distance
Let an agent state distances with their path, unit, method and uncertainty, and never mix straight-line, route and travel-time distances.
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 state distances with their path, unit, method and uncertainty, and never mix straight-line, route and travel-time distances.
The amount of space between two points, objects or places, measured along a specified path or as the straight-line length, in units of length.
What it is for: Measuring separation, for navigation, planning, engineering and science.
It can be measure it, by survey, GNSS, laser or odometer; compute it, from coordinates or a network; convert it between units; use it, for routing, pricing and planning.
Distinguishing features
A length, with a path: straight line, great circle, along a route
Distinct from displacement, which has direction
Distinct from travel time, which depends on speed
Always needs a unit and ideally a method
What it looks like
Not a thing to look at; seen on maps, signs and instruments as a number with a unit.
Physical character
unit: metre (SI) m - mile 1609.344 m, nautical mile 1852 m
How it is recognised
A number with a length unit: m, km, mi, nmi, ft
Road signs and maps state route or straight-line distances
Track gauge, a distance between rails, is one specialised distance
Related models
is a kind of - a physical quantity measured in metres
is confused with - displacement is a vector
is used in - routes, fares and plans depend on it
has specialisation - the distance between rails
In practice
Families and kinds
Euclidean, great-circle, geodesic, route or network distance
specialised distances such as track gauge and wheelbase
abstract distances in mathematics, such as metric distances
Identifiers
SI unit metre, symbol m base unit of length
Standards and regulation
International System of Units (SI)
ISO 80000-3 space and time quantities
WGS 84 for geodetic distances
Failure modes and hazards
Unit confusion, such as miles for kilometres or feet for metres
Mixing straight-line and route distances
Projection errors when measuring on flat maps
Also called
+55
Where this came from
wikidata · CC0 1.0
Also registered as vr.tr.distance-time
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 4 bundles · 8 layers · 8 findings · 16 questions.
Definition and path What distance is meant.
A distance is meaningless without the path it follows.
Path
Straight line, great circle or route.
Path type
The path along which distance is taken.
- Along which path is this distance measured? definition
- How different is it from the straight-line distance? measurement
Endpoints
The two points.
Endpoint definition
The points and their coordinates.
- Between which two points exactly? definition
- How precisely are those points located? measurement
Measurement How it was obtained.
Method determines accuracy.
Method
Survey, GNSS, odometer, calculation.
Measurement method
The method and instrument.
- How was this distance measured or computed? provenance
- What is its uncertainty? measurement
Reference system
Datum and projection.
Reference frame
The datum and projection used.
- Which datum and projection were used? provenance
- How much distortion does the projection introduce? measurement
Units Units and conversion.
Unit errors have caused real accidents.
Unit
The unit stated.
Unit stated
The unit and its definition.
- In which unit is this distance given? definition
- Could the unit be misread? boundary
Conversion
Converting units.
Conversion factors
Exact conversion factors.
- Which exact factor converts this unit to metres? measurement
- What rounding was applied? measurement
Use Distances in decisions.
Distances drive fares, routes and safety margins.
Application
Where the distance is used.
Use context
The decision the distance feeds.
- What decision does this distance feed? definition
- Would a travel time be more appropriate? boundary
Safety margins
Distances as limits.
Margin rules
Required minimum distances.
- Is a minimum distance required here, and by which rule? provenance
- How is compliance measured? measurement
What the second pass must settle
- Should route distance and straight-line distance be separate entries?
- How should uncertainty in measured distances be recorded?
- Should specialised distances such as track gauge be children of this entry?