1

I have metadata from a Lidar Point Cloud dataset and I'm having trouble understand what exactly was done to it. It reads:

The data (LAS files) were received in UTM Zone 18N NAD83 coordinates (meters) and vertically referenced to NAVD88 using the Geoid 12a model in meters.

This much I understand. It is this part I'm unclear on:

The data files (LAS files) were transformed to geographic (decimal degrees), ellipsoidal coordinates (meters). The transform to ellipsoidal coordinates was done by reversing the application of the GEOID 12a model from a previous step.

Can someone help me out and tell me what this means? Is the vertical spatial reference no longer NAVD88?

I'm trying to create a feature dataset and have no clue what to choose for the vertical coordinate system.

2

The vertical values are now heights above the NAD83 ellipsoid, not gravity-related in any way. So, in ArcGIS, you should assign the NAD 1983 vertical coordinate system.

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