WGS84 vs NAD83
Two datums that look identical, are often treated as the same, and quietly drift a metre or two apart. Here is when that matters and when it does not.
The short answer
WGS84 is a global datum used by GPS and the wider world. NAD83 is the official datum for North America. When NAD83 was created in the 1980s the two agreed to within a metre, but they are anchored differently, so today they differ by roughly 1 to 2 metres across the continental United States, and that gap slowly grows.
Does it matter? For a web map, a delivery pin or a hiking track, the difference is invisible. For surveying, engineering, construction or legal boundaries, it is significant and you must transform properly rather than assume they are equal.
Side by side
WGS84
- • Global datum, World Geodetic System 1984
- • The native datum of GPS
- • Maintained by the US NGA
- • Tied to a global reference frame (ITRF)
- • Geographic version: EPSG:4326
- • Used worldwide for data exchange
NAD83
- • North American Datum 1983
- • Official datum for US and Canada mapping
- • Maintained by NOAA / NGS
- • Fixed to the North American tectonic plate
- • Geographic version: EPSG:4269
- • Used for US surveys, parcels, engineering
Why two near-identical datums drift apart
The key difference is what each datum is anchored to. WGS84 is tied to a global reference frame that tracks the Earth as a whole. NAD83 is pinned to the North American plate, so it moves with the continent.
North America drifts a few centimetres a year relative to the globe. Over decades that adds up, which is why two datums that started out almost identical now disagree by a metre or two, and why the offset is not the same everywhere.
Realizations matter: both datums have been refined over time. You will see versions like WGS84 (G2139) and NAD83 (2011), or NAD83 (CSRS) in Canada. For precise work the specific realization, and its epoch, changes the numbers.
When the difference matters
Safe to treat as equal
- • Web and mobile maps
- • Address pins and points of interest
- • GPS tracks and routes
- • Most consumer GIS visualisation
Transform properly
- • Land surveying and cadastral data
- • Civil engineering and construction
- • Legal property boundaries
- • Precise asset and utility mapping
A common gotcha
Survey data is off by about a metre
If precise field data does not line up with a basemap, one source is likely NAD83 and the other WGS84. Because the offset is small, it is easy to miss, but for engineering it is the difference between right and wrong. Always confirm the datum of every dataset before overlaying them.
Transform between WGS84 and NAD83
Reproject a whole file between datums and coordinate systems, free and entirely in your browser.
Frequently asked questions
Are WGS84 and NAD83 the same?
They were nearly identical when NAD83 was defined in the 1980s, but they are anchored differently and now differ by roughly 1 to 2 metres in the continental US. They are not officially the same.
Can I use WGS84 and NAD83 interchangeably?
For consumer maps, yes, the difference is too small to see. For surveying, engineering or legal work, no, you should transform between them with the correct datum transformation.
How far apart are WGS84 and NAD83?
About 1 to 2 metres across the continental United States, and the offset varies by location and grows slowly over time as the North American plate moves.
What EPSG code is NAD83?
The geographic version of NAD83 is EPSG:4269. WGS84 geographic is EPSG:4326. Both have many projected variants such as State Plane and UTM zones.