2013-2014 USGS Lidar: Olympic Peninsula (WA)

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This graphic shows the lidar coverage of the Olympic Peninsula area in Jefferson County, Washington.

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This data set is the project specified data extent. | Type of Source Media: vector dataset

This data set is the project specified acquired point cloud data. | Type of Source Media: Lidar dataset

This data set is the project specified lidar deliverables. | Type of Source Media: Lidar dataset

This data set is the project specified acquired ground control and QAQC control data. | Type of Source Media: Control dataset

This data set is the project specified tile index. | Type of Source Media: vector dataset

Using a combination of Leica ALS70 and ALS60 (ALS70/ALS60) systems on board a Pentavia aircraft, high density data, at a nominal pulse spacing (NPS) of 0.35 meters, was collected for this task order (approximately 437 square miles of the Olympic Peninsula in the counties of Jefferson and Clallam in north-western coastal Washington). AGL = 1300/900 meters - Aircraft Speed = variable, Field of View (Full) = 28-30/28 degrees, Pulse Rate = 180-199/95-106 kHz, Scan Rate = 41.7/63.6 Hz, with an average side lap of 50%. Multiple returns were recorded for each laser pulse along with an intensity value for each return. A total of eleven (21) missions were flown between October 13, 2013 and January 25, 2014. The geoid used to reduce satellite derived elevations to orthometric heights was GEOID12A. Data for the task order is referenced to the UTM Zone 10N, North American Datum of 1983 (2011), and NAVD88, in meters. Once the data acquisition and GPS processing phases are complete, the LiDAR data was processed immediately to verify the coverage had no voids. The GPS and IMU data was post processed using differential and Kalman filter algorithms to derive a best estimate of trajectory. The quality of the solution was verified to be consistent with the accuracy requirements of the project. The SBET was used to reduce the LiDAR slant range measurements to a raw reflective surface for each flight line. The coverage was classified to extract a bare earth digital elevation model (DEM) and separate last returns. Field calibration is performed on all flight lines to refine the IMU misalignment angles. IMU misalignment angles are calculated from the relative displacement of features within the overlap region of adjacent (and opposing) flight lines. The raw LiDAR data is reduced using the refined misalignment angles.

Ground control and QAQC control point survey was performed by WSI. This control supported the Olympic Peninsula WA lidar project. Ground survey points (GSP) were collected using real time kinematic (RTK), and post-processed kinematic (PPK) survey techniques. A Trimble R7 base unit was positioned at a nearby monument to broadcast a kinematic correction to a roving Trimble R10 receiver. All GSP measurements were made during periods with a Position Dilution of Precision (PDOP) of less than 3.0 with at least six satellites in view of the stationary and roving receivers. When collecting RTK and PPK data, the rover records data while stationary for five seconds, then calculates the pseudo-range position using at least three one-second epochs. Relative errors for the position must be less than 1.5 cm horizontal and 2.0 cm vertical in order to be accepted. GSP were collected in areas where good satellite visibility was achieved on paved roads and other hard surfaces such as gravel or packed dirt roads. GSP measurements were not taken on highly reflective surfaces such as center line stripes or lane markings on roads due to the increased noise seen in the laser returns over these surfaces. GSP were collected within as many flight lines as possible, however the distribution of GSP depended on ground access constraints and monument locations and may not be equitably distributed throughout the study area. All horizontal GPS control was based on UTM Zone 10N, NAD83 (2011) expressed in meters. The vertical datum used for this project was based on the North American Vertical Datum of 1988 (NAVD88), GEOID12A, also expressed in meters.

The individual flight lines were inspected to ensure the systematic and residual errors have been identified and removed. Then, the flight lines were compared to adjacent flight lines for any mismatches to obtain a homogeneous coverage throughout the project area. The point cloud underwent a classification process to determine bare-earth points and non-ground points utilizing "first and only" as well as "last of many" LiDAR returns. This process determined Default (Class 1), Ground (Class 2), Noise (Class 7), Water (Class 9), and Ignored Ground (Class 10). The bare-earth (Class 2 - Ground) LiDAR points underwent a manual QA/QC step to verify the quality of the DEM as well as a peer-based QC review. This included a review of the DEM surface to remove artifacts and ensure topographic quality. Classification of water (class 9) and ignored ground (class 10) was completed via the use of the hydrologic breaklines collected for the hydro-flattening phase. . The surveyed ground control points are used to make vertical adjustments to the data set and to perform the accuracy checks and statistical analysis of the LiDAR dataset. The hydrologic breakline data was compiled using a combination of lidar intensity data, bare earth surface models, and open source imagery. Compiled hydrologic lines are processed to best represent the water level at the time of the lidar collection. Intensity data is recorded by the lidar sensor and stored in LAS data. The intensity data product was created by isolating the recorded intensity information and generating a gridded raster product from the intensity information.The first return DSM product was created by isolating the first return laser pulses and then creating a gridded raster product derived from the first return data set. The DEM product was created by isolating the ground (class 2) points along with breakline data generated from the hydrologic breakline dataset and generating gridded raster data from this data. Supervisory QC monitoring of work in progress and completed editing ensured consistency of classification character and adherence to project requirements across the entire project area.

Project data extent was provided by USGS and subsequently buffered by 100 meters and provided in shape file format. Project deliverables were clipped to the 100 meter data extent.

Tile Size: 1,000m x 1,000m. The tile file name was derived from the southwest corner of each tile. The tiles are named based on the US National Grid.

The NOAA Office for Coastal Management (OCM) received topographic files in LAS format. The files contained lidar elevation measurements. The data were received in UTM 10N meters, NAD83 coordinates and were vertically referenced to NAVD88 using the Geoid99 model. The vertical units of the data were feet. OCM performed the following processing for data storage and Digital Coast provisioning purposes:

1. LAS files were delivered from USGS via ftp.

2. The files were removed of duplicate and outlier points as well as noise classified points.

3. The LAS files were converted from orthometric (NAVD88) heights to ellipsoidal heights using Geoid12a.

4. The LAS files were converted from UTM coordinates (10N) in meters to a Geographic Coordinate system with decimal degrees units.

5. Names of the LAS tiles were changed slightly to agree with OCM naming conventions, though tiles and points have not be altered.