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Imposm

Imposm is an importer for OpenStreetMap data. It reads PBF files and imports the data into PostgreSQL/PostGIS. It can also automatically update the database with the latest changes from OSM.

It is designed to create databases that are optimized for rendering (i.e. generating tiles or for WMS services).

Imposm >=3 is written in Go and it is a complete rewrite of the previous Python implementation. Configurations/mappings and cache files are not compatible with Imposm 2, but they share a similar architecture.

The development of Imposm is sponsored by Omniscale.

Imposm is in production use by the authors. It is actively maintained, with a focus on resolving future incompatibilities with dependencies such as PostGIS. However, there is no capacity for end-user support, and no new features will be developed beyond its existing scope.

Features

High-performance
Diff support
Custom database schemas
Generalized geometries

In detail

High performance: Parallel from the ground up. It distributes parsing and processing to all available CPU cores.
Custom database schemas: Creates tables for different data types. This allows easier styling and better performance for rendering in WMS or tile services.
Unify values: For example, the boolean values 1, on, true and yes all become TRUE.
Filter by tags and values: Only import data you are going to render/use.
Efficient nodes cache: It is necessary to store all nodes to build ways and relations. Imposm uses a file-based key-value database to cache this data.
Generalized tables: Automatically creates tables with lower spatial resolutions, perfect for rendering large road networks in low resolutions.
Limit to polygons: Limit imported geometries to polygons from GeoJSON, for city/state/country imports.
Easy deployment: Single binary with only runtime dependencies to common libs (GEOS and LevelDB).
Automatic OSM updates: Includes background service (imposm run) that automatically downloads and imports the latest OSM changes.
Route relations: Import all relation types including routes.
Support for table namespace (PostgreSQL schema)

Performance

Imposm makes full use of all available CPU cores
Imposm uses bulk inserts into PostgreSQL with COPY FROM
Imposm uses efficient intermediate caches for reduced IO load during ways and relations building

An import in diff-mode on a Hetzner AX102 server (AMD Ryzen 9 7950X3D, 256GB RAM and NVMe storage) of a 78GB planet PBF (2024-01-29) with generalized tables and spatial indices, etc. takes around 7:30h. This is for an import that is ready for minutely updates. The non-diff mode is even faster.

It's recommended that the memory size of the server is roughly twice the size of the PBF extract you are importing. For example: You should have 192GB RAM or more for a current (2024) 78GB planet file, 8GB for a 4GB regional extract, etc. Imports with spinning disks will take significantly longer and are not recommended.

Installation

Binary

Binary releases are available at GitHub.

These builds are for x86 64bit Linux and require no further dependencies. Download, untar and start imposm. Binaries are compatible with Debian 10 and other distributions from 2022 or newer. You can build from source if you need to support older distributions.

Source

There are some dependencies:

Compiler

You need Go. 1.17 or higher is recommended.

C/C++ libraries

Other dependencies are libleveldb and libgeos. Imposm was tested with recent versions of these libraries, but you might succeed with older versions. GEOS >=3.2 is recommended, since it became much more robust when handling invalid geometries.

Compile

The quickest way to install Imposm is to call:

go install github.com/omniscale/imposm3/cmd/imposm@latest

This will download, compile and install Imposm to ~/go/bin/imposm. You can change the location by setting the GOBIN environment.

The recommended way for installation is:

git clone https://github.com/omniscale/imposm3.git
cd imposm3
make build

make build will build Imposm into your local path and it will add version information to your binary.

You can also directly use go to build or install imposm with go build ./cmd/imposm. However, this will not set the version information.

Go compiles to static binaries and so Imposm has no runtime dependencies to Go. Just copy the imposm binary to your server for deployment. The C/C++ libraries listed above are still required though.

See also packaging.sh for instructions on how to build binary packages for Linux.

LevelDB

For better performance you should use LevelDB >1.21. You can still build with support for 1.21 with go build -tags="ldbpre121" or LEVELDB_PRE_121=1 make build.

Usage

imposm has multiple subcommands. Use imposm import for basic imports.

For a simple import:

imposm import -connection postgis://user:password@host/database \
    -mapping mapping.json -read /path/to/osm.pbf -write

You need a JSON file with the target database mapping. See example-mapping.json to get an idea what is possible with the mapping.

Imposm creates all new tables inside the import table schema. So you'll have import.osm_roads etc. You can change the tables to the public schema:

imposm import -connection postgis://user:passwd@host/database \
    -mapping mapping.json -deployproduction

You can write some options into a JSON configuration file:

{
    "cachedir": "/var/local/imposm",
    "mapping": "mapping.json",
    "connection": "postgis://user:password@localhost:port/database"
}

To use that config:

imposm import -config config.json [args...]

For more options see:

imposm import -help

Note: TLS/SSL support is disabled by default due to the lack of renegotiation support in Go's TLS implementation. You can re-enable encryption by setting the PGSSLMODE environment variable or the sslmode connection option to require or verify-full, eg: -connect postgis://host/dbname?sslmode=require. You will need to disable renegotiation support on your server to prevent connection errors on larger imports. You can do this by setting ssl_renegotiation_limit to 0 in your PostgreSQL server configuration.

Documentation

The latest documentation can be found here: http://imposm.org/docs/imposm3/latest/

Support

There is a mailing list at Google Groups for all questions. You can subscribe by sending an email to: imposm+subscribe@googlegroups.com

For commercial support contact Omniscale.

Development

The source code is available at: https://github.com/omniscale/imposm3/

You can report any issues at: https://github.com/omniscale/imposm3/issues

License

Imposm is released as open source under the Apache License 2.0. See LICENSE.

All dependencies included as source code are released under a BSD-ish license. See LICENSE.dep.

All dependencies included in binary releases are released under a BSD-ish license except the GEOS package. The GEOS package is released as LGPL3 and is linked dynamically. See LICENSE.bin.

Test

Unit tests

To run all unit tests:

make test-unit

System tests

There are system test that import and update OSM data and verify the database content. You need osmosis to create the test PBF files. There is a Makefile that creates all test files if necessary and then runs the test itself.

make test

Call make test-system to skip the unit tests.

WARNING: It uses your local PostgreSQL database (imposm_test_import, imposm_test_production and imposm_test_backup schema). Change the database with the standard PGDATABASE, PGHOST, etc. environment variables.