EPSG.io: Discover coordinate systems worldwide

EPSG.io is developed and run with ♥ by MapTiler, a company providing maps for developers, map tiling software, data and server for self-hosting, and other tools for building digital maps.

The initial version was developed in cooperation with the Moravian Library in Brno. The main developers are Petr Pridal, Tomas Pohanka, Ali Ashraf, Radim Kacer, and the rest of the MapTiler team, but also many other people from the community around EPSG.io. 

Yes, EPSG.io is free to use for searching, viewing, and downloading coordinate reference system (CRS) details. There are no hidden charges for these features. 

Bulk data transformation, API access, and other advanced features are available through the MapTiler Coordinate API. It has a generous free tier and competitive prices that are affordable for your business.

EPSG.io uses the official EPSG and ESRI databases. MapTiler built a service with a custom interface around it.

The EPSG database, maintained by the IOGP, is updated several times a year. EPSG.io aims to reflect these updates shortly after each new release.

Report an error or issue with EPSG.io via MapTiler support.

A geospatial reference system defines how geographic or geospatial data is accurately represented on maps or GIS platforms. It includes key components such as coordinate systems, datums, and projections, ensuring consistent spatial referencing across datasets.

For example, EPSG codes (like EPSG:4326 for WGS84) standardize these systems, allowing seamless geospatial data integration from different sources.

In short, a spatial reference or geospatial reference provides the framework for positioning, aligning, and analyzing spatial data reliably in mapping and GIS applications.

An EPSG code is a unique identifier for a specific coordinate reference system (CRS), datum, projection, area, or transformation. These codes come from the EPSG Geodetic Parameter Dataset, maintained by the International Association of Oil & Gas Producers (IOGP).

Why is it important?

• Ensures consistency across different software, tools, and platforms.

• Removes ambiguity when defining and sharing coordinate systems.

• Simplifies geospatial workflows by providing a standard reference.

Using EPSG codes guarantees accurate and reliable geospatial data interpretation and integration.

1. Use the search bar: Enter the EPSG code, CRS name, or relevant keywords in the search bar on the homepage.

2. Apply filters: Narrow results by region or projection type if needed.

3. Explore details: Click on the desired result to view detailed information, including transformation parameters and technical specifications.

The EPSG registry is a database maintained by the International Association of Oil & Gas Producers (IOGP). It contains a comprehensive list of coordinate reference systems (CRS), datums, projections, and datum transformations used globally in geospatial applications. The IOGP ensures that the EPSG registry remains authoritative, up-to-date, and consistent across the geospatial community.

Both PROJ and EPSG.io rely on the official EPSG Geodetic Parameter Dataset, but differences can happen due to:

1. Different Transformations and Parameters: The PROJ library and EPSG.io might use different versions or implementations of geodetic transformations. PROJ includes a wide variety of transformation methods, and sometimes, default parameters or transformations can differ slightly depending on the version of PROJ you're using or specific configuration settings.

2. Parameter Updates: Both the EPSG dataset and PROJ are periodically updated with new parameters or corrections. However, it might happen that the EPSG.io is not reflecting the latest available data yet, or your local version of PROJ is based on an older dataset.

3. Specific Settings or Options: Some transformations in PROJ may depend on specific settings or additional parameters that are not always explicitly set in EPSG.io 's interface. If PROJ is set up with custom parameters or transformations not reflected in EPSG.io, it could lead to discrepancies.

To resolve this:

• Check that the databases and software versions match.

• Compare transformation parameters in both tools.

• Verify that the same transformation method is selected.

Neither tool is wrong in most cases—they might just be configured differently.

1. Double-check the spelling or syntax of the code or CRS name.

2. Look for alternative projections or coordinate systems that may be equivalent.

3. If the code or CRS is not in the EPSG registry, consider contacting the official EPSG registry maintained by IOGP and submitting a request for it to be added.

Yes, EPSG.io offers a simple REST API to access:

• Coordinate Reference System (CRS) definitions

• Datum transformations

• Ellipsoid information

• Datum

• Prime meridian 

These can be retrieved in WKT, JSON, PROJ strings, or other formats.

Example API URLs:

• CRS Definition:
  Retrieve the WKT representation of EPSG:5514:
  https://epsg.io/5514.wkt

• CRS with Transformation Parameters:
  Retrieve CRS EPSG:5514 with transformation EPSG:1623 (including TOWGS84 parameters):
  https://epsg.io/5514-1623.wkt

For more advanced geospatial functionality, such as bulk transformations and comprehensive coordinate system searches, consider using the MapTiler Coordinates API, which offers an extended suite of REST API capabilities.

The most used projections include:

• UTM (Universal Transverse Mercator): Used for large-scale maps, dividing the world into 60 zones.

• Mercator: Common for world maps, particularly web maps (e.g., MapTiler Maps).

• Albers Equal Area Conic: Commonly used for mapping areas with a larger east-west extent, like the United States.

• Lambert Conformal Conic: Often used for aeronautical charts.

• WGS84: A geographic coordinate system (GCS); widely used in GPS.

Each projection serves specific purposes based on area, scale, and accuracy requirements. Selecting the right one depends on the needs of your project.

When a projection, coordinate reference system (CRS), or transformation is marked as deprecated, it is no longer recommended for use and may have been replaced by a more accurate or updated version.

What should you do?

• Use alternatives: Look for the recommended replacement projection on EPSG.io.

• Check compatibility: Legacy datasets may still require the deprecated projection, but updating is advised if possible.

• Stay informed: Keep an eye on changes to geospatial standards to ensure you're using supported systems.

Why should I avoid using deprecated projections or datums?

1. Outdated Accuracy: Deprecated systems may not align with modern geospatial standards, leading to errors or distortions in data representation.

2. Compatibility Issues: Modern GIS software and tools might have limited support for deprecated projections, causing integration problems.

3. Future Removal: Deprecated systems are often phased out in updates, risking data loss or functionality issues in the long term.

4. Better Alternatives Exist: Updated projections or datums often offer improved accuracy and regional optimizations.

5. Stability and Support: Actively maintained systems ensure reliable results and ongoing support in geospatial workflows.

Switching to recommended and up-to-date projections ensures accuracy, long-term compatibility, and smoother integration across platforms.

A datum transformation converts geographic coordinates (latitude, longitude) or projected coordinates (e.g., Easting, Northing) from one datum to another. Datums define how we model the Earth's shape and size, and differences between them can cause misalignments in geospatial data.

A datum transformation adjusts the coordinates to account for these differences, ensuring that geospatial data aligns properly across different systems.

How are Datum Transformations Performed?

Datum transformations use a set of parameters (a combination of translation, rotation, and scale factors) to define the relationship between the two datums and allow the conversion from one coordinate system to another. They account for differences in the reference ellipsoids, geoid models, and other defining properties of the datums.

Types of Datum Transformations:

1. 7-Parameter Transformations: The most common methods use translation (shift along X, Y, Z axes), rotation (around the X, Y, Z axes), and scale (change in size) to align the datums.

2. Grid-based Transformations: In specific cases, like for local datums, grid shifts may be used, where a grid of pre-calculated transformation values is applied to each point in the data.

3. Geocentric Transformations: These are used when transforming from one geocentric datum (like WGS84; EPSG:4326) to another.

More information can be found in this YouTube video.

Yes, you can download EPSG data for offline use through the EPSG.io REST API. It lets you retrieve CRS definitions, datum transformations, and ellipsoid information in WKT, JSON, PROJ strings, or other formats.

Using the parameter download=true, you can download, for instance, the following URLs:

• https://epsg.io/5514.wkt?download=true

• https://epsg.io/5514-1623.wkt?download=true

These free and public API endpoints make storing and integrating CRS data locally into geospatial projects or workflows easy.

EPSG.io regularly updates its dataset to align with the official EPSG Geodetic Parameter Dataset maintained by the IOGP.

• Updates are applied periodically to ensure accuracy and alignment with the latest official changes.

• The current version number and release date of the dataset are usually displayed on the EPSG.io homepage.

• While updates might not always be immediate, EPSG.io aims to stay as up-to-date as possible with each new release.

Yes, you can use the information from EPSG.io with GIS software (e.g., QGIS, ArcGIS) or web mapping tools (e.g., Leaflet, OpenLayers). The EPSG code provided by EPSG.io can be directly applied in most GIS tools to define your project's coordinate reference system (CRS).

Selecting the right datum transformation parameters involves a few key steps:

1. Understand your source and target datums

   Identify the source datum (the datum of your original coordinates) and the target datum (the datum you want to convert to). Common examples include WGS84, NAD83, ETRS89, etc.

   Each datum defines the Earth's shape and size differently, and transforming between them typically requires applying specific transformation parameters.

2. Find EPSG codes

   Use EPSG.io to find codes for your datums and related transformations.

3. Use the recommended transformation

   EPSG.io suggests standard, well-tested transformation methods (e.g., using a set of 7-parameter transformations with translation, rotation, and scale factors parameters).

4. Check for region-specific adjustments

   Some areas have localized transformations for better accuracy. Look for regional recommendations if available.

5. Consider accuracy needs

   For high-precision tasks (e.g., surveying), consult authoritative sources or local geospatial agencies.

6. Validate using PROJ or other GIS tools

   Use software like PROJ, QGIS, or ArcGIS to test transformation parameters and verify accuracy.

7. Review documentation and data sources

   Check the authoritative geospatial sources to ensure the transformation parameters are up-to-date and appropriate for your use case.

8. Test with known points

   Compare transformed coordinates with trusted reference datasets to ensure accuracy.

• WGS84 (World Geodetic System 1984; EPSG:4326):

  • Global Datum: Designed for worldwide use.

  • Geocentric Ellipsoid: Based on a model centered on the Earth's mass.

  • Primary Use: GPS systems and global mapping applications.

• NAD83 (North American Datum 1983; EPSG:4269):

  • Regional Datum: Optimized specifically for North America.

  • Ellipsoid Difference: Uses a slightly different reference ellipsoid than WGS84.

  • Primary Use: Surveying, engineering, and mapping in the U.S. and Canada.

While both datums are similar, slight differences in their ellipsoids and reference points can cause positional offsets.

1. Region of Interest:

   • Use a local or regional CRS (e.g., UTM) for small to medium-sized areas.

   • Use a global CRS (e.g., WGS84, EPSG:4326) for global datasets or large-scale maps.

2. Scale and Purpose:

   • For large areas: Use projections like Albers Equal Area to minimize area distortion.

   • For local precision: Use UTM zones for accurate distance and direction measurements.

3. Accuracy Requirements:

   • Choose a CRS that reduces distortion for your specific location and mapping needs.

4. Data Compatibility:

   • Ensure your chosen CRS aligns with your existing or any external datasets you'll integrate.

5. Software Compatibility:

   • Verify that your GIS or mapping tool supports the selected CRS and transformation options.

• Geographic Coordinate System (GCS):

  • Represents locations on a spherical or ellipsoidal model of the Earth.

  • Coordinates are defined using latitude and longitude.

  • Commonly used for global positioning and large-scale measurements.

  • Example: WGS84 (EPSG:4326).

• Projected Coordinate System (PCS):

  • Represents locations on a flat, two-dimensional plane.

  • Coordinates are defined using X (Easting) and Y (Northing) values.

  • Uses a map projection to flatten the Earth's surface for regional or local mapping.

  • Example: UTM (Universal Transverse Mercator); e.g. EPSG:32633.

• Search for the CRS: Enter the EPSG code or name of the target CRS in the search bar on EPSG.io (e.g., EPSG:2056 for Switzerland).

• View Transformation Details: Click on the CRS to see recommended transformation methods and their associated parameters (e.g., translation, rotation, scale).

• Check for Regional Variations: If the default transformation isn’t suitable, look for region-specific transformation methods listed under the CRS details.