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2003 Puget Sound LiDAR Consortium (PSLC) Topographic LiDAR: Snohomish County, Washington

browse graphicThis kmz file shows the extent of coverage for the 2003 PSLC Snohomish County, WA lidar data set.
TerraPoint surveyed and created this data for the Puget Sound LiDAR Consortium under contract. The area surveyed is approximately 167 square miles and covers a northwest portion of Snohomish County, WA. All data was collected during ideal conditions (leaf-off). The LAS files were derived from all returns ASCII files contain the X,Y,Z values of all the LiDAR returns collected during the survey mission. The GPS time, classification, scan angle, intensity and return numbers of each point were preserved in the conversion from ASCII to LAS. The LAS files are classified into the following ASPRS classes: (1) Unclassified (2) Bare Earth. Ground and water points are included in Class 2 (Bare Earth). Futher details are available in the Process Steps below. The NOAA Coastal Services Center noticed that some intensity values are 0, so be aware before using the intensity information. This dataset was flown in 2003 with a 50% overlap between flight lines. Due to the overlap the nominal point spacing of the dataset is 1.0 meter.

Cite this dataset when used as a source.

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    Distribution Formats
    • LAZ
    Distributor Distributor information not available
    Point of Contact Diana Martinez
    Puget Sound Lidar Consortium (PSLC)
    206-971-3052
    dmartinez@psrc.org
    Documentation links not available.
    Originator
    • Diana Martinez
      Puget Sound Lidar Consortium (PSLC)
    Publisher
      Date(s)
      • publication: 2013-03-01
      Data Presentation Form: Digital image
      Dataset Progress Status Complete
      Data Update Frequency: As needed
      Purpose: 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. This high accuracy data can be used at scales up to 1:12000 (1 inch = 1,000 feet). 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.
      Time Period: 2003-04-02  to  2003-04-12
      Spatial Reference System:
      Spatial Bounding Box Coordinates:
      N: 48.300496
      S: 48.025012
      E: -122.175578
      W: -122.409833
      Spatial Coverage Map:
      Themes
      • Topography/Bathymetry
      • Elevation
      • Model
      • LiDAR
      • LAS
      • Remote Sensing
      Places
      • US
      • Puget Sound
      • Washington
      • Snohomish County
      Use Constraints No constraint information available
      Fees Fee information not available.
      Lineage Statement Lineage statement not available.
      Processing Steps
      • Acquisition. Lidar data were collected in leaf-off conditions (approximately 1 November - 1 April) from a fixed-wing aircraft flying at a nominal height of 1,000 meters above ground surface. Aircraft position was monitored by differential GPS, using a ground station tied into the local geodetic framework. Aircraft orientation was monitored by an inertial measurement unit. Scan angle and distance to target were measured with a scanning laser rangefinder. Scanning was via a rotating 12-facet pyramidal mirror; the laser was pulsed at 30+ KHz, and for most missions the laser was defocussed to illuminate a 0.9m-diameter spot on the ground. The rangefinder recorded up to 4 returns per pulse. Flying height and airspeed were chosen to result in on-ground pulse spacing of about 1.5 m in the along-swath and across-swath directions. Most areas were covered by two swaths, resulting in a nominal pulse density of about 1 per square meter.
      • Processing. GPS, IMU, and rangefinder data were processed to obtain XYZ coordinates of surveyed points. For data acquired after January 2003 (NW Snohomish, Mt Rainier, Darrington, and central Pierce projects), survey data from areas of swath overlap were analysed to obtain best-fit in-situ calibration parameters that minimize misfit between overlapping swaths. This reduces vertical inconsistency between overlapping swaths by about one-half. Heights were translated from ellipsoidal to orthometric (NAVD88) datums via GEOID99
      • ASCII file generation All Point returns with all their attributes were directly exported into ASCII files. These were first divided into USGS quarter quads (3.25 minute by 3.25 minute) and then in 25 tiles per quarter quad.
      • The NOAA Coastal Services Center (CSC) received topographic files in ASCII .TXT format. The files contained lidar elevation measurements. The data were received in Washington State Plane North Zone 4601, NAD83 coordinates and were vertically referenced to NAVD88 using the Geoid99 model. The vertical units of the data were feet. CSC performed the following processing for data storage and Digital Coast provisioning purposes: 1. The ASCII .TXT files were parsed and converted to LAS version 1.2 using LAStools' txt2las tool. 2. Bad elevations were filtered and removed from many tiles across the data set on a tile by tile basis using LASTools' las2las tool. 3. The topographic las files were converted from orthometric (NAVD88) heights to ellipsoidal heights using Geoid99. 4. The topographic las files were converted from a Projected Coordinate System (WA SP North) to a Geographic Coordinate system (NAD 83). 5. The topographic las files' vertical units were converted from feet to meters. 6. The topographic las files' horizontal units were converted from feet to decimal degrees. 7. 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: 2013-04-25

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