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2008 USDA Forest Service Lidar: Sandy River Study Area

browse graphicThis kmz file shows the extent of coverage for the 2008 USDA Forest Service Sandy River Study Area lidar data set..
Watershed Sciences, Inc. collected Light Detection and Ranging (LiDAR) data for the Sandy River study area in collaboration with the USDA Forest Service. The areas for LiDAR collection have been designed as part of a collaborative effort of state, federal, and local agencies in order to meet a wide range of project goals. This LiDAR data set was collected Sept 29 - Oct 1, 2008 and falls mainly in Multnomah County, but also in small portions of Clark and Clackamas Counties, Oregon. This data set consists of bare earth and unclassified points. The average pulse density is 8.04 pulses per square meter over terrestrial surfaces. The area of interest (AOI) encompasses approximately 34,021 acres and the total area flown (TAF) covers 35,873 acres. The TAF acreage is greater than the original AOI acreage due to buffering and flight planning optimization. In some areas of heavy vegetation or forest cover, there may be relatively few ground points in the LiDAR data. Elevation values for open water surfaces are not valid elevation values because few lidar points are returned from water surfaces. Lidar intensity values were also collected.

Cite this dataset when used as a source.

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    Distribution Formats
    • LAZ
    Distributor DOC/NOAA/NOS/CSC > Coastal Services Center, National Ocean Service, National Oceanic and Atmospheric Administration, U.S. Department of Commerce
    Point of Contact Ian Madin
    DOGAMI
    971-673-1542
    ian.madin@dogami.state.or.us
    Documentation links not available.
    Originator
    • DOC/NOAA/NOS/CSC > Coastal Services Center, National Ocean Service, National Oceanic and Atmospheric Administration, U.S. Department of Commerce
    Originator
    • USDA Forest Service
    Publisher
    • DOC/NOAA/NOS/CSC > Coastal Services Center, National Ocean Service, National Oceanic and Atmospheric Administration, U.S. Department of Commerce
    Date(s)
    • publication: 2012-01-01
    Data Presentation Form: Digital image
    Dataset Progress Status Complete
    Data Update Frequency: Not planned
    Purpose: Provide high resolution terrain elevation and land cover elevation data.
    Use Limitations
    • These data depict the elevations at the time of the survey and are only accurate for that time. 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. Any conclusions drawn from analysis of this information are not the responsibility of NOAA or any of its partners. These data are NOT to be used for navigational purposes.
    Time Period: 2008-09-29  to  2008-10-01
    Spatial Reference System: urn:ogc:def:crs:EPSG::4269 Ellipsoid in Meters
    Spatial Bounding Box Coordinates:
    N: 45.575607
    S: 45.369807
    E: -122.104372
    W: -122.427072
    Spatial Coverage Map:
    Themes
    • Bathymetry/Topography
    • LiDAR
    • Light Detection and Ranging
    • DEM
    • Digital Terrain Model
    • DOGAMI
    • Elevation data
    • Bare earth
    • High-resolution
    • Bare ground
    • DTM
    Places
    • United States
    • Oregon
    • Pacific Northwest
    • Multnomah County
    • Clark County
    • Clackamas County
    Use Constraints No constraint information available
    Fees Fee information not available.
    Lineage Statement Lineage statement not available.
    Processor
    • Watershed Sciences, Inc.
    • DOC/NOAA/NOS/CSC > Coastal Services Center, National Ocean Service, National Oceanic and Atmospheric Administration, U.S. Department of Commerce
    • DOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department of Commerce
    Processing Steps
    • No metadata was provided to NOAA CSC with this data set. The following process step is derived from the Watershed Sciences, Inc. lidar report. This report may be accessed at: ftp://ftp.csc.noaa.gov/pub/crs/beachmap/qa_docs/or/sandy/sandy_report.doc Acquisition 1. The lidar data were collected between Sept 29 - Oct 1, 2008. 2. The survey used a Leica ALS50 Phase II sensor. 3. Near nadir scan angles were used to increase penetration of vegetation to ground surfaces. 4. Ground level GPS and aircraft IMU were collected during the flight. Processing 1. Laser point coordinates were computed using the REALM software based on independent data from the LiDAR system (pulse time, scan angle), and aircraft trajectory data (SBET). Laser point returns (first through fourth) were assigned an associated (x, y, z) coordinate along with unique intensity values (0-255). The data were output into large LAS v. 1.1 files; each point maintains the corresponding scan angle, return number (echo), intensity, and x, y, z (easting, northing, and elevation) information. 2. These initial laser point files were too large for subsequent processing. To facilitate laser point processing, bins (polygons) were created to divide the dataset into manageable sizes (less than 500 MB). Flightlines and LiDAR data were then reviewed to ensure complete coverage of the study area and positional accuracy of the laser points. 3. Laser point data were imported into processing bins in TerraScan, and manual calibration was performed to assess the system offsets for pitch, roll, heading and scale (mirror flex). Using a geometric relationship developed by Watershed Sciences, each of these offsets was resolved and corrected if necessary. 4. LiDAR points were then filtered for noise, pits (artificial low points) and birds (true birds as well as erroneously high points) by screening for absolute elevation limits, isolated points and height above ground. Each bin was then manually inspected for remaining pits and birds and spurious points were removed. In a bin containing approximately 7.5 - 9.0 million points, an average of 50 - 100 points are typically found to be artificially low or high. Common sources of non-terrestrial returns are clouds, birds, vapor, haze, decks, brush piles, etc. 5. Internal calibration was refined using TerraMatch. Points from overlapping lines were tested for internal consistency and final adjustments were made for system misalignments (i.e., pitch, roll, heading offsets and scale). Automated sensor attitude and scale corrections yielded 3-5 cm improvements in the relative accuracy. Once system misalignments were corrected, vertical GPS drift was then resolved and removed per flight line, yielding a slight improvement (less than 1 cm) in relative accuracy. 6. The TerraScan software suite is designed specifically for classifying near-ground points (Soininen, 2004). The processing sequence began by removing all points that were not near the earth based on geometric constraints used to evaluate multi-return points. The resulting bare earth (ground) model was visually inspected and additional ground point modeling was performed in site-specific areas to improve ground detail. This manual editing of grounds often occurs in areas with known ground modeling deficiencies, such as: bedrock outcrops, cliffs, deeply incised stream banks, and dense vegetation. In some cases, automated ground point classification erroneously included known vegetation (i.e., understory, low/dense shrubs, etc.). These points were manually reclassified as non-grounds. Ground surface rasters were developed from triangulated irregular networks (TINs) of ground points.
    • The NOAA Coastal Services Center (CSC) received the files in las format. The files contained LiDAR elevation and intensity measurements. The data were in UTM Zone 10 NAD83(CORS96) projection, NAVD88 (Geoid03) vertical datum and units were in meters. CSC performed the following processing for data storage and Digital Coast provisioning purposes: 1. The data were converted from UTM Zone 10 coordinates to geographic coordinates. 2. The data were converted from NAVD88 (orthometric) heights to GRS80 (ellipsoid) heights using Geoid03. 3. The data were sorted by time 4. The data were converted to LAZ format.
    • The NOAA National Geophysical Data Center (NGDC) received lidar data files via ftp transfer from the NOAA Coastal Services Center. The data are currently being served via NOAA CSC Digital Coast at http://www.csc.noaa.gov/digitalcoast/. The data can be used to re-populate the system. The data are archived in LAS or LAZ format. The LAS format is an industry standard for LiDAR data developed by the American Society of Photogrammetry and Remote Sensing (ASPRS); LAZ is a loseless compressed version of LAS developed by Martin Isenburg (http://www.laszip.org/). The data are exclusively in geographic coordinates (either NAD83 or ITRF94). The data are referenced vertically to the ellipsoid (either GRS80 or ITRF94), allowing for the ability to apply the most up to date geoid model when transforming to orthometric heights.

    Metadata Last Modified: 2013-02-20

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