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2008 USGS New Jersey Lidar: Somerset County
browse graphic These data support the general geospatial needs of the USGS and other federal agencies. LiDAR data is remotely sensed high-resolution elevation data collected by an airborne collection platform. By positioning laser range finding with the use of 1 second GPS with 200hz inertial measurement unit corrections, Airborne 1's LiDAR instruments are able to make highly detailed geospatial elevation products of the ground, man-made structures and vegetation. The LiDAR flightlines for this project were planned for a 50% acquisition overlap. The nominal resolution of this project without overlap is 1.203m, with a 0.90m resolution with the 50% overlap, assuming a normal distribution. Two returns were recorded for each pulse in addition to an intensity value. GPS Week Time, Intensity, Flightline and number attributes were recorded for each LiDAR point. Positional values were recorded to the centimeter level, while GPS is recorded to a 10th of a millisecond. Scan angle was recorded to the nearest angle, Intensity is recorded as a 12 Bit dynamic range value and echo is recorded as a numeric value from 0 to 256. The data was originally provided as random points, in LAS v1.1 format, classified according to the following codes: Class 1 Non-ground/Extracted Features Last Pulse Class 2 Bare Earth Ground Features Last Pulse Class 3 Extracted Features First Pulse Class 4 Bare Earth Ground Features First Pulse It should be noted that Class 3 and 4 are not ASPRS classes but since this data is a two pulse system, this is the most efficient format to separate the pulses and classification process. The data was reclassified into 2 distinct classifications: Class 1 Non-ground/Extracted Features First and Last Pulse Class 2 Bare Earth Ground Features First and Last Pulse