Construct · 3 fields · 3 citations

isochrone: one construct, many systems

One name. One construct. Different systems. One map.

● invariant · the line of equal elapsed time, across systems Nearest construct by meaning·not indexed
isochrone3 SYSTEMSIsochrone (age)VANDENBERG · STELLAR AGEIsochrone (runoff)SAGHAFIAN · RUNOFF TIMEIsochrone (reach)FU · TRAVEL-TIME CONTOUR

Spokes are the systems the one construct recurs in; dashed arcs are shared lineage. Tap a field for its definition, unit, and measures.

2002Isochrone (runoff)2015Isochrone (age)2022Isochrone (reach)
2026

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Astronomy

Locus in the H-R / color-magnitude diagram of coeval stars of one age.

In stellar astrophysics an isochrone is the curve in a theoretical Hertzsprung-Russell (or color-magnitude) diagram occupied by a population of stars sharing a single age and composition; fitting it to a cluster yields that cluster's age, as in VandenBerg, Stetson and Brown's work on the Carina dwarf. The 'equal time' here is time since formation, i.e. age. The same Greek root (isos + chronos) names the equal-travel-time contours of hydrology and transport, the recurring idea being a line of constant time-value in different systems.[1]

Unit
One isochrone, measured in Gyr (the age it represents).
Recovery means
Overlay model loci of fixed age on a cluster's color-magnitude diagram.
Measured by
Fit stellar-evolution model grids to cluster photometry.

Hydrology

Contour joining points with equal travel time of runoff to the outlet.

In catchment hydrology an isochrone joins all points from which surface runoff takes the same time to reach the basin outlet; the family of isochrones (the time-area diagram) drives hydrograph routing, as in Saghafian, Julien and Rajaie's time-variable isochrone method. The 'equal time' is runoff travel time. It is the same equal-time-contour idea as the transport isochrone, and the stellar age locus applies that idea to age.[2]

Unit
One isochrone, measured by its travel-time value (hours).
Recovery means
Delineate equal-flow-time bands across a watershed.
Measured by
Flow-path routing over a digital elevation model; time-area analysis.

Transport Geography

Contour bounding locations reachable within a given travel time (accessibility).

In transport geography and planning an isochrone bounds the area reachable from a point within a fixed travel time, the standard primitive of accessibility analysis, as in Fu and colleagues' study of space-time accessibility in transit networks. The 'equal time' is journey time through a network. It is the same equal-time-contour idea as the hydrologic isochrone, and the stellar isochrone applies that idea to age.[3]

Unit
One isochrone, measured by its time budget (minutes).
Recovery means
Compute the reachable set for a time threshold on a transport network.
Measured by
Shortest-path / routing over a transport graph in GIS.

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Nearby constructs

accessibility2 fields · 2 citationsjingle · one word, two carriersbasin1 fields · 1 citationsanchor · a standalone constructbeing3 fields · 3 citationsjingle · one word, three constructs

References

  1. VandenBerg, D. A., Stetson, P. B., & Brown, T. M. (2015). Color-magnitude diagram constraints on the metallicities, ages, and star formation history of the stellar populations in the Carina dwarf spheroidal galaxy. The Astrophysical Journal, 805(2), 103. https://doi.org/10.1088/0004-637X/805/2/103
  2. Saghafian, B., Julien, P. Y., & Rajaie, H. (2002). Runoff hydrograph simulation based on time variable isochrone technique. Journal of Hydrology, 261(1-4), 193-203. https://doi.org/10.1016/S0022-1694(02)00007-0
  3. Fu, X., Zuo, Y., Zhang, S., & Liu, Z. (2022). Measuring joint space-time accessibility in transit network under travel time uncertainty. Transport Policy, 116, 355-368. https://doi.org/10.1016/j.tranpol.2021.12.018

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