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
- Demand: for each centre, the population of the surrounding districts is summed up weighted by distance. Nearby population counts for more.
- Supply ratio: the capacity of the centre is divided by this demand (capacity / demand). Until capacity data is available, every centre counts equally (1).
- 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 2026-10-09 · population data 2022 (ADNKS 2022 ilçe nüfusları (06.02.2023 yayımı))
Example calculation
Kocasinan (Kayseri) · population 404,780 · access index 17.2/100
| Centre | District | Distance | Weight |
|---|---|---|---|
| Kayseri Şehir Hastanesi GETAT Merkezi | Melikgazi, Kayseri | 3.1 km | 0.949 |
| Erciyes Üniversitesi GETAT Merkezi | Melikgazi, Kayseri | 3.1 km | 0.949 |
| Erciyes Üniversitesi Sağlık Uygulama ve Araştırma Merkezi | Melikgazi, Kayseri | 3.1 km | 0.949 |
| T.C. Sağlık Bakanlığı Kayseri Şehir Hastanesi | Melikgazi, Kayseri | 3.1 km | 0.949 |
Weight = 1 − (distance ÷ 60 km). The further away a centre is, the smaller its contribution; at 60 km it becomes zero. There is no other centre within the threshold around this district.
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.