2006 USGS North Puget Sound LIDAR survey

Ralph Haugerud
U.S. Geological Survey
c/o University of Washington
Seattle, WA
31 March   2008
rhaugerud@usgs.gov

Overview of survey

In 2006 the U.S. Geological Survey contracted for a lidar survey of most of western Whatcom and Skagit counties, Washington, including the area bordering the Skagit River as far east as Ross Dam.  The resulting data are presented here. Note that these are not Puget Sound Lidar Consortium data. The data were acquired to different specifications by a different contractor. 

The survey was designed in accordance with FEMA lidar data collection standards to provide on-ground pulse spacings of no greater than 1.4 meters, or approximately 0.5 pulse/m2. The task order for this survey specified horizontal accuracy of 1 m or better (RMSE), vertical accuracy of 18.5 cm RMSE (37 cm in vegetated areas), and return classification adequate to remove 95% of all outliers, 95% of all vegetation, and 98% of all buildings. Data were acquired in May, June, August, and September 2006, using Leica ALS-50 and Optech 2050 instruments. Data quality is discussed further here.

These data are in the public domain and there are no legal restrictions on their use. If you choose to note the source of the data, please credit the United States Geological Survey. The USGS does not warrant that these data are fit for any use. You are responsible for verifying that these data are fit for the uses you put them to. Please see Data quality.

Acknowledgements--Vivian Queija and H. Lee Case (USGS) coordinated and arranged for funding of the North Puget Sound survey, with support from Terry Curtis (Washington Department of Natural Resources) and Josh Greenberg (Skagit County). Data were acquired by The Sanborn Map Company under a specific limited offer to the USGS for reduced-cost lidar data. The acquisition contract was written and managed by the National Geospatial Technical Operations Center (NGTOC) of the USGS. Ralph Haugerud (USGS) rewrote ASCII XYZ files and built DEMs and images from the point lists delivered by Sanborn.

Data layers and downloads

Two data layers were delivered: all-return point lists in LAS 1.1-format files, with each file covering an area 3,000 ft x 3,000 ft, and ASCII-format XYZIR files (X,Y,Z, intensity, and return number) of ground points, tiled according to the same scheme.

The LAS files are presented here as delivered. All have been checked for readability. ASCII XYZ data and bare-earth DEMs presented here were constructed from the delivered XYZIR files. Highest-hit DEMs were constructed from the data in the LAS files.

All data are in Washington State Plane projection, North zone, horizontal datum NAD83, units U.S. Survey Feet. The vertical datum is NAVD88, Geoid03, units feet.

LAS files  lists of files

As delivered by the contractor. LAS 1.1 format, point record format 1. See Documentation for a spatial index to these tiles. Note that no files were delivered for tiles PS5494, PS5495, PS5496, and PS5497. 6,135 files.

ASCII XYZ files of ground points  lists of files

Comma-delimited, X (easting) Y (northing) Z (elevation) data, one point per line. Zip-compressed. For the most part, derived from the XYZ-intensity-return# files delivered by the contractor. Retiled to 3,000-ft square tiles with boundaries at even values of State Plane easting and northing and named by easting and northing, e.g., file x1584y642.xyz.zip has its southwestern corner at 1,584,000 feet easting and 642,000 feet northing. See Documentation for a spatial index to these tiles. 6,514 files.

Bare-earth DEMs  list of files

6-ft XY resolution floating-point Z rasters constructed from retiled XYZ ground points. A triangulated irregular network (TIN) was constructed from ground points, then sampled to a raster via the ArcInfo TINLATTICE command with LINEAR interpolation. The resulting raster was clipped at the data-area boundary to avoid interpolation artifacts at re-entrants in the survey boundary. See Data quality for discussion of known artifacts.

Gzip-compressed ArcInfo export (.e00) files. Each file corresponds to approximately 1/4 of a standard USGS 7.5-minute quadrangle. Data in file is for minimum bounding rectangle for quarter-quadrangle, thus file areas overlap slightly. The naming scheme is described in qq_scheme.pdf. 224 files.

Highest-hit DEMs  list of files

6-ft XY resolution floating-point Z rasters constructed from 1st returns as identified in the LAS files. 1st returns were isolated and sorted into 6 ft x 6 ft cells. Highest-hit DEM elevation is the the elevation of the highest 1st return in each cell. Cells with no 1st returns have value NODATA. See Data quality for discussion of known artifacts.

Gzip-compressed ArcInfo export (.e00) files. Each file corresponds to approximately 1/4 of a standard USGS 7.5-minute quadrangle. Data in file is for minimum bounding rectangle for quarter-quadrangle, thus file areas overlap slightly. The naming scheme is described in qq_scheme.pdf. 224 files.

Bare-earth images  list of files    Highest-hit images  list of files

6-ft XY resolution JPEG images of the bare-earth and highest-hit surface models. Images calculated with illumination from NE at 45 degrees above the horizon. NODATA areas are white. There is some degradation because of image compression. Users who need the utmost possible detail should calculate their own images from the appropriate DEM.

Each image corresponds to approximately 1/4 of a standard USGS 7.5-minute quadrangle. Images overlap slightly. The naming scheme is described in qq_scheme.pdf. For use in a GIS, be sure to download the world (.jgw) file associated with each image. 448 files for bare-earth images, 448 files for highest-hit images.

Mosaic of bare-earth filegeodatabase

Indexes to all data files, by quadrangle

Documentation

Task Order (contract specifications)    .pdf file
Report of Survey     .doc file     .pdf file
Discussion of data quality
Index to contractor's tiling scheme (for PSxxxx files)    zipped shape file    zipped .e00 file
Index to retiled data (xEEEEyNNN files)    zipped shape file    zipped .e00 file
Outline of delivered data     zipped shape file    zipped .e00 file
Quarter-quadrangle naming scheme  .pdf file