Data,  Tips and Tricks

Coordinate Systems Supported by RIGIS

The standard coordinate system used by RIGIS is Rhode Island State Plane NAD83 U.S. Survey Feet (EPSG 3438). Nearly all datasets distributed by RIGIS use this coordinate system, and this is the coordinate system we use behind the scenes to manage and archive these data.

However when RIGIS migrated its data clearinghouse to the Esri ArcGIS Hub, we began supporting a second coordinate system for our vector datasets: WGS84 (EPSG 4326). By introducing support for this coordinate system, vector datasets distributed by RIGIS are now easily used by software such as Google Earth Pro.

How do you know what coordinate system is used by the dataset you’ve downloaded from RIGIS?

  • If you downloaded the vector dataset using the “Full Dataset” or “Filtered Dataset” download option, then it uses the WGS84 coordinate system.
  • If you downloaded the vector dataset using the link to the source RIGIS dataset listed under the “Additional Resources” download option, then it most likely uses Rhode Island State Plane NAD83 U.S. Survey Feet.
  • Ultimately you should always review the metadata. All data distributed by RIGIS is delivered with documentation – or metadata – that includes a description of its coordinate system.

Technical background note: RIGIS does not permit downloading data using the Rhode Island State Plane NAD83 U.S. Survey Feet coordinate system using the “Full Dataset” or “Filtered Dataset” download options. There are two reasons for this:

  • Offering data with the WGS84 coordinate system opens up RIGIS data to a much broader audience. Many free GIS data viewers simply do not support RI State Plane, or do not support projecting from RI State Plane to other coordinate systems.
  • The Esri technical support staff we’ve interacted with to date have not known what datum transformation is used behind the scenes to convert between these two coordinate systems.

What about the upcoming NGS release of the new geometric reference frame and geopotential datum in 2022? RIGIS has followed NGS recommendations by maintaining thoroughly documented metadata records whenever possible. We occasionally monitor the development of transformation tools and will certainly consider migrating data distributed by RIGIS to the new reference frame in the future.