2008 Kenai Watershed Forum Topographic LiDAR: Kenai Peninsula, Alaska

Create custom data files by choosing data area, product type, map projection, file format, datum, etc.

Simple download of data files. These are in an orthometric vertical datum and differ from the datum described here.

KMZ file showing the footprint of the area covered.

Map of the area described in this metadata.

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.

System Calibration:

Aero-Metric collected data over a previously surveyed area in Palmer, Alaska. Data was collected at the same settings as this project, using two intersecting perpendicular lines. Two GPS ground stations were operating on

site in order to minimize GPS error. The data was classified in each line separately for ground and other common features between lines, such as building roofs. This data was processed in TerraMatch 8.001 (TerraSolid, Ltd.),

to compute corrections for roll, pitch, heading, and mirror scale. These corrections were applied to the initial processing settings (.res file). The data was reprocessed to verify the corrections were applied properly. The

corrected data was then compared to ground surveyed measurements in order to check for any consistent vertical bias. The final step in calibration verified there was minimal vertical noise due to changes in intensity. This

was done by comparing elevations of points on the airport runway, one point on a runway stripe and another adjacent point on the pavement.

Create a smoothed-best estimated trajectory (SBET) of the sensor at a rate of 200 Hz, by integrating the airborne GPS and IMU data The basis of the GPS coordinates were provided to Aero-Metric by DOWL/HKM, and were referenced

to NAD83 (CORS96) with GEOID06 derived orthometric heights. The maximum baseline distance for this area was 23 km, the average base line length was 15 km. The mean GPS positional accuracy for this area was +/- 0.05 meters.

Integrate SBET and raw laser data to produce point cloud data in LAS 1.1 format for each flight line.

Compute the roll, pitch, heading, and mirror scale correction factors for each flight line, then apply corrections to the corresponding flight line.

Automated classification of the bare-earth data from the lidar point cloud using a series of algorithms customized for the types of terrain encountered in the project.

Manual classification of any data which appears to be bare-earth but was not properly classified using the automated methods.

Create point clouds in LAS 1.1 format for all returns.

Data verified using survey control points, located throughout the area.

Metadata updated for Bounding coordinates, Spatial Reference info using FGDC template

The NOAA Office for Coastal Management (OCM) received the topographic files in LAS V1.1 format. The files contained lidar elevation and intensity measurements. The data were received in

Alaska State Plane Zone 4 (FIPS 5004), NAD83 coordinates and were vertically referenced to NAVD88 using the Geoid06 model. The vertical units of the data were feet. OCM performed the following processing for data storage and Digital Coast provisioning purposes:

1. The User_Data field of the LAS files' header was set to a value (0-7) to reflect the LiDAR Data Areas (Area A: 0, Area B: 1, Area C: 2, Area D: 3, Area E: 4, Area F: 6, Area G: 5, Area H: 7)

2. The classification scheme was rearranged. Class 10 (High Noise) was combined into Class 7 (Low Noise). Class 11 (Single Return, not ground) was reclassified as Class 10. Class 13 (1st return of many returns) was reclassfied as Class 14. Class 14 (2nd return of many) was reclassified as Class 15. Class 15 (3rd of many returns) was reclassified as Class 16. Class 16 (Last return of many) was reclassified as Class 17. (see next processing step for further changes)

3. The topographic las files were converted from orthometric (NAVD88) heights to ellipsoidal heights using Geoid06.

4. The topographic las files were converted from a Projected Coordinate System (AK SP Zone 4) to a Geographic Coordinate system (NAD83).

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.

The NOAA Office for Coastal Management simplified the classification scheme because the classes signifying return numbers were replicating information already in the files. Classes 10, 14, 15, 16, and 17 were moved to class 1. The information content is retained in the return numbers while allowing the files to adhere to the LAS 1.1 classification standard.