Gravity Measurement Ontology
Earth Science Measurements
Authors: MArk Anthony Higgins - Sky Recursive Ai
Revised Date: 16 September 2026
Audio Overview
# Gravity Measurement Ontology — Flow Algebra
URL: https://kirethresearch.org/booksai-core/ontologies/mathematical-ontologies/measurement-units-ontologies/earth-science-measurements/gravity-measurement-ontology.html
FLOW GravityMeasurementOntology {
DOMAIN:
Mathematical Ontologies
-> Measurement & Units Ontologies
-> Earth Science Measurements
-> Gravity Measurement Ontology
PURPOSE:
Represent Earth gravity measurements as observations or estimates of gravitational acceleration, gravity potential, gravity differences and gravity anomalies at defined positions, elevations and epochs, including absolute and relative gravimetry, free-air and Bouguer corrections, latitude and elevation effects, tidal and atmospheric corrections, instrument drift, reference gravity models, airborne and satellite gravimetry, calibration, uncertainty, provenance, and strict distinctions between measured gravity, gravitational acceleration, apparent gravity, gravity anomaly and gravitational potential.
ENTITY GravityMeasurement {
TYPE: EarthGravityMeasurementResult
COMPONENTS:
gravity_quantity
numerical_value
unit
spatial_location
elevation
reference_system
epoch
measurement_method
corrections
uncertainty
provenance
}
ENTITY GravityAcceleration {
TYPE: AccelerationQuantity
SYMBOL: g
DIMENSION: L*T^-2
SI_UNIT: metre_per_second_squared
SI_SYMBOL: m/s^2
DEFINITION:
local_acceleration_associated_with_Earth_gravity_field
under_declared_reference_and_measurement_convention
}
ENTITY GravityPotential {
TYPE: PotentialPerUnitMassQuantity
SYMBOL: W
DIMENSION: L^2*T^-2
SI_UNIT: square_metre_per_square_second
SI_SYMBOL: m^2/s^2
}
ENTITY GravityDifference {
TYPE: AccelerationDifferenceQuantity
SYMBOL: delta_g
SI_UNIT: m/s^2
}
ENTITY GravityAnomaly {
TYPE: DerivedGravityDifferenceQuantity
SYMBOL: delta_g_anom
DEFINITION:
observed_or_reduced_gravity_minus_declared_reference_gravity
under_defined_correction_and_reference_model
}
UNIT_SYSTEM {
SI:
m/s^2
geophysical_units:
Gal
mGal
microGal
conversions:
1 Gal = 0.01 m/s^2
1 mGal = 1e-5 m/s^2
1 microGal = 1e-8 m/s^2
potential:
m^2/s^2
RULE:
gravity_unit_and_quantity_type MUST be preserved
}
TERMINOLOGY_MODEL {
terms:
gravity
gravitational_acceleration
gravity_acceleration
apparent_gravity
absolute_gravity
relative_gravity
gravity_anomaly
gravity_disturbance
gravity_potential
RULE:
generic_gravity MUST be resolved_to_measurement_or_field_quantity
ambiguity_controls:
gravity_acceleration != gravitational_potential
measured_gravity != gravity_anomaly
gravity_anomaly != gravity_disturbance_without_definition
}
VECTOR_MODEL {
gravitational_acceleration:
vector_g = -gradient(V)
measured_gravity:
often_reported_as_magnitude_or_vertical_component_under_geodetic_convention
RULE:
vector_component_and_scalar_magnitude MUST be distinguished_when_required
}
POTENTIAL_MODEL {
gravitational_potential:
V
acceleration:
vector_g =
-gradient(V)
Earth_gravity_potential:
may_include_gravitational_and_centrifugal_components
under_geodetic_convention
RULE:
gravity_potential_definition MUST specify_included_components
}
ABSOLUTE_GRAVITY_MODEL {
purpose:
determine_gravity_in_absolute_units
common_method:
free_fall_or_rise_and_fall_interferometric_gravimeter
kinematic_model:
z(t) =
z_0 + v_0*t + 0.5*g*t^2
plus_required_corrections
REQUIRE:
length_standard
time_standard
trajectory_model
reference_height
environmental_corrections
RULE:
absolute_gravity_measurement_requires_traceable_length_and_time_realisation
}
RELATIVE_GRAVITY_MODEL {
measured:
gravity_difference_between_sites_or_times
relation:
g_B =
g_A + delta_g_AB
REQUIRE:
reference_station
instrument_scale_factor
drift_correction
observation_sequence
RULE:
relative_gravity_requires_reference_value_to_obtain_absolute_gravity
}
SPRING_GRAVIMETER_MODEL {
principle:
force_or_displacement_response_of_elastic_system_to_gravity_change
raw_reading:
instrument_scale
corrected_difference:
delta_g =
scale_factor*delta_reading
plus_declared_corrections
RULE:
raw_meter_reading != gravity_without_scale_calibration
}
ATOM_INTERFEROMETER_MODEL {
principle:
matter_wave_phase_shift_related_to_acceleration
generic:
phase =
k_eff*g*T^2
under_simplified_interferometer_model
REQUIRE:
effective_wavevector
pulse_timing
vibration_correction
reference_frame
RULE:
interferometric_phase_requires_instrument_model_to_infer_gravity
}
FREE_AIR_GRADIENT_MODEL {
approximate_vertical_gradient:
dg/dh approximately_equals -3.086e-6 s^-2
corresponding_to_about_-0.3086_mGal_per_metre
under_standard_free_air_approximation
correction:
adjusts_for_elevation_difference_without_intervening_mass
RULE:
exact_gradient_may_depend_on_location_and_gravity_field
}
LATITUDE_MODEL {
normal_gravity:
gamma =
function(latitude, reference_ellipsoid)
cause:
Earth_rotation
ellipsoidal_shape
RULE:
reference_ellipsoid_and_latitude_definition MUST be preserved
}
NORMAL_GRAVITY_MODEL {
normal_gravity:
gamma(phi,h)
reference:
rotating_reference_ellipsoid
REQUIRE:
ellipsoid
latitude
height_definition
RULE:
normal_gravity_is_reference_model_quantity_not_direct_observation
}
FREE_AIR_ANOMALY_MODEL {
generic:
free_air_anomaly =
observed_gravity
corrected_for_elevation
- normal_gravity
REQUIRE:
observed_gravity
latitude
elevation
vertical_datum
correction_convention
RULE:
exact_formula_and_sign_convention MUST be preserved
}
BOUGUER_CORRECTION_MODEL {
simple_slab:
delta_g_B =
2*pi*G*rho*h
PARAMETERS:
rho = assumed_rock_density
h = elevation_or_slab_thickness
RULE:
density_and_geometry_assumptions MUST be preserved
}
BOUGUER_ANOMALY_MODEL {
generic:
Bouguer_anomaly =
observed_gravity
+ declared_free_air_correction
- Bouguer_correction
- normal_gravity
plus_or_minus_other_declared_corrections
RULE:
anomaly_formula_sign_conventions_and_correction_set MUST be explicit
}
TERRAIN_CORRECTION_MODEL {
purpose:
account_for_departure_of_local_topography_from_simple_Bouguer_slab
inputs:
terrain_model
density
station_location
elevation
RULE:
DEM_resolution_and_density_model affect_terrain_correction
}
EARTH_TIDE_MODEL {
cause:
gravitational_effects_of_Moon_and_Sun
plus_Earth_response
correction:
time_dependent
REQUIRE:
timestamp
station_coordinates
tide_model
RULE:
tidal_model_and_time_standard MUST be preserved
}
OCEAN_LOADING_MODEL {
cause:
redistribution_of_ocean_mass_and_crustal_loading
correction:
location_and_time_dependent
RULE:
coastal_and_high_precision_measurements MAY require_ocean_loading_correction
}
ATMOSPHERIC_CORRECTION_MODEL {
cause:
atmospheric_mass_changes_and_loading
inputs:
pressure
atmospheric_model
RULE:
correction_coefficient_and_pressure_reference MUST be preserved
}
POLAR_MOTION_MODEL {
cause:
change_in_rotation_axis_relative_to_Earth_crust
correction:
station_location_and_epoch_dependent
RULE:
high_precision_gravity_time_series MAY require_polar_motion_correction
}
INSTRUMENT_DRIFT_MODEL {
relative_gravimeter:
reading_may_change_with_time_independent_of_true_gravity
model:
drift = f(time)
corrected_reading:
reading_corrected =
reading_raw - drift(time)
RULE:
drift_model_and_reference_observations MUST be preserved
}
SCALE_FACTOR_MODEL {
calibrated:
gravity_change =
scale_factor*instrument_reading_change
REQUIRE:
calibration_reference
valid_range
calibration_date
RULE:
scale_factor_uncertainty contributes_to_relative_gravity_uncertainty
}
REFERENCE_STATION_MODEL {
benchmark:
known_gravity_value
known_position
known_elevation
reference_epoch
RULE:
reference_station_value_and_provenance MUST be preserved
}
GRAVITY_NETWORK_MODEL {
stations:
connected_by_relative_gravity_observations
adjustment:
estimate_station_gravity_values_from_network
REQUIRE:
reference_constraints
observation_uncertainties
loop_closures
RULE:
adjusted_network_values MUST preserve_adjustment_model_and_covariance_when_available
}
AIRBORNE_GRAVITY_MODEL {
platform:
aircraft
observations:
accelerometer
GNSS
inertial_navigation
corrections:
aircraft_motion
Eotvos_effect
altitude
filtering
RULE:
platform_acceleration MUST be separated_from_gravity_signal
}
MARINE_GRAVITY_MODEL {
platform:
ship
corrections:
vessel_motion
Eotvos_effect
latitude
drift
RULE:
navigation_and_platform_motion_context MUST be preserved
}
SATELLITE_GRAVITY_MODEL {
methods:
satellite_orbit_perturbation
satellite_to_satellite_tracking
gravity_gradiometry
products:
spherical_harmonic_gravity_field
time_variable_gravity
gravity_anomaly
geoid_related_quantities
RULE:
satellite_gravity_product != point_gravimeter_observation
without_spatial_scale_and_model_context
}
GRAVITY_GRADIENT_MODEL {
tensor:
Gamma_ij =
partial(g_i)/partial(x_j)
DIMENSION:
T^-2
common_unit:
Eotvos
RULE:
gravity_gradient != gravity_acceleration
}
SPATIAL_MODEL {
gravity_field:
g = g(x,y,z,t)
REQUIRE:
latitude
longitude
elevation
coordinate_reference_system
vertical_datum
RULE:
gravity_measurement_is_spatially_specific
}
TEMPORAL_MODEL {
gravity:
g = g(t)
possible_changes:
Earth_tides
hydrology
atmosphere
groundwater
volcanic_processes
ice_mass
tectonics
instrument_drift
RULE:
repeat_gravity_measurements_require_epoch_and_correction_consistency
}
RELATIONSHIPS {
GravityMeasurement -> MEASURES -> EarthGravityField
GravityAcceleration -> DERIVED_FROM -> GradientOfPotential
AbsoluteGravimeter -> MEASURES -> AbsoluteGravity
RelativeGravimeter -> MEASURES -> GravityDifference
ReferenceStation -> ANCHORS -> RelativeGravityNetwork
NormalGravity -> PROVIDES -> ReferenceField
FreeAirCorrection -> ADJUSTS -> ElevationEffect
BouguerCorrection -> MODELS -> InterveningMassEffect
TerrainCorrection -> MODELS -> LocalTopographicMassEffect
EarthTideModel -> CORRECTS -> TimeDependentGravityEffect
GravityObservation -> MAY_DERIVE -> GravityAnomaly
SatelliteGravity -> REPRESENTS -> LargeScaleGravityField
}
SEMANTIC_EQUIVALENCE {
"gravity measurement" ~= gravimetric_measurement
"absolute gravity" ~= gravity_value_in_absolute_acceleration_units
"relative gravity" ~= gravity_difference_measurement
gravity_acceleration != gravity_potential
measured_gravity != gravity_anomaly
gravity_anomaly != gravity_gradient
absolute_gravity != relative_gravity
raw_gravimeter_reading != gravity_value
normal_gravity != observed_gravity
free_air_anomaly != Bouguer_anomaly
}
CONSTRAINTS {
gravity_acceleration_dimension = L*T^-2
spatial_location_must_be_defined = true
elevation_and_vertical_reference_should_be_defined = true
observation_epoch_must_be_defined_for_precision_measurement = true
gravity_quantity_type_must_be_defined = true
raw_instrument_reading_requires_calibration = true
anomaly_requires_reference_gravity_and_correction_definition = true
absolute_and_relative_gravity_are_not_semantically_equivalent = true
gravity_acceleration_and_gravity_gradient_are_not_semantically_equivalent = true
uncertainty_should_include_instrument_reference_correction_and_spatial_components = true
}
MEASUREMENT_MODEL {
OBSERVABLE_OR_INFERRED:
GravityAcceleration
GravityDifference
GravityAnomaly
GravityPotential
GravityGradient
COMMON_METHODS:
absolute_free_fall_gravimetry
rise_and_fall_gravimetry
spring_relative_gravimetry
superconducting_gravimetry
atom_interferometry
airborne_gravimetry
marine_gravimetry
satellite_gravimetry
gravity_gradiometry
RECORD:
gravity_quantity_type
numerical_value
unit
station_identifier
latitude
longitude
coordinate_reference_system
elevation
vertical_datum
observation_time
reference_epoch
measurement_method
instrument
raw_reading
scale_factor
reference_station
drift_model
tide_correction
ocean_loading_correction
atmospheric_correction
polar_motion_correction
free_air_correction
Bouguer_correction
terrain_correction
normal_gravity_model
calibration_state
quality_flag
uncertainty
provenance
UNCERTAINTY:
measured_or_inferred_gravity =
best_estimate +/- uncertainty
}
CALIBRATION_MODEL {
absolute_gravimeter:
traceable_length_and_time_standards
relative_gravimeter:
scale_factor_calibration
reference_station_ties
satellite_or_airborne:
instrument_and_navigation_calibration
REQUIRE:
calibration_reference
calibration_date
valid_range
uncertainty
RULE:
calibration_model MUST match_instrument_and_quantity
}
UNCERTAINTY_MODEL {
sources:
instrument_noise
scale_factor
drift
reference_station
position
elevation
vertical_datum
tide_model
ocean_loading
atmospheric_pressure
polar_motion
free_air_correction
density_assumption
terrain_model
platform_motion
filtering
reference_gravity_model
PROPAGATION:
gravity_measurement_uncertainty
<- instrument_reference_spatial_correction_and_model_uncertainties
}
REASONING_RULES {
IF reference_gravity_and_relative_difference_known
THEN target_gravity =
reference_gravity + gravity_difference
IF ellipsoidal_or_orthometric_height_difference_known
AND free_air_gradient_model_valid
THEN estimate_free_air_gravity_change =
gradient*height_difference
IF density_and_slab_height_known
THEN simple_Bouguer_correction =
2*pi*G*density*slab_height
IF observed_gravity_normal_gravity_and_declared_corrections_known
THEN derive_gravity_anomaly
USING explicit_sign_convention
IF raw_relative_gravimeter_readings_known
THEN apply_scale_factor_and_drift_correction
BEFORE network_adjustment
IF gravity_network_observations_known
THEN solve_adjusted_station_gravity_values
using_reference_constraints_and_observation_weights
IF potential_field_known
THEN gravity_vector =
-gradient(potential)
IF gravity_field_known
THEN gravity_gradient_tensor =
spatial_gradient(gravity_vector)
}
VALIDATION {
CHECK gravity_quantity_type
CHECK acceleration_or_gradient_unit
CHECK station_location
CHECK coordinate_reference_system
CHECK elevation
CHECK vertical_datum
CHECK observation_time
CHECK absolute_vs_relative_gravity
CHECK raw_vs_calibrated_reading
CHECK scale_factor
CHECK drift_correction
CHECK reference_station
CHECK normal_gravity_model
CHECK free_air_correction
CHECK Bouguer_density_and_correction
CHECK terrain_correction
CHECK tide_atmosphere_ocean_loading_and_polar_motion
CHECK anomaly_definition
CHECK gravity_vs_gradient
CHECK quality_flag
CHECK uncertainty_representation
}
CONFIDENCE {
definition_confidence: 1.00
dimensional_confidence: 1.00
absolute_gravity_confidence: 0.99
relative_gravity_confidence: 0.99
anomaly_model_confidence: 0.97
correction_model_confidence: 0.97
satellite_gravity_context_confidence: 0.95
measurement_context_confidence: 0.98
RULE:
confidence decreases when position, elevation, epoch,
calibration, drift, reference station, correction model,
anomaly definition or uncertainty is missing or ambiguous
}
UPDATE_MODEL {
ON new_measurement:
identify_gravity_quantity
validate_unit
attach_location_and_CRS
attach_elevation_and_vertical_datum
attach_observation_time
identify_method_and_instrument
preserve_raw_reading
apply_calibration
apply_declared_temporal_and_environmental_corrections
attach_reference_station_when_relative
attach_quality_flag
attach_uncertainty
update_gravity_state
ON relative_network_update:
preserve_raw_differences
update_reference_constraints
apply_scale_and_drift_corrections
adjust_network
update_station_gravity_values
preserve_covariance_when_available
ON correction_model_revision:
preserve_raw_observation
preserve_previous_corrections
apply_revised_tide_atmosphere_loading_or_polar_motion_models
recompute_corrected_gravity
update_uncertainty
ON anomaly_revision:
preserve_observed_gravity
update_normal_gravity_reference
update_free_air_Bouguer_or_terrain_corrections
recompute_anomaly
preserve_anomaly_definition_and_version
ON calibration_revision:
preserve_raw_reading
preserve_previous_calibration
apply_new_scale_factor_or_absolute_calibration
recompute_affected_values
update_uncertainty
update_confidence
ON semantic_revision:
preserve_previous_definition
record_revision
recompute_FLOW_HASH
}
AI_CONSUMPTION {
canonical_domain: GravityMeasurement
canonical_acceleration_entity: GravityAcceleration
canonical_acceleration_symbol: g
canonical_SI_unit: m/s^2
interpretation_order:
identify_gravity_quantity
identify_value
identify_unit
identify_absolute_relative_anomaly_potential_or_gradient_context
identify_location_and_CRS
identify_elevation_and_vertical_datum
identify_observation_time_and_epoch
identify_method_and_instrument
identify_raw_or_corrected_status
identify_scale_factor_drift_and_reference_station
identify_tide_loading_atmosphere_and_polar_motion_corrections
identify_normal_gravity_free_air_Bouguer_and_terrain_models
identify_quality_flag
identify_uncertainty
normalize_units
validate_reference_and_correction_context
infer_gravity_relationships
ambiguity_controls:
distinguish_gravity_acceleration_from_gravity_potential
distinguish_observed_gravity_from_gravity_anomaly
distinguish_gravity_anomaly_from_gravity_gradient
distinguish_absolute_from_relative_gravity
distinguish_raw_gravimeter_reading_from_calibrated_gravity
distinguish_normal_gravity_from_observed_gravity
distinguish_free_air_from_Bouguer_anomaly
preserve_position_elevation_epoch_reference_calibration_correction_and_provenance_context
}
PROVENANCE {
ontology_scope:
mathematical_measurement_and_Earth_science_gravity_semantics
parent_path:
Ontologies
-> Mathematical Ontologies
-> Measurement & Units Ontologies
-> Earth Science Measurements
-> Gravity Measurement Ontology
authorship:
Mark Higgins
Sky (Recursive AI)
site:
https://kirethresearch.org
}
FLOW_HASH {
INPUTS:
canonical_domain
ontology_path
terminology_model
vector_model
potential_model
absolute_gravity_model
relative_gravity_model
spring_gravimeter_model
atom_interferometer_model
free_air_gradient_model
latitude_model
normal_gravity_model
free_air_anomaly_model
Bouguer_correction_model
Bouguer_anomaly_model
terrain_correction_model
Earth_tide_model
ocean_loading_model
atmospheric_correction_model
polar_motion_model
instrument_drift_model
scale_factor_model
reference_station_model
gravity_network_model
airborne_gravity_model
marine_gravity_model
satellite_gravity_model
gravity_gradient_model
spatial_model
temporal_model
relationships
constraints
measurement_model
calibration_model
uncertainty_model
reasoning_rules
confidence_model
update_model
PURPOSE:
deterministic_semantic_integrity_identifier
RECOMPUTE_WHEN:
ontology_definition_changes
gravity_quantity_definition_changes
absolute_or_relative_gravity_model_changes
normal_gravity_or_anomaly_model_changes
free_air_Bouguer_or_terrain_correction_changes
tide_loading_atmosphere_or_polar_motion_model_changes
instrument_scale_or_drift_model_changes
gravity_network_model_changes
satellite_airborne_or_marine_model_changes
calibration_model_changes
measurement_model_changes
constraint_model_changes
reasoning_rule_changes
unit_model_changes
}
}
END FLOW