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Salta

A small footprint reverse-geocoder for when you don't need precision.

Goal

Salta is a simple reverse geocoder for when you don't need precision, i.e. the most precise location you need is at the city or suburb level.

The aim is to have:

  • low memory usage
  • fast start-up time
  • no database
  • fast updates

Salta relies on the Who's On First database.

Performance

In order to optimize memory usage, on the first launch Salta simplifies polygons and stores a cached version of every processed geojson. On subsequent launches cached files are used when the source hasn't changed.

Country Load time (with cache) Initial load time (no cache) Memory usage Total disk usage (repo/cache)
New Zealand 1s 4mn 23MB 791MB (738MB/53MB)
France 3s 3mn 152MB 4GB (2.9G/914MB)
United States 6s 15mn 259MB 8.6GB (6.8GB/1.8GB)

Loading all place types. Memory usage after GC. SSD drive, AMD Ryzen 3700X.

When using the cache only mode the initial load time can be significantly faster, when loading the whole world is takes:

  • A few seconds to load countries and localities
  • Around five minutes to load all place types

In terms of memory usage for loading the whole world, depending on the place types loaded:

Place type Memory usage
Countries 73MB
Countries + Localities 512MB
Countries + Regions + Localities 818MB
All 1.3GB

The mean response time for HTTP requests is around 200-300μs.

Usage

Config

Sample config file:

# In cache only mode Salta only loads the available cache files. This makes
# start-up significantly faster.
cache_only: true # default: false
countries: # default: all countries
  - nz
  - fr
cache:
  folder: /path/to/salta/cache/folder # default: cache
repos:
  folder: /path/to/salta/repos/folder # default: repos
enabled_place_types: # default: all
  - locality
  - neighbourhood
  - borough
  - microhood
  - county
  - macrocounty
  - localadmin
  - region
  - macroregion
  - country
  - campus
  - marketarea

Supported formats: JSON, YAML.

Run

With Docker

docker run -v $PWD/config.yaml:/config.yaml -t ghcr.io/pixwire/salta:latest

License

Who's on first data requires linking back to their license. See the Who's on first license for more information.

Used by

Salta was created for use in Pixwire.