2012 Puget Sound LiDAR Consortium (PSLC) Topographic LiDAR: Quinault River Watershed, Washington (Delivery 1)

Watershed Sciences, Inc. (WSI) collected Light Detection and Ranging (LiDAR) data on the Quinault watershed survey area for the Puget Sound LiDAR Consortium. This data set covers approximately 181 square miles. Due to spring snow on the ground WSI was unable to acquire data for the complete survey during the initial flights in April and will return to finish acquisition at a later date. Delivery 1 of the survey area was collected on March 24th and 25th and April 8th and 9th and 22nd.

The LiDAR survey utilized both a Leica ALS60 and a Leica ALS50-II sensor in a Cessna Caravan 208B.All areas were surveyed with an opposing flight line side-lap of =60% (=100% overlap) to reduce laser shadowing and increase

surface laser painting. The Leica laser systems allow up to four range measurements (returns) per pulse, and all discernible laser returns were processed for the output dataset.

This LiDAR survey achieved a nominal point spacing of 9.23 points per square meter.

The LAS files can be used to create DEMs and also to extract topographic data in software that does not support raster data. Other surface features can also be extracted with custom applications. LiDAR data has a wide range of

uses such as earthquake hazard studies, hydrologic modeling, forestry, coastal engineering, roadway and pipeline engineering, flood plain mapping, wetland studies, geologic studies and a variety of analytical and cartographic

projects.

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A footprint of this data set may be viewed in Google Earth at:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/2508/supplemental/wa2012_pslc_quinault_footprint.KMZ

A LiDAR Report from the vendor for this data set may be viewed here:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/2508/supplemental/wa2012_pslc_quinault_lidarreport.pdf

LiDAR points in LAZ format

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Any conclusions drawn from the analysis of this information are not the responsibility

of Watershed Sciences Inc., PSLC, NOAA, the Office for Coastal Management or its partners.

This data can be obtained on-line at the following URL:

https://coast.noaa.gov/dataviewer/#/lidar/search/where:ID=2508

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Users should be aware that temporal changes may have occurred since this data set was collected

and some parts of this data may no longer represent actual surface conditions. Users should not use

this data for critical applications without a full awareness of its limitations. These data

depict the heights at the time of the survey and are only accurate for that time.

Elevations are recorded in floating-point meters and the vertical datum is ellipsoidal (GEOID03). There are no other attribute tables.

Not applicable for pure elevation data: every XY error has an associated Z error.

Relative accuracy refers to the internal consistency of the data set - the ability to place a laser point in the same location over multiple flight lines, GPS conditions, and aircraft attitudes. Affected by system attitude

offsets, scale, and GPS/IMU drift, internal consistency is measured as the divergence between points from different flight lines within an overlapping area. Several Relative Accuracy Calibration Methods were used including

Manual System Calibration, Automated Attitude Calibration, and Automated Z Calibration. A detailed explanation of each is provided in the LiDAR Report listed above.

Absolute accuracy is largely a function of laser noise and relative accuracy. To minimize these contributions to absolute error, a number of noise filtering and calibration procedures were performed prior to

evaluating absolute accuracy. The LiDAR quality assurance process uses the data from the real-time kinematic (RTK) ground survey conducted in the AOI. For the Quinault River watershed survey area a total of 1,212 GPS measurements

were collected on hard surfaces distributed among multiple flight swaths. To assess absolute accuracy the location coordinates of these known RTK ground points were compared to those calculated for the closest ground-classified

laser points. A detailed explanation of steps takes to increase Absolute Accuracy are provided in the LiDAR Report listed above.

The root mean square error (RMSE) for vertical accuracy is provided. These statistics assume the error distributions for x, y, and z are normally distributed, thus we also consider the skew and kurtosis of distributions when

evaluating error statistics. Statements of statistical accuracy apply to fixed terrestrial surfaces only and may not be applied to areas of dense vegetation or steep terrain.

; Quantitative Value: 0.026 meters, Test that produced the value: Root mean square Z error in open, near-horizontal areas, as specified by contract. Units in meters. Accuracy may be significantly less in steep areas and under heavy forest canopy.

Elevation data has been collected for all areas inside project boundaries. The data set was flown with a 60% sidelap between flightlines and a 100 meter buffer to ensure all areas are properly sampled.

Puget Sound LiDAR Consortium evaluates logical consistency of high-resolution liDAR elevation data with three tests: examination of file names, file formats, and mean and extreme values within each file; internal consistency of

measured Z values in areas where survey swaths overlap; and visual inspection of shaded-relief images calculated from bare-earth models.

File names, formats, and values: All file naming convention and file formats are checked for consistency.

Visual inspection of bare earth surfaces were examined to find any obvious data errors such as blunders, border artifacts, gaps between data quads, no-data gaps between flight lines, hillscarps, land shifting due to GPS time errors, etc.