# OSGeo/PROJ

PROJ - Cartographic Projections and Coordinate Transformations Library

Repository: https://github.com/OSGeo/PROJ
Canonical: https://ross.abutalabs.com/products/proj
Homepage: https://proj.org
Language: C++
License: NOASSERTION
License Family: other
Last push: 2026-08-26T10:17:30+00:00

## Health v2 (maintenance only)
Score: 88/100 (v2, computed 2026-09-02T17:46:02.011165+00:00)
- activity 99, release rhythm 66, longevity 100
- inputs: {"age_days": 4121, "days_push": 7, "days_rel": 145, "gap_med": 78.0, "n_releases_24m": 9}
- flags: no_license
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 2007, forks 903 (observed 2026-08-28T04:06:04.782981+00:00)

## What it is
PROJ is a C++ library for generic coordinate transformation, converting coordinates between coordinate reference systems (CRS), including cartographic projections and geodetic transformations. It also ships command-line utilities such as proj, cs2cs, geod, cct, and projinfo for projection and transformation tasks.

## Use cases
- transform coordinates between coordinate reference systems
- project geodetic coordinates to a map projection
- convert lat/lon to UTM
- perform geodesic great circle distance calculations
- look up CRS definitions and coordinate operations
- reproject GIS data to a different datum

## When to choose
- you need accurate, standards-based CRS transformations in C/C++ or via bindings
- you want battle-tested geodetic datum shift and grid-based transformations
- you need CLI tools for quick one-off coordinate conversions

## When to avoid
- you only need simple distance math without CRS handling
- you need a high-level GIS data format reader/writer (use GDAL/OGR instead)
- you cannot manage the proj-data grid resource files required for some datum shifts

## Facets
- artifact type: library
- maturity: stable
- function: geospatial, cli
- domain: developer-tools
- platform: cross-platform, windows, cpp, cli
- tags: coordinate-reference-systems, cartographic-projections, geodetic-transformations, gis, crs, geospatial, maps, linux, macos

## Member repositories
- OSGeo/PROJ (main) score 88

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:06:04.782981+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T03:01:22.231293+00:00, confidence not recorded.
  - readme: https://github.com/OSGeo/PROJ (fetched 2026-08-28T04:06:04.782981+00:00, sha 0c5fb6f8078d)
- Data as of 2026-08-30T08:39:29.467469+00:00.