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Coordinate system and accuracy


Discover's coordinate system

The Discover services' native coordinate system is Web Mercator with a WGS 1984 datum (EPSG 3857). Many users work in coordinate systems with a different datum (for example, EPSG 3566: Utah Central with NAD 1983). Users who need the highest locational precision must use the appropriate geographic transformation to remedy the roughly one meter difference between the WGS84 and NAD83 datums' “realization points.”

UGRC uses the NAD_1983_To_WGS_1984_5 transformation when creating base map tiles and web applications, but there may be more accurate transformations based on the data and area you are working with. The default (no transformation specified) will likely introduce several feet of horizontal positional error. More information about these transformations can be found on ESRI's NAD 1983 To WGS 1984 How-To , opens in a new tab .

Aerial imagery horizontal position accuracy


Google's stated horizontal accuracy is expected to achieve or exceed one meter (CE90) in most areas without significant vertical relief. You can generally expect higher precision in urban areas where existing supplemental ground control was more abundant.


The Hexagon imagery has a stated horizontal accuracy of 1.07 meters (CE90).


The pre-2018 NAIP layers have a stated horizontal positional accuracy of 5 meters, while the 2018 and later NAIP products have a horizontal positional accuracy of 4 meters.