2011 Puget Sound LiDAR Consortium (PSLC) Topographic LiDAR: Rattlesnake

Watershed Sciences, Inc. (WSI) collected Light Detection and Ranging (LiDAR) data on six days

between September 15th and November 5th, and from November 6th - 13th, 2010 for the Puget

Sound LiDAR Consortium. This report documents the data acquisition, processing methods,

accuracy assessment, and deliverables for the Rattlesnake area of interest in Benton

County, WA. The requested areas were expanded to include a 100m buffer to ensure

complete coverage and adequate point densities around survey area boundaries.

The total acreage of the Rattlesnake AOI is 184,359 acres.

The average first-return density of the delivered dataset is 8.3 points per square meter

for the Rattlesnake study area. The initial datasets, acquired to be =8 points per square

meter, were filtered as described previously to remove spurious or inaccurate points.

Additionally, some types of surfaces (i.e., dense vegetation, breaks in terrain, water,

steep slopes) may return fewer pulses (delivered density) than the laser originally

emitted (native density).

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/geoid18/2587/supplemental/wa2011_pslc_rattlesnake.kmz

A report explaining collection and quality assurance is available at:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/2587/supplemental/wa2011_pslc_rattlesnake.pdf

2011 Kittitas is not directly associated to the data represented in the Rattlesnake area, though

the information in the Kittitas report may be useful to an advanced user for comparative

analysis, it is available at:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/2599/supplemental/wa2011_pslc_kittitas.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 Terrapoint, 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=2587

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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).

Horizontal positional accuracy for LiDAR is dependent upon

the quality of the GPS/INS solution, sensor calibration and ground conditions at the time of

data capture. The standard system results for horizontal accuracy are less than 1 meter.

; Quantitative Value: 1.0 meters, Test that produced the value: Lidar horizontal accuracy was not reported.

To minimize the contributions of laser noise and relative accuracy 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 Rattlesnake study a total 2064

RTK 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.

The vertical accuracy of the LiDAR data is described as the mean and standard deviation

(sigma ~ s) of divergence of LiDAR point coordinates from RTK ground survey point

coordinates. To provide a sense of the model predictive power of the dataset, the root mean

square error (RMSE) for vertical accuracy is also 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.

; Quantitative Value: 0.036 meters, Test that produced the value: Absolute vertical accuracy was calculated to 3.6 cm.

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

LiDAR flight lines have been examined to ensure that there was at least 50% sidelap,

there are no gaps between flightlines, and overlapping flightlines have consistent

elevation values.

Shaded relief images have been visually inspected for data errors such as pits,

border artifacts, gaps, and shifting.