2015 Oregon Department Forestry Lidar DEM: Northwest OR

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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.

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GeoTerra, Inc. acquired Lidar sensor data with Optech Orion H300 mounted in Cessna 180 on following dates:

- Salmonberry site - April 19th and April 20th 2015

- Wilkerson/Wilark site - May 30th, June 5th and June 6th 2015

- McGregor site - June 6th, June 8th 2015

- Columbia site - June 8th, June 9th 2015

For the Abiqua site, GeoTerra Inc. used the Optech Galaxy Lidar system to acquire the areas. The Optech Galaxy emits higher pulse rate of 35 - 550 kHz and can record up to 8 range measurements per laser pulse emitted. A pulse rate of 450KHz was used and data was collected on March 30, 2016.

Processing.

Relative and absolute adjustment of all strips was accomplished using Optech LMS software and TerraMatch. Optech LMS performs automated extraction of planar surfaces from the cloud of points according to specified parameters per project. Tie plane determination then establishes the correspondence between planes in overlapping flight lines. All plane centers of all lines that form a block are sorted into a grid. Plane surfaces from overlapping flight lines are used, co-located to within an acceptable tolerance, and are then tested for correspondence.

A set of appropriate tie planes is selected for the self-calibration. Selection criteria are size and shape, number of laser points, slope, orientation with respect to flight direction, location within the flight line and fitting error. All these criteria have an effect as they determine the geometry of the adjustment. Self-Calibration parameters are then calculated and used to re-calculate the laser point coordinates (X,Y,Z). The planar surfaces are re-calculated as well for a final adjustment.

Additionally each mission was further reviewed and adjusted in TerraMatch using tie lines approach.

The software measures the difference between lines (observations) in overlapping strips. These observed differences are translated into correction values for the system orientation - easting, northing, elevation, heading, roll, pitch and mirror scale.

Point Classification:

Once the point cloud adjustment was achieved with desired relative accuracy, all strips were exported from Optech LMS into LAS format. Data in LAS format was first automatically classified followed by strict QC procedures. Each site was evaluated for size and was cut into working tiles of a manageable size and manually checked and edited using TerraSolid and LP360.

Following classes were delineated in the process of classification:

- 01_Unclassified (temporary)

- 02_Ground

- 03_Low Vegetation

- 04_Medium Vegetation

- 05_High Vegetation

- 06_Buildings and Associated Structures

- 09_Water - points reflected off water bodies

- 10_Unclassified (Permanent)

DEM creation:

Three-foot floating point Ground and First Return ESRI raster grids were generated using the Lidar points as input to the LAS Dataset to Raster tool and converting an ESRI terrain dataset of the Lidar ground surface into File Geodatabase raster. Class 2 lidar points were used.

The NOAA Office for Coastal Management (OCM) received the files in the proprietary ESRI grid format. The files were converted to floating point GeoTIFF format in vertical meters using gdal_translate from GDAL version 2.1.1.