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What is LiDAR Data


LiDAR basics: Huge numbers of densely‐spaced discrete pulses of light (signals) are sent towards a surface from an aerial or, more recently, ground‐based, platform. Sensors measure the return time (travel time over the speed of light = distance, or elevation) and other qualities, of all signals reflected back to the platform. The data is delivered in LAS format files. Millions of highly accurate data points can be produced in just a few city blocks.


About This Data


Westchester County acquired LiDAR data, developed in 2009 through a cooperative project of NYC DEP, NYS CSCIC, and the USGS. The County received the raw LAS data (ASPRS LAS v1.1) and a 3‐m terrain dataset (UTM, Zone 18N, meters; Horizontal Datum NAD 83, Vertical Datum NAVD 88), and converted the 3‐meter‐resolution digital elevation model to NY State Plane East, U.S. survey feet. Through a contract, the County will also obtain new products from the LAS data, including updated 2‐foot elevation contours, and the first countywide digital surface model (DSM).
These data were specified at accuracies required for updating FEMA flood maps. Collected between April 16 and June 25, 2009, with some re‐flights on November 29 and December 2, at a nominal 1‐meter point spacing, and a vertical accuracy of 18.5 centimeters root mean square error (RMSE) or better.



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White Plains, New York 10601