2010 King County (WA) Dept of Natural Resources and Parks Lidar: Cedar River

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This graphic shows the lidar coverage for the King County Cedar River Topographic LiDAR Survey

Date that the source FGDC record was last modified.

Converted from FGDC Content Standards for Digital Geospatial Metadata (version FGDC-STD-001-1998) using 'fgdc_to_inport_xml.pl' script. Contact Tyler Christensen (NOS) for details.

Partial upload of Positional Accuracy fields only.

Partial upload to move data access links to Distribution Info.

Applications and Work Flow Overview:

1.Resolved kinematic corrections for aircraft position data using kinematic

aircraft GPS and static ground GPS data. Software: Waypoint GPS v.8.10, Trimble

Geomatics Office v.1.62

2.Developed a smoothed best estimate of trajectory (SBET) file that blends

post-processed aircraft position with attitude data Sensor head position

and attitude were calculated throughout the survey. The SBET data were

used extensively for laser point processing. Software: IPAS v.1.35

3.Calculated laser point position by associating SBET position to each

laser point return time, scan angle, intensity, etc. Created raw laser

point cloud data for the entire survey in *.las (ASPRS v. 1.2) format.

Software: ALS Post Processing Software v.2.7

4.Imported raw laser points into manageable blocks (less than 500 MB)

to perform manual relative accuracy calibration and filter for pits/birds.

Ground points were then classified for individual flight lines (to be

used for relative accuracy testing and calibration). Software: TerraScan

v.10.009

5.Using ground classified points per each flight line, the relative

accuracy was tested. Automated line-to-line calibrations were then

performed for system attitude parameters (pitch, roll, heading), mirror

flex (scale) and GPS/IMU drift. Calibrations were performed on ground

classified points from paired flight lines. Every flight line was used

for relative accuracy calibration. Software: TerraMatch v.10.006

6.Position and attitude data were imported. Resulting data were

classified as ground and non-ground points. Statistical absolute

accuracy was assessed via direct comparisons of ground classified

points to ground RTK survey data. Data were then converted to

orthometric elevations (NAVD88) by applying a Geoid03 correction.

Ground models were created as a triangulated surface and exported

as ArcInfo ASCII grids at a 1 -meter pixel resolution. Software:

TerraScan v.10.009, ArcMap v. 9.3.1, TerraModeler v.10.004

7.Converted raw images to tif format, calibrating raw image pixels

for gain and exposure settings of each image. Software: Leica

Calibration Post Processing v.1.0.4

8.Calculated photo position and orientation by associating the SBET

position (Step 3) to each image capture time. Software: IPASCO v.1.3

9.Orthorectified calibrated tiffs utilizing photo orientation information

(Step 8) and the LiDAR-derived ground surface (Step 6). Software:

Leica Photogrammetry Suite v.9.2

10.To correct light imbalances between overlapping images, radiometric

global tilting adjustments were applied to the rectified images. Software:

OrthoVista v.4.4.

11.The color corrected images were then mosaicked together for the

survey area and subset into tiles to make the file size more

manageable. Software: OrthoVista v.4.4.

12.Mosaicked tiles were inspected for misalignments introduced

by automatic seam generation. Misalignments were corrected by

manual adjustments to seams. Software: Adobe Photoshop 7.0,

OrthoVista v.4.4.

LiDAR data is processed using the GPS/INS solution. Data is classified to produce:

Class 1: unclassified points

Class 2: ground points

Class 7: low point (noise)

The NOAA Office for Coastal Management (OCM) received the files in las format. The files contained lidar elevation and intensity

measurements. The data were in GA State Plane coordinates and NAVD88 (orthometric) heights in feet. OCM performed the

following processing for data storage and Digital Coast provisioning purposes:

1. The data were converted from WA State Plane North coordinates to geographic coordinates.

2. The data were converted from NAVD88 (orthometric) heights in feet to GRS80 (ellipsoid) heights in meters using Geoid 03.

3. The data were filtered to remove outliers.

4. The LAS data were sorted by latitude and the headers were updated.