This piece is a raised-relief terrain map of Long Island at 1:1500000 scale, with 25:1 vertical exaggeration.
Purchase a finished ornament from my Etsy shop at
https://www.etsy.com/listing/489783345/long-island-3d-printed-christmas
The source of the elevation data is the U.S. Geological Survey. The USGS home page is http://www.usgs.gov/.