its state.

DefinitionChemistry · MeasurementRelative atomic mass and isotope composition

Relative atomic mass is dimensionless and depends on the isotope composition being averaged.

DefinitionChemistry · MeasurementMolar mass and mass–amount conversion

Molar mass converts a specified substance's amount into mass.

DefinitionChemistry · MeasurementAmount concentration, molality and composition fractions

Concentration must declare its numerator and denominator.

DefinitionChemistryDilution conserves the retained solute amount

Dilution arithmetic refers to final solution volume, not the amount of solvent poured in.

MethodChemistryLimiting reagent, theoretical yield and percent yield

Stoichiometry gives a maximum under a specified reaction model; recovery measures the actual yield.

MethodChemistryFormal charge is equal-share electron accounting

Formal charge, oxidation state and partial charge answer different questions.

DefinitionChemistryElectrolyte strength, solubility and concentration

Strong describes ion formation by dissolved solute, not how much solute dissolves.

DefinitionChemistryComplete ionic and net ionic equations

Cancel unchanged species while conserving both atoms and charge.

MethodBiology · ChemistryWater polarity and biological interactions

Water's molecular interactions help explain solvation, cohesion and thermal buffering.

Empirical findingBiologyCell size and surface-to-volume scaling

For geometrically similar cells, volume grows faster than surface area.

ModelBiology · ChemistryOsmolarity and tonicity

Total particle concentration and lasting cell-volume effect are different properties.

DefinitionBiologyChromosome sets and DNA content

DNA replication doubles DNA content without doubling chromosome-set ploidy.

DefinitionBiologyOrganisms, populations, communities and ecosystems

Ecological levels describe different interacting sets and environments.

DefinitionBiologyPopulation size, density and demographic balance

Total individuals and individuals per area or volume must be distinguished.

ModelBiologyMutation and selection: different roles

Mutations do not generally appear because an organism needs their future advantage.

Empirical findingBiologyClades and rooted-tree interpretation

Shared ancestry is represented by topology, not by the left-to-right order of tips.

MethodBiology · ChemistryPlant water potential and pressure balance

Osmotic and mechanical contributions together determine passive water movement.

ModelEarth & cosmosRock and mineral are different material categories

A mineral species and a rock aggregate have different identifying features.

DefinitionEarth & cosmosEarth's compositional and mechanical layers

Crust–mantle–core and lithosphere–asthenosphere partition Earth by different properties.

ModelEarth & cosmos · MeasurementGeodetic latitude, longitude and reference systems

A coordinate pair needs a reference surface, origin and convention.

DefinitionEarth & cosmos · MeasurementMap projections and distortion

Flattening Earth's curved reference surface requires a choice of distortions.

ModelEarth & cosmos · MeasurementEllipsoid height, geoid and orthometric height

Height above a geometric reference is not automatically height above a gravity reference.

DefinitionEarth & cosmosRotation, axial tilt and seasonal sunlight

Axial tilt changes the angle and duration of sunlight in opposite hemispheres.

ModelEarth & cosmosNatural hazard and disaster risk

A harmful physical process and the potential losses it creates are different quantities.

DefinitionEarth & cosmosUsing present processes to infer Earth's past

Modern process evidence informs geological interpretation only with the past boundary conditions.

MethodEarth & cosmosLunar phases and synchronous rotation

Phases change the visible illuminated fraction; they are not Earth's shadow moving across the Moon.

ModelEarth & cosmosSolar and lunar eclipse geometry

New or full Moon is necessary for the corresponding eclipse but does not guarantee alignment.

ModelEarth & cosmosIAU Solar-System body categories

A scoped naming convention distinguishes planets, dwarf planets, small bodies and satellites.

DefinitionEarth & cosmos · MeasurementAstronomical unit and light-year

The astronomical unit and light-year measure lengths, with different defining conventions.

Definition
DefinitionSource checked

Geodetic latitude, longitude and reference systems

Earth & cosmosMeasurement

A coordinate pair needs a reference surface, origin and convention.

Key knowledge

Geodetic latitude measures the angle between the reference ellipsoid's normal and its equatorial plane; longitude measures the angle from a specified reference meridian. A coordinate is meaningful with its coordinate reference system and, when relevant, epoch. Geodetic latitude is distinct from the geocentric angle measured from Earth's center.

Conditions and scope

  • Identify the datum/reference frame, ellipsoid, angular units and longitude convention.
  • The definition uses an ellipsoidal reference, not a claim that Earth's terrain or geoid is exactly an ellipsoid.
Sources · 2

References

Sources retain their recorded scope. A source link alone does not establish verification of every statement.

  1. A Guide to Coordinate Systems in Great Britain, v3.6 (2020), §§1.2 and 3.1Ordnance SurveyReference guide · PDFordnancesurvey.co.ukRead source
  2. Ellipsoidally referenced surveys: reference systems and vertical datumsNOAA Office of Coast SurveyReference guidenauticalcharts.noaa.govRead source

Evidence and review

Inspected Ordnance Survey §§1.2 and 3.1.1, printed pp.6 and 12, latitude/longitude and reference-system definitions, and NOAA reference-system paragraphs. No national transformation algorithms or present-day datum replacement schedules are certified.

2026-10-10 · Independent Mathematics and Information editor (/root/core_math_information). Independent AI editorial review of this entry's statements, equations, applicability conditions and source coverage. Source checks apply to these claims within their stated limits.

Related reference entries

Explore relationships within this area of study and its connections to other areas.

Showing 1–4 of 4 relationships

Scientific relationships · 4 / 4

The relationship type describes the connection. Its linked statements, sources and conditions define the scope.

  1. Related to
    Relationship sources · 2

    Linked statements

    • Geodetic latitude measures the angle between the reference ellipsoid's normal and its equatorial plane; longitude measures the angle from a specified reference meridian. A coordinate is meaningful with its coordinate reference system and, when relevant, epoch. Geodetic latitude is distinct from the geocentric angle measured from Earth's center.

    Ellipsoidal coordinates and gravity-referenced heights need explicitly compatible reference surfaces.

  2. Related to
    Relationship sources · 2

    Linked statements

    • Geodetic latitude measures the angle between the reference ellipsoid's normal and its equatorial plane; longitude measures the angle from a specified reference meridian. A coordinate is meaningful with its coordinate reference system and, when relevant, epoch. Geodetic latitude is distinct from the geocentric angle measured from Earth's center.

    Mapped geological observations require a declared positional reference; latitude/longitude is not the strike/dip orientation of a plane.

  3. Related to
    Relationship sources · 3

    Linked statements

    • A map projection assigns positions on a curved Earth reference surface to a plane. Over finite curved regions, a flat map cannot preserve every distance, area, shape and direction simultaneously. Equal-area, conformal and equidistant projections preserve different specified properties; equidistant does not mean that every pair of mapped points has its true distance.

    Flattening coordinates and specifying their underlying reference system are distinct parts of a geographic representation.

  4. Related to
    Relationship sources · 1

    Linked statements

    • In equatorial sky coordinates, declination is angular position north or south of the reference equatorial plane; right ascension is measured eastward around that plane from a specified zero direction. The traditional zero uses the northward equinox crossing, but modern reference systems can fix axes independently of Earth's instantaneous equator and equinox. Catalog positions also have a reference epoch, with proper motions used to propagate changing directions. These two angles specify direction, not distance.

    Both terrestrial and celestial angular coordinates require a reference system; their planes and origins differ.

Entry detailsPermanent link to this entry ↗
Record identity
foundation-earth-geodetic-coordinates
Revision
foundations-refresh.1
Structured reference record
Foundational reference additions