I started recently working in a project where I need to start using EPSG codes to identify coordinate systems and their elements.

I saw that a single EPSG code can identify multiple objects. I am interpreting that each object must be from a different type (i.e., no two Datums can have the same EPSG code, but a Datum and a CRS can).

Am I correct with that assumption?

2 Answers 2


OK, thanks to ycartwhelen I found the answer in the section 5.9 of this document. Indeed, the codes are unique for each type. From the document:

In the EPSG Dataset codes are assigned to CRSs, coordinate transformations, and their component entities (datums, projections, etc.).

Within each entity type, every record has a unique code. Whilst EPSG codes are unique within any one entity type, a code value may be used for multiple entities of different types.


The EPSG dataset describes coordinate reference systems (CRS), each of which are inherently affiliated with a datum.

You might find the answers to this question useful, in particular Dan S.'s answer.

This document published by the same organization in charge of EPSG goes into more depth. Specifically you might find sections 4.2 and 5.1 helpful.

  • 1
    EPSG doesn't just define CRS, it defines datums such as WGS84, units of measure such as Arc Minute etc
    – nmtoken
    Commented Jun 19, 2019 at 16:27

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