Difference between WGS84 and EPSG:4326

Question

What is the difference between WGS84 and EPSG 4326?

It seems like for a given dataset it might be both WGS84 and EPSG:4326.

Answer 1

4326 is just the EPSG identifier of WGS84.

WGS84 comprises a standard coordinate frame for the Earth, a datum/reference ellipsoid for raw altitude data.

Answer 2

If you're really going to pick a nit: EPSG 4326 defines a full coordinate reference system, providing spatial meaning to otherwise meaningless pairs of numbers. It means "latitude and longitude coordinates on the WGS84 reference ellipsoid."

The term WGS84 is sometimes used the same way, but also it can refer to the ellipsoid only. For example, you can have "meters northing and easting as measured upon the cylinder formed by projecting the WGS84 ellipsoid using a transverse mercator projection with a central meridian of -123 degrees". (http://spatialreference.org/ref/epsg/32610/)

In any case: No difference, just like everyone else is saying, except in the very nitty gritty details of how they are used.

TLDR: No one says "the EPSG 4326 ellipsoid" as part of a coordinate system definition.

Answer 3

As far as I can see the two are the same thing. Our definition (in FME) is:

Coordinate System Parameters

CS_NAME: LL84
DESC_NM: WGS84 datum, Latitude-Longitude; Degrees
DT_NAME: WGS84
EPSG: 4326
GROUP: LL
MAP_SCL: 1
PROJ: LL
QUAD: 1
SCL_RED: 1
SOURCE: Mentor Software UNIT: DEGREE

Datum Parameters

DESC_NM: World Geodetic System of 1984
ELLIPSOID: WGS84
SOURCE: US Defense Mapping Agency, TR-8350.2-B, December 1987
USE: WGS84

Ellipsoid Parameters

DESC_NM: World Geodetic System of 1984, GEM 10C
E_RAD: 6378137
P_RAD: 6356752.3142
SOURCE: US Defense Mapping Agency, TR-8350.2-B, December 1987

OGC WKT Description GEOGCS["WGS84 datum, Latitude-Longitude; Degrees", DATUM["WGS_1984", SPHEROID["World Geodetic System of 1984, GEM 10C",6378137,298.257223563, AUTHORITY["EPSG","7030"]], AUTHORITY["EPSG","6326"]], PRIMEM["Greenwich",0], UNIT["degree",0.0174532925199433], AUTHORITY["EPSG","4326"]]

ESRI WKT Description GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]]

Answer 4

They are certainly not the same. WGS is a datum(for lat/loong specifations) while EPSG is a database of CRS and related information. Those who think these are same actually ignore the basic purpose of EPSG. The main purpose of EPSG is to assign a code for Geodetic Parameter Dataset that contains a repository of parameters needed to define a CRS. This ensures that coordinates describe position unambiguously.

Answer 5

No they are not equivalent.

WGS is EPSG:7030. As Dan S. has said WGS84 is an ellipsoid (spheroid to be more precise). EPSG:4326 is a geographic coordinate system that makes use of the WGS84 ellipsoid. The difference is more than just nitpicking; however. A geographic coordinate system is more than just the ellipsoid. It adds a coordinate system and units of measurement.

EPSG:4979 is also based on the WGS84 ellipsoid, and differs from EPSG:4326 only in that it uses a 3D coordinate system, whereas 4326 uses a 2D coordinate system. Even geocentric coordinates (e.g. EPSG:4378) are based on an ellipsoid as they don't necessarily have the same centres. In turn, 4326 and 4979 can be built upon by adding a projection and compounding with a vertical datum and coordinate system. They are all WGS84, but it would be wrong to call any of them WGS84 without further qualification.