2014 Puget Sound LiDAR Consortium (PSLC) Topographic LiDAR: Cedar River Watershed (Delivery 1)

In September 2013, WSI, a Quantum Spatial company (QSI), was contracted by the Puget Sound LiDAR Consortium (PSLC) to collect Light Detection and Ranging (LiDAR) data over three areas of interest (AOIs) in the greater Seattle, Washington area. The individual AOIs include the Cedar River Watershed and Floodplain, Lake Youngs Reservoir, and the SCL/Tolt Reservoir, herein all referred to as the Cedar Watershed LiDAR project. This metadata refers to the first delivery of many.

Tiles were delivered as state plane orthometric x,y,z values but have since been reprojected/transformed to geographic, ellipsoidal coordinates for OCM use and storage. Original naming conventions will apply to the FTP available data. The average first-return density of LiDAR data for the Cedar Watershed LiDAR project was 1.15 points per sq. ft (12.41 points per sq m) while the average ground classified density was 0.25 points per sq. ft (2.67 points per sq m)

Data were collected to aid PSLC in assessing the topographic and geophysical properties of the study area.

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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/geoid18/3674/supplemental/wa2014_pslc_cedarriver_delivery1_m3674.kmz

The final report for this project can be viewed at:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/3674/supplemental/wa2014_pslc_cedarriver_delivery1_projectreport_m3674.pdf

LiDAR points in LAZ format (ASPRS Classes 1,2)

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

of Quantum Spatial, 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=3674

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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be aware that temporal changes may have occurred since this data set was collected and some parts of this data may no longer represent actual surface conditions.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.

All discernible laser returns were processed for the output dataset. The discrepancy between native and delivered density will vary depending on terrain, land cover, and the prevalence of water bodies.

When collecting RTK and PPK data, the rover records data while stationary for five seconds, then calculates the pseudorange 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.; Quantitative Value: 0.015 meters, Test that produced the value: 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

The mean and standard deviation (sigma) of divergence of the ground surface model from ground survey point coordinates are also considered during accuracy assessment. These statistics assume the error for x, y and z is normally distributed, and therefore the skew and kurtosis of distributions are also considered when evaluating error statistics. For the Cedar Watershed LiDAR survey, 1,363 ground survey points were collected in total resulting in an average accuracy of -0.28 feet (-0.009 meters). RMSE calculated to be 0.085 ft (0.026 m); Quantitative Value: 0.051 meters, Test that produced the value: FVA (1.96 * RMSE) of 0.167 ft (~5.1 cm), RMSE calculated to be 0.085 ft (0.026 m)

LiDAR data has been collected and processed for all areas within the project study area.

All areas were surveyed with an opposing flight line side-lap of more than 50 percent (more than 100 percent overlap) in order to reduce laser shadowing and increase surface laser painting. To accurately solve for laser point position (geographic coordinates x, y and z), the positional coordinates of the airborne sensor and the attitude of the aircraft were recorded continuously throughout the LiDAR data collection mission. Position of the aircraft was measured twice per second (2 Hz) by an onboard differential GPS unit, and aircraft attitude was measured 200 times per second (200 Hz) as pitch, roll and yaw (heading) from an onboard inertial measurement unit (IMU). To allow for post-processing correction and calibration, aircraft and sensor position and attitude data are indexed by GPS time.