2005 Puget Sound LiDAR Consortium (PSLC) Topographic LiDAR: Lower Columbia River

Terrapoint, on behalf of multiple agencies, collected topographic lidar of the Lower Columbia River area. Field data collection took place between the dates of January 10th and February 20th, 2005. The control network

and checkpoint surveys were performed from January 4th to February 12th, 2005. The project area covers approximately 890 square miles along the Columbia River, from the Bonneville Dam to the Pacific Ocean.

A total of 431 flightlines were required to cover the project area flightlines.

Terrapoint used a 40 kHz Airborne Laser Terrain Mapping System ALTMS sensor attached to a Navajo Twin-engin aircraft (C-FVZM). The mission was flown at 3500 feet above ground level at an average speed of 140 knots. The system

consists of a 36 degree full scan angle laser, a Trimble 4700 GPS receiver and a Honeywell H764 IMU unit. The nominal flightline spacing was 1070 feet with 30 to 50% sidelap.

The surveyed and processed data was received divided by funding agency. The agency responsible for funding each tile is represented as a number (0:COE, 1:DNR, 2:DOGAMI, 3:DOI) in the "User Data" field of each LAS file.

The purpose of this project was to provide a high quality DEM of the site for multiple participating agencies.

10791

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

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/2535/supplemental/wa2005_pslc_lowercolariver_geo_footprint.KMZ

A project report for this project from the vendor may be obtained at:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/2535/supplemental/wa2005_pslc_lowercolariver_projectreport.pdf

LiDAR points in LAS 1.2 format (ASPRS Classes 1,2,6,7)

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

of Terrapoint, PSLC, NASA, DOI, COE, DOGAMI, DNR, 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=2535

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be aware that temporal changes may have occurred since this data set was collected and some parts of this data may no longer represent actual surface conditions.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

See Vertical Accuracy Report below.

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

The GPS and inertial data were processed in tandem to achieve the best positional result. Once the position and attitude of the aircraft were known at each epoch (1-second intervals), then

these data were integrated with the laser ranges to provide a position for each data point on the ground. The data were then processed using the proprietary laser processing software suite to produce

coordinates. Each flight involved setting up two base stations to collect data. Utilizing two base stations ensures GPS data collection in the event that the main base station fails. For all flights

the GPS data were of high quality. This minimized the absolute error for the aircraft position.

To verify that the accuracy criteria were being achieved, 10,092 kinematic checkpoints were compared with a triangulated surface generated from the bald earth LiDAR points.

; Quantitative Value: 0.25 meters, Test that produced the value:

AccuracyZ at the 95% confidence level (2 sigma) for soft/vegetated surface in flat or rolling terrain. 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.

Once the data setup has taken place the manual quality control of the surface occurs. This process consists of visually examining the LiDAR points within Terrascan and correcting errors that

occurred during the automated process. These corrections include verifying that all non ground elements, such as vegetation and buildings are removed from the ground model and that all small

terrain undulations such as road beds, dykes, rock cuts and hill tops are present within the model. This process is done with the help of hillshades, contours, profiles and crosssections.

To correct misclassifications, a full suite of Terrascan and custom inhouse data tools are used.