Wait—One Transformation Isn’t Enough? Moving Plain NAD83 to NAD83 (2011) and beyond
Skill Level: Beginner, Intermediate, Advanced
Intended Audience: GIS User, GIS Builder, GIS Developer, GIS Instructor, Student, Management
Abstract
For decades, many GIS professionals have treated “NAD83 State Plane” as a sufficiently complete coordinate-system description. When data must be projected, we open the Project tool, select the desired output coordinate system, choose a geographic transformation from the list—wait, choose a geographic transformation?—and click Run. Some users never make that choice at all. Others accept the first or default transformation offered, assuming it must be the best one. But geographic transformations are not interchangeable, and the default may not be the most accurate or appropriate option. The issue becomes even more complicated when moving legacy State Plane data from the original NAD83 datum to NAD83 (2011). That process requires a succession of transformations through the intervening NAD83 realizations: NAD83 (1986) → NAD83 (HARN) → NAD83 (FBN) → NAD83 (NSRS2007) → NAD83 (2011). This requirement surprised several GIS professionals with more than three decades of experience. If seasoned practitioners have not encountered it, how many others are projecting data without realizing that one transformation—or the default transformation—may not be enough? This lightning talk will demonstrate where geographic transformations are selected in ArcGIS Pro and which successive transformations are needed to move Illinois State Plane data from “plain NAD83” to NAD83 (2011) and beyond. As the National Spatial Reference System moves toward modernization, now is the time to examine what “NAD83” really means—and whether our legacy data is ready for what comes next.
Presenter(s)
Peter Schoenfield
Senior GIS Manager, Western Illinois University
Peter Schoenfield has been concerned about addressing since he was an infant (ask him!). In high school, he was the circulation manager for the school newspaper—an early sign of his lifelong obsession with knowing where things belong. Over the past 30+ years, Peter has worked in county government in Illinois with a focus on GIS, specializing in addresses and road centerlines. He served for seven years on the ILGISA NG911 Committee, collaborating with the Office of the Statewide 911 Administrator to support the rollout of Illinois’ NG911 program. Today, he continues that work part-time with the Western Illinois University GIS Center as a Senior GIS Manager, helping communities across the state prepare and maintain compliant NG911 datasets. He holds a Master of Urban Planning with a certificate in GIS from the University of Wisconsin–Milwaukee. Despite decades in the field, he’s still passionate about getting things in the right place—and helping others do the same.