2013 Puget Sound LiDAR Consortium (PSLC) Topographic LiDAR: Tulalip Partnership

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This graphic shows the 2013 lidar coverage for the Tulalip Partnership lidar collection.

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Planning.In preparation for data collection, WSI reviewed the project area using Google Earth,and flightlines were developed using a combination of specialized software. Carefulplanning by acquisition staff entailed adapting the pulse rate, flight altitude, scanangle, and ground speed to ensure complete coverage of the study area at thetarget point density of 11.43 points per square meter (ground points only were calculated at0.83 points per square meter). Efforts are taken to optimize flight paths by minimizingflight times while meeting all accuracy specifications.Factors such as satellite constellation availability and weather windows mustbe considered during the planning stage. Any weather hazards or conditions affectingthe flight were continuously monitored due to their potential impact on the dailysuccess of airborne and ground operations. In addition, a variety of logisticalconsiderations required review including private property access, potential airspace restrictions, and availability of company resources (both staff andequipment).Special care was taken to acquire the tidal flats at low tide wherepossible.

LiDAR Processing Steps:1. Resolve kinematic corrections for aircraft position data using kinematic aircraft GPSand static ground GPS data.Software - Waypoint GPS v.8.3 Trimble Business Center v.3.00 Geographic Calculator 20132. Develop a smoothed best estimate of trajectory (SBET) file that blends post-processedaircraft position with attitude data. Sensor head position and attitude are calculatedthroughout the survey. The SBET data are used extensively for laser point processing.Software - IPAS TC v.3.13. Calculate laser point position by associating SBET position to each laser point returntime, scan angle, intensity, etc. Create raw laser point cloud data for the entire surveyin *.las (ASPRS v. 1.2) format. Data are converted to orthometric elevations (NAVD88) byapplying a Geoid12 correction.Software - ALS Post Processing Software v.2.744. Import raw laser points into manageable blocks (less than 500 MB) to perform manualrelative accuracy calibration and filter erroneous points. Ground points are thenclassified for individual flight lines (to be used for relative accuracy testingand calibration).Software - TerraScan v.13.0085. Using ground classified points per each flight line, the relative accuracy is tested.Automated line-to-line calibrations are then performed for system attitude parameters(pitch, roll, heading), mirror flex (scale) and GPS/IMU drift.Calibrations are calculated on ground classified points from paired flight lines andresults are applied to all points in a flight line. Every flight line is used forrelative accuracy calibration.Software - TerraMatch v.13.0026. Classify resulting data to ground and other client designated ASPRSclassifications (Table 7). Assess statistical absolute accuracy via direct comparisonsof ground classified points to ground RTK survey data.Software - TerraScan v.13.008 TerraModeler v.13.0027. Generate bare earth models as triangulated surfaces. Highest hit models were createdas a surface expression of all classified points (excluding the noise and withheldclasses). All surface models were exported as ESRI grids at a 3-foot pixel resolution.Software - TerraScan v.13.008 ArcMap v. 10.1 TerraModeler v.13.002

The NOAA Office for Coastal Management (OCM) downloaded topographic files in LAZ format from PSLC's website.The files contained lidar easting, northing, elevation, intensity, return number, class, scan angleand GPS time measurements. Entiat data were received in Washington State Plane North, 4601 (feet) andreferenced to NAVD88 (feet).OCM performed the following processing for data storage and Digital Coast provisioning purposes:1. The All-Return LAZ files were cleared of variable lengths records.2. The All-Return LAZ files were converted from a Projected Coordinate System (State Plane 4601)to a Geographic Coordinate system (NAD83).3. The All-Return LAZ files were converted from NAVD88 to ellipsoidal heights using Geoid03.