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How is access calculated?

The district colours on the map are not based on the question "how many centres are there" but on the **two-step floating catchment area** measure (E2SFCA). This page explains the method in plain terms.

The calculation in three steps

  1. Demand: for each centre, the population of the surrounding districts is summed up weighted by distance. Nearby population counts for more.
  2. Supply ratio: the capacity of the centre is divided by this demand (capacity / demand). Until capacity data is available, every centre counts equally (1).
  3. Access: for a district, the supply ratios of the surrounding centres are summed up weighted by distance. The resulting raw value is scaled to the range 0-100; 100 is the best-served district.

The weight starts at 1 at the centre's location and falls to zero at 60 km. Distances are estimated as straight-line distance × 1.25 (road factor).

What do the colours say?

  • High access: districts whose index lies in the top quartile of scored districts. The threshold is derived from the data anew on every calculation (current highest score: 100.0/100).
  • Medium access: districts that have a score but do not reach the top quartile.
  • No access: districts with known population but no published centre within 60 km — currently 484 districts. This is not a data gap but a finding: there is no access to GETAT in that district. The colour is based on the **number** of centres in the district; an invented score is not recorded.

Currently 488 / 972 districts with a score · last calculation 2026-10-10 · population data 2022 (ADNKS 2022 ilçe nüfusları (06.02.2023 yayımı))

Example calculation

Çeltik (Konya) · population 9,635 · access index none (no published centre within 60 km; the nearest is 140 km away)

For another district: via the search you can open a district and use the "how is access calculated?" link.

What it does not show

  • Not capacity but accessibility is shown: data on doctors, equipment or beds of the centres is not available yet; every centre counts equally.
  • Not the real travel time but an estimate of distance is used; in mountainous provinces the deviation can grow.
  • Not the centre itself but the district is scored. The distribution within a district (town centre–rural) can also vary.
  • A district with a very small population but a centre nearby can receive a high score; population size should also be taken into account when reading the score.

The detailed assumptions of the method are documented in the repository (doc/e2sfca.md). What GETAT is can be read on this page, the values at district level can be seen on the map, and districts can be reached via the search.