Internally, the workers that compute advanced data (ET0, frost, AQI) operate on a City entity — a map point with a stable identifier. When you create a Field, the system needs to associate it with a City so those workers can run for your Field.
How the association works
When you create the Field, the backend searches:
- Is there an existing City in the database within 5 km of the Field's coordinates? If yes, associate that one. Done.
- If nothing is found within 5 km, create a new satellite City with the Field's name + "(field)" suffix, the Field's coordinates, and associate it to the correct country
Why 5 km?
An empirically chosen radius:
- Within 5 km — weather data (temperature, rainfall, wind) is practically identical. Associating to an existing City is efficient because we already have historical data and running workers for it
- Beyond 5 km — meaningful differences can exist (microclimate, orographic shadows). Better to create a dedicated City
Does this affect me?
Almost never. The anchor City is completely transparent to you:
- The Field name in the selector is the one YOU gave it, not the City name
- The Vigía push says "Frost at Napa Estate", not "Frost at Napa-satellite-3"
- Advanced Data is displayed as the Field's data, not the anchor City's
When would you see it?
Only in two edge cases:
- If you open the city search (Settings → Search city) and see a City with a name like "Napa Estate (field)" — that's a satellite City created for your Field
- If our support team asks for the City ID associated to a Field for debugging purposes
Do satellite Cities accumulate?
No. When you delete a Field:
- If the anchor City had other associations (other users' Fields, or historical data references), it's kept
- If it was a satellite City exclusive to the deleted Field, it becomes orphaned — a periodic backend sweep re-links it to the nearest City or archives it
What if I edit a Field and change its coordinates?
The search re-runs: if the new coordinates are within 5 km of an existing City, it re-anchors to that one. If not, it keeps the previous City (changing the anchor City would break the historical record). If the Field moved significantly, it's better to create a new Field at the new location — so it starts fresh.