Height is the vertical distance from a chosen base, reference level or lower point to an upper point. If you are asking “what is height?”, the everyday answer is how tall something is, but the complete concept depends on the reference: triangle height, body height, building height, mountain elevation, aircraft height, fluid-column height and image height all use different conventions.

A complete explanation of height must distinguish height from length, width, depth, elevation and altitude. Length can point in any direction. Height is tied to a chosen vertical. Elevation describes vertical position relative to a datum. Altitude is used for position above a reference surface. These distinctions matter because the same object can have one physical length but a different vertical height when tilted.

This guide explains height from first principles: geometry, trigonometry, construction, surveying, geodesy, terrain, aviation, physics, fluids, biology, medicine, architecture, structural engineering, manufacturing, logistics, graphics, computer vision, robotics, GIS, data science and uncertainty. The goal is a durable operating model: define the base, vertical direction, datum and units before treating any height as comparable.

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What Is Height? A Short Definition

Height is the vertical distance from a chosen base, reference level or lower point to an upper point. In geometry, height is usually measured perpendicular to a base. In everyday life it can describe a person’s stature, a building’s elevation, the height of a mountain or the vertical size of an object.

Why Height Matters

Height determines clearance, stability, capacity, visibility, pressure, potential energy and scale. Architects use height for rooms and buildings, engineers use it for structures and fluids, doctors record body height, geographers compare elevations and computer graphics uses height values to construct terrain and depth.

Height Versus Length

Length is any one-dimensional extent, while height is the component measured along a chosen vertical direction. An object can keep the same length while its height changes when tilted.

Height Versus Width

Width measures transverse extent, while height measures vertical extent under a chosen orientation. Rotating an object can exchange which physical dimension is called width or height.

Height Versus Depth

Depth often measures inward or downward extent from a surface, whereas height measures upward extent from a base or reference. Both are linear distances but use different directional conventions.

Height Versus Elevation

Height measures vertical separation between two points; elevation usually describes vertical position relative to a datum such as mean sea level or another reference surface.

Height Versus Altitude

Altitude generally describes vertical position above a reference level, commonly sea level or terrain in aviation contexts. Height often measures the object’s own vertical extent or distance above a local base.

Height Versus Stature

Stature is a biological or anthropometric use of height for a person’s standing body measurement under a defined posture and protocol.

Height in Geometry

Geometric height is usually a perpendicular distance from a base, line or plane to an opposite point or parallel feature. The perpendicular requirement matters because a slanted side is not automatically the height.

Triangle Height

A triangle’s height is the perpendicular distance from a chosen base to the opposite vertex. Different choices of base produce different heights while preserving the same area.

Altitude of a Triangle

A triangle altitude is the segment from a vertex perpendicular to the line containing the opposite side. It may lie inside or outside an obtuse triangle.

Triangle Area and Height

Triangle area is one half base times perpendicular height. Using a slanted side instead of the perpendicular height gives an incorrect result unless that side happens to be perpendicular.

Parallelogram Height

A parallelogram’s height is the perpendicular distance between its parallel bases. Shearing the shape changes side angles but can preserve base and height and therefore area.

Trapezium Height

The height of a trapezium or trapezoid is the perpendicular separation between its parallel sides. This height appears in the area formula.

Rectangle Height

Rectangle height is one side dimension chosen as vertical relative to the diagram or application. Since rectangles can be rotated, height is conventional rather than intrinsic.

Prism Height

Prism height is the perpendicular distance between its parallel congruent bases. Volume equals base area times this height.

Cylinder Height

Cylinder height is the perpendicular distance between its circular bases for a right circular cylinder. It determines volume together with radius.

Pyramid Height

Pyramid height is the perpendicular distance from the apex to the plane of the base. Slant height is different and runs along a face.

Cone Height

Cone height is the perpendicular distance from apex to base plane. Slant height follows the side surface and is longer unless the cone degenerates.

Slant Height

Slant height measures along the inclined surface of a cone or pyramid. It is used in lateral-area formulas and should not be confused with perpendicular height.

Height of a Sphere

A sphere’s total vertical height equals its diameter when measured through the centre. Any orientation gives the same maximum extent because of spherical symmetry.

Height of a Segment

A circular segment height, often called sagitta, measures from the chord to the arc along the perpendicular through the chord midpoint.

Height and Coordinate Geometry

In Cartesian coordinates, vertical height difference is often the absolute difference in y or z coordinates depending on axis convention. The coordinate frame must be stated.

Height from Coordinates

If vertical is the y-axis, height difference between two points is |y2-y1| when only vertical separation is wanted. Straight-line distance is larger when horizontal displacement also exists.

Height and Vectors

Height can be found by projecting a displacement vector onto the vertical unit direction. This works in rotated coordinate systems and 3D geometry.

Height and Dot Product

The vertical component of a displacement is the dot product with a vertical unit vector. This separates height from other directional motion.

Height and Scale

Uniform scaling by factor k multiplies height by k. Areas then scale by k² and volumes by k³.

Height and Similarity

Similar shapes preserve ratios of corresponding heights. If one similar triangle is twice as large linearly, its height doubles.

Height and Trigonometry

Height can be calculated from distance and angle using sine, cosine or tangent. This is fundamental in surveying, navigation and construction.

Height from Angle of Elevation

If horizontal distance d and angle of elevation θ are known, height difference under flat right-triangle geometry is d tanθ.

Height from Sine

When line-of-sight distance L and vertical angle are known, vertical component can be L sinθ under the chosen angle convention.

Height from Shadows

Similar triangles allow object height to be inferred from shadow length when Sun angle or a reference object’s height and shadow are known.

Height from Similar Triangles

If two objects experience the same light geometry, height ratios equal shadow-length ratios under the ideal parallel-ray approximation.

Height and Pythagorean Theorem

In a right triangle, height can be derived from hypotenuse and horizontal base using the Pythagorean theorem.

Height in Construction

Construction relies on heights for storeys, ceilings, doors, stairs, walls, foundations and services. Reference datums and benchmarks keep vertical measurements consistent.

Floor-to-Floor Height

Floor-to-floor height is the vertical distance between corresponding finished or structural floor levels, depending on the stated convention.

Ceiling Height

Ceiling height is the vertical distance from finished floor to ceiling surface or underside under a defined measurement. Services and dropped ceilings can reduce it.

Clear Height

Clear height is unobstructed vertical space available for movement, equipment or storage. It can be less than nominal room height because of beams, ducts or fixtures.

Door Height

Door height defines vertical opening size. Frames, thresholds and floor finishes influence actual clear opening.

Window Height

Window height can refer to overall frame height, opening height or sill-to-head distance. Drawings should specify which.

Wall Height

Wall height may run from floor to ceiling, foundation to parapet or another construction reference. Irregular sites make one number insufficient.

Storey Height

Storey height usually includes structural floor depth and ceiling zone between successive levels, while clear room height excludes them.

Building Height

Building height depends on the regulatory or measurement convention. It might be measured to roof ridge, parapet, highest occupied floor or another reference.

Structural Height

Structural height describes the vertical extent of a structure according to engineering reference points. Antennas and nonstructural elements may be excluded depending on the definition.

Parapet Height

Parapet height is the vertical distance from adjacent roof or floor level to the top of the parapet. It affects safety and appearance.

Handrail Height

Handrail and guard heights are measured vertically from specified walking or floor surfaces under applicable regulations.

Stair Riser Height

Riser height is the vertical rise between consecutive stair treads. Consistent risers are important for comfort and fall prevention.

Total Stair Rise

Total rise is the overall vertical height between floor levels. Dividing it into equal risers determines stair count and individual rise.

Ramp Height

A ramp overcomes a vertical height difference over a longer horizontal run. Gradient connects rise and run.

Height and Slope

Slope can be expressed as height change divided by horizontal distance. Percent grade multiplies this ratio by one hundred.

Height in Surveying

Surveying determines elevations and height differences using levelling, total stations, GNSS and trigonometric methods.

Benchmark Height

A benchmark has a known elevation used as a vertical reference. Construction and mapping propagate heights from benchmarks.

Reduced Level

Reduced level is a surveyed elevation relative to a datum. Terminology varies by region, but the concept is vertical position relative to a reference.

Levelling

Levelling determines height differences using horizontal lines of sight and staff readings. It can achieve high precision over construction and engineering scales.

Trigonometric Heighting

Trigonometric heighting uses measured distance and vertical angle to infer elevation differences. Atmospheric refraction and instrument height can matter.

GNSS Height

GNSS commonly produces ellipsoidal height. Converting to a height related to mean sea level requires a geoid model or other vertical datum transformation.

Ellipsoidal Height

Ellipsoidal height measures distance along the ellipsoid normal from a reference ellipsoid to the point.

Orthometric Height

Orthometric height is related to the geoid and approximates conventional elevation above mean sea level. It differs from ellipsoidal height by geoid separation.

Height in Geography

Geography uses elevation, relief and terrain height to describe landforms and influence climate, drainage and ecosystems.

Mountain Height

Mountain height can mean summit elevation above sea level or topographic prominence relative to surrounding saddles. These are distinct measures.

Elevation Above Sea Level

Elevation gives vertical position relative to a chosen sea-level-related datum. It is not the same as local height above nearby ground.

Topographic Prominence

Prominence measures how far a summit rises above the lowest contour connecting it to higher terrain. It captures independent relief rather than absolute elevation.

Topographic Relief

Relief is the difference between high and low elevations within an area. It summarises vertical terrain variation.

Height Above Ground

Height above ground level measures local vertical separation from terrain to an object. Aviation and structures often distinguish this from altitude above sea level.

Tree Height

Tree height is measured from ground base to highest point. Clinometers, lidar and photogrammetry can estimate it, but canopy shape and slope add uncertainty.

Canopy Height

Canopy height can mean top-of-canopy elevation minus ground elevation, often derived from lidar or remote sensing.

Height in Remote Sensing

Radar, lidar and photogrammetry infer surface heights from signal travel, geometry or image matching. Each method has characteristic errors.

Lidar Height

Lidar provides 3D point clouds. Comparing vegetation returns with ground returns produces tree and canopy height estimates.

Radar Height

Radar altimetry measures range to a surface using radio waves. Surface roughness and atmospheric effects influence accuracy.

Photogrammetric Height

Overlapping images allow 3D reconstruction through parallax. Camera calibration and ground control determine height quality.

Height in Aviation

Aviation distinguishes altitude, height above terrain, flight level and pressure altitude. Using the correct vertical reference is essential for safety.

Altitude

Altitude generally refers to vertical distance above a reference such as mean sea level. Exact operational definitions depend on aviation procedure.

Height Above Terrain

Height above terrain or ground measures vertical clearance from the surface below. Terrain varies continuously, so the reference changes along a flight path.

Flight Level

Flight levels are pressure-based surfaces referenced to a standard pressure setting rather than direct geometric height.

Pressure Altitude

Pressure altitude is altitude indicated relative to standard atmospheric pressure and is used in performance and flight-level systems.

Radar Altitude

Radar altimeters measure height above terrain directly beneath an aircraft using radio signals, useful during low-altitude flight.

Height in Spaceflight

Spacecraft altitude is distance above a reference planetary surface or ellipsoid, while orbital radius is measured from the body’s centre.

Height in Physics

Height enters gravitational potential energy, hydrostatics, projectile motion and fluid columns. Its meaning is always relative to a chosen reference.

Gravitational Potential Energy

Near Earth’s surface under a constant-g approximation, potential-energy change is mgh, where h is vertical height difference.

Height and Gravity

At large height changes, gravitational acceleration varies, so simple mgh becomes an approximation rather than an exact universal formula.

Projectile Height

Projectile motion has vertical position changing with time under gravity. Maximum height occurs when vertical velocity reaches zero in the ideal model.

Maximum Projectile Height

For a given launch velocity component and constant gravity without drag, maximum height follows from kinematic relationships.

Height in Hydrostatics

Fluid pressure changes with vertical depth or height according to density and gravity under static conditions.

Pressure Head

Pressure head expresses pressure as an equivalent height of a fluid column, linking pressure with gravitational potential.

Hydraulic Head

Hydraulic head combines elevation, pressure and sometimes velocity terms to represent fluid energy per unit weight.

Water Column Height

A liquid column of greater height produces greater hydrostatic pressure at its base when density and gravity are constant.

Height in Atmosphere

Atmospheric pressure decreases with height because there is less air above. Temperature structure and weather make the exact relationship variable.

Scale Height

Atmospheric scale height is a characteristic vertical distance over which pressure or density changes substantially in an idealised exponential model.

Cloud Base Height

Cloud base height is the vertical distance from a reference level to the lowest visible cloud layer. Ceilometers and observation methods estimate it.

Wave Height

Wave height is vertical distance from trough to crest. Significant wave height is a statistical oceanographic measure based on a distribution of waves.

Tide Height

Tide height is water level relative to a chart or tidal datum at a time and place, not the vertical size of one wave.

Height in Biology

Biology uses height for stature, plant growth and organism dimensions. Measurement protocol matters because posture and growth conditions vary.

Human Height

Human standing height is measured from floor to top of head with standard posture, typically using a stadiometer.

Height and Age

Human height changes through growth and can decline slightly in later adulthood. Population reference charts describe distributions rather than individual destiny.

Height and Genetics

Human stature is influenced by many genes and environmental factors such as nutrition and health. It is a complex trait rather than a single-gene outcome.

Plant Height

Plant height is commonly measured from soil or stem base to the highest relevant point. Growth stage and leaning can affect the method.

Crop Height

Crop height can indicate growth and biomass but varies with species, density and environmental conditions.

Height in Medicine

Clinical height is used in body-mass index, growth monitoring, drug calculations and equipment sizing. Inaccurate measurement can propagate into derived quantities.

Stadiometer

A stadiometer is designed for standardized body-height measurement with a vertical scale and horizontal headpiece.

Recumbent Length

Infants or people unable to stand may have recumbent length measured horizontally rather than standing height. The methods are not perfectly interchangeable.

Height in Ergonomics

Workstations, shelves, controls and seats are designed around human height distributions and reach rather than one average person.

Eye Height

Eye height is the vertical position of the eyes above a support surface. It matters in sightlines, displays and driver visibility.

Shoulder Height

Shoulder height helps determine garment fit, workspace design and reach relationships.

Sitting Height

Sitting height measures vertical distance from sitting surface to top of head and informs seat, vehicle and cabin design.

Height in Architecture

Architects use height to shape proportions, views, daylight and spatial character. Tall spaces can feel open but cost more to condition.

Double-Height Space

A double-height space spans roughly two storeys and can improve visual connection and daylight while reducing floor area efficiency.

Height and Daylight

Window-head height influences how deeply daylight can penetrate a room. Orientation and shading matter as much as height.

Height and Ventilation

Vertical height supports stack-effect ventilation by creating pressure differences between lower and upper openings.

Stack Effect

Warm air buoyancy can drive airflow through tall spaces or shafts. Greater vertical separation can increase pressure difference under suitable thermal conditions.

Height in Structural Engineering

Column height, beam depth and building height affect buckling, lateral stability and dynamic response.

Column Height

Longer columns are more susceptible to buckling for the same cross-section and material, making effective length a critical design concept.

Effective Height

Effective height can differ from physical height because boundary conditions and restraint change structural behaviour.

Building Height and Wind

Wind speed and pressure often increase with elevation above ground, while tall buildings also experience dynamic effects and vortex shedding.

Height and Seismic Response

Building height influences natural periods and seismic behaviour, but stiffness, mass distribution and structural system also matter.

Height in Manufacturing

Machine setups use height gauges, tool heights and stack heights to control dimensions and assembly.

Height Gauge

A height gauge measures vertical dimensions from a reference surface, often on a surface plate.

Tool Height

CNC and machining systems store tool-length or height offsets so different tools reach the programmed reference correctly.

Stack Height

Stack height describes accumulated vertical dimension of assembled parts. Tolerance stack-up can make total height vary significantly.

Height in Packaging

Package height affects shelf fit, pallet stacking and dimensional shipping charges.

Pallet Height

Loaded pallet height includes pallet plus goods and must fit warehouse racks, vehicle doors and handling limits.

Container Internal Height

Shipping containers have specified internal height and door opening height. Cargo can fit internal volume yet fail to pass through the door.

Height in Warehousing

Rack height and lift height determine storage capacity. Safety and fire-clearance rules also constrain usable vertical space.

Rack Height

Rack height controls how many storage levels fit within a building, but handling equipment and sprinklers reduce theoretical capacity.

Lift Height

Forklifts and cranes have maximum lift heights tied to rated capacity and stability.

Height in Logistics

Vehicle and load height affect bridges, tunnels, loading bays and route choice.

Clearance Height

Clearance height is the available vertical gap under an obstruction. Safe routing requires margin beyond measured vehicle height.

Bridge Clearance

Bridge clearance can vary by lane, tide or resurfacing and should rely on authoritative current signage and data.

Height in Road Design

Vertical clearance, sightline height and roadside object height influence transportation safety.

Vehicle Height

Vehicle height includes roof equipment and loads. Dynamic suspension and tyre conditions can change actual clearance.

Height in Railways

Railway clearance envelopes account for vehicle height, overhead wires and movement. Static dimensions alone are insufficient.

Height in Marine Systems

Mast height, air draft and wave conditions determine whether vessels can pass under bridges.

Air Draft

Air draft is the vertical distance from waterline to highest point of a vessel. It changes with loading and water level.

Height in Electronics

Component height affects enclosure design, board stacking and cooling. Tall parts can interfere with lids or neighbouring boards.

Component Height

Electronics drawings specify maximum component height zones to avoid mechanical collision.

Height in Computer Graphics

Graphics uses height for viewport dimensions, image size, terrain elevation and object bounds.

Image Height

Image height is usually measured in pixels. Physical printed height depends on pixel density.

Viewport Height

Viewport height determines the vertical size of a rendered region. It can be expressed in pixels or logical units.

Height Map

A height map stores one height value over each horizontal location, commonly used for terrain and surface displacement.

Terrain Height

Rendering engines convert height-map values into elevations to build landscapes. Scale factors convert stored numbers into world units.

Height in Computer Vision

Vision estimates object height from calibrated images, stereo, depth sensors or known references.

Pixel Height

Object pixel height changes with distance and perspective. Without camera calibration or known scale, it does not directly reveal physical height.

Height from Perspective

Known camera geometry and ground-plane assumptions can convert image height into approximate real height.

Person Height Estimation

Computer vision can estimate human height, but pose, footwear, camera angle and occlusion create uncertainty.

Height in Robotics

Robots use height for obstacle clearance, shelf levels, tool positions and navigation in 3D environments.

End-Effector Height

A robot tool’s height is its vertical coordinate in a chosen frame. Full pose also requires horizontal position and orientation.

Obstacle Height

Mobile robots need obstacle height to decide whether to cross, avoid or pass beneath objects.

Height in Drones

Drones use altitude and relative height for flight control, mapping and obstacle avoidance.

Height in GIS

GIS represents elevation and feature height for buildings, trees, terrain and 3D city models.

Building Height in GIS

Building height may come from lidar, photogrammetry, planning records or extrusion assumptions. Data source affects accuracy.

Digital Surface Model

A digital surface model represents elevations of terrain plus objects such as buildings and trees.

Digital Terrain Model

A digital terrain model aims to represent bare-earth elevation. Subtracting terrain from surface models estimates object heights.

Height in Remote 3D Models

Point clouds and meshes encode vertical coordinates. Coordinate reference system and vertical datum must be preserved.

Height in Data Visualisation

Bar charts often encode value using height. Humans compare aligned heights accurately, making bars effective for quantitative comparison.

Bar Height

Bar height should start from a meaningful baseline, usually zero for ordinary magnitude comparisons. Truncated axes can exaggerate differences.

Height in Statistics

Height can be an observed variable with a population distribution. Means, percentiles and standard deviations describe groups, not individual value judgments.

Height Distribution

Human height distributions are approximately bell-shaped in many populations but vary with age, sex, ancestry, nutrition and cohort.

Height Percentile

A height percentile gives relative position within an appropriate reference population, not a universal ranking of health or value.

Height in Machine Learning

Height can be a feature, target or spatial dimension. Models need units and scaling to use it appropriately.

Height as a Feature

Including height in a model can improve prediction when relevant but can also serve as a proxy for demographic or biological characteristics, requiring careful fairness assessment.

Height in Artificial Intelligence

AI systems use height in spatial reasoning, vision, robotics and 3D reconstruction. The measurement must be tied to a frame and scale rather than inferred from image appearance alone.

Height and Bounding Boxes

An object’s bounding-box height is the vertical span of its box, not necessarily its true physical height or shape.

Height in Networks

Network diagrams may use vertical position to encode hierarchy or layer, but that height is symbolic rather than physical.

Height in Organisations

Organisational “height” can describe number of hierarchical layers. Tall organisations have more management levels under this metaphor.

Height in Trees and Data Structures

Tree height in computer science is the maximum number of edges or nodes from root to a leaf, depending on convention.

Binary Tree Height

Balanced binary trees keep height logarithmic relative to node count, supporting efficient search and update operations.

Graphical Tree Height

Rendered tree height is distinct from structural tree height; layout scale can change without changing data structure.

Height in Probability

A probability density curve has vertical height representing density, not probability itself. Probability is area under the curve over an interval.

Density Height

A density value can exceed one if the horizontal unit is small enough; the total integral must equal one.

Height in Signals

Signal amplitude is sometimes shown as graph height relative to a baseline. The vertical plot scale can represent voltage, pressure, displacement or another quantity.

Wave Height

Wave height physically measures crest-to-trough vertical distance, while graph amplitude is usually half peak-to-peak height for a symmetric wave.

Height and Pressure

Fluid pressure at a point depends on depth below the free surface rather than container shape under static uniform-density conditions.

Height and Potential Energy

Vertical height difference contributes to gravitational potential-energy change. Choice of zero reference is arbitrary for potential differences near Earth.

Height and Stability

A higher centre of mass can reduce resistance to tipping for the same support base. Height therefore matters in vehicles, furniture and structures.

Centre-of-Mass Height

Centre-of-mass height is not the same as total object height. It depends on how mass is distributed vertically.

Height and Moment

Tall structures create longer lever arms for lateral loads, increasing overturning moments at the base.

Height and Wind Exposure

Wind profiles and turbulence change with height above ground. Tall structures need height-dependent wind analysis.

Height and Fire Safety

Building height affects evacuation, firefighting access and smoke movement. Regulatory definitions vary by jurisdiction and occupancy.

Height and Accessibility

Counter, shelf, control and handrail heights influence accessibility. Designs should account for a range of body sizes and mobility needs.

Height and Privacy

Precise building, person or asset heights can sometimes reveal identity or site characteristics when combined with other spatial data.

Height and Fairness

Systems that infer height from images can perform unevenly across body types, clothing, poses and camera conditions. Evaluation should reflect intended users and environments.

Height and Measurement Error

Vertical measurement error arises from instrument calibration, posture, surface unevenness, refraction, coordinate datum and endpoint definition.

Height and Precision

Reporting height to more decimal places than the method supports creates false precision. A laser scan and a visual estimate justify different digits.

Height and Resolution

Pixel, lidar or encoder resolution sets a lower bound on detectable height change, but noise and calibration can make effective accuracy worse.

Height and Temperature

Structures and instruments expand thermally, changing measured heights slightly. High-precision metrology controls or corrects temperature.

Height and Settlement

Building or ground settlement changes elevations over time. Repeated height surveys reveal vertical movement.

Height Monitoring

Survey markers, GNSS, levelling and sensors track changes in structural or terrain height. Stable reference points are essential.

Common Misconceptions About Height

Height is not always total length, altitude, elevation or depth. A slanted object’s length can exceed its height, a building can have several regulatory heights and GNSS height is not automatically mean-sea-level elevation.

A Practical Height Checklist

Define the base, top point, vertical direction, datum, units and whether the measurement is perpendicular, geodetic or local. For buildings and people, follow a stated protocol. For images, calibrate scale before converting pixels to physical height.

How to Measure Height Reliably

Use direct measurement when practical, or triangulation, levelling, lidar or photogrammetry when the object is inaccessible. Control posture, instrument level, reference surface and environmental effects, then record uncertainty.

How to Compare Heights

Use the same vertical reference, units, measurement protocol and time. Do not compare ellipsoidal GNSS height directly with orthometric elevation or standing height with recumbent length without appropriate conversion and context.

Frequently Asked Questions About Height

What is height in simple terms? Vertical distance from a base or reference to an upper point. Is height the same as altitude? Not always. Why must geometric height be perpendicular? Because height measures shortest separation from a base line or plane.

Authoritative Starting Points

Geometry defines perpendicular height in areas and volumes; surveying and geodesy define elevations and datums; physics uses height in energy and fluids; architecture and engineering control clearances and structure; biology and medicine standardise stature; GIS and vision estimate heights from spatial data. Across fields, height is vertical separation made explicit.

What Is Height? The Complete Idea

Height is a directional length tied to a vertical reference. It can describe a triangle, person, building, mountain, aircraft, fluid column or data structure. Strong height reasoning always names the base, vertical direction, datum, units and measurement method, because “how high?” is incomplete without “above what?”