2014 Oregon Department of Geology and Mineral Industries (DOGAMI) Oregon Lidar DEM: Metro Portland, OR

The dataset encompasses 1221.6 square miles in portions of the greater Portland Metro area in the state of Oregon. The highest hit digital surface models (DSM) represent the earth's surface with all vegetation and human-made structures included. The highest hit DSMs were derived from lidar data using TIN processing of the all-return point cloud. The bare earth digital elevation model (DEM) represents the earth's surface with all vegetation and human-made structures removed. The bare earth DEMs were derived from lidar data using TIN processing of the ground point returns. The DSM and DEM grid cell size is 3 feet. The projection was originally Oregon Statewide Lambert Conformal Conic, units are in International Feet. The horizontal datum is NAD 83 (2011) and the vertical datum was NAVD88 (Geoid 12A). Some elevation values have been interpolated across areas in the models where there is no elevation data (e.g. over water, over dense vegetation). Watershed Sciences, Inc. collected the lidar and created this data set for the Oregon Department of Geology and Mineral Industries (DOGAMI). Watershed Sciences, Inc. collected the lidar and created this data set for the Oregon Department of Geology and Mineral Industries (DOGAMI).

Original contact information:

Contact Name: Jacob Edwards

Contact Org: DOGAMI

Phone: 971-673-1557

Email: jacob.edwards@oregon.gov

Provide high resolution terrain elevation data.

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A final report for this project may be viewed at:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid12b/6359/supplemental/OLC_Metro_2014_Survey_Report.pdf

Any conclusions drawn from the analysis of this information are not the responsibility of the Oregon Department of Geology and Mineral Industries (DOGAMI), the Office for Coastal Management or its partners.

This data can be obtained on-line at the following URL: https://coast.noaa.gov/dataviewer

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Users should be aware that temporal changes may have occurred since this data set was collected and some parts of this data may no longer represent actual surface conditions. Users should not use this data for critical applications without a full awareness of its limitations. This product is for informational purposes and may not have been prepared for or be suitable for legal, engineering, surveying, or site specific purposes. Users of this information should review or consult the primary data and information sources to ascertain the usability of the information.

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Vertical accuracy compares the delivered bare-earth digital elevation models (DEMS) with independent ground check points (GCPs) collected by DOGAMI staff. These variations in elevation values were used to produce a mean vertical error and vertical root mean square error (RMSE) value for the entire delivered data set. Project specifications list the maximum acceptable mean vertical offset to be 0.20 meters (0.65 feet) and the maximum vertical RSME to not exceed 0.0925 meters (0.303 feet).

A total of 2425 measured GCP's were obtained in the Metro project area and were compared with the lidar elevation grids. The data delivered to DOGAMI was found to have a mean vertical offset of -0.094 meters (0.308 feet) and an RMSE value of 0.053 meters (0.174 feet). Offset values ranged from -0.667 meters (-2.19 feet) to 0.772 meters (2.53 feet).

For more information about the vertical accuracy, please refer to the final report, listed above in the Supplemental_Information field

of this metadata record.

; Quantitative Value: 0.053 meters, Test that produced the value: The approach adopted for DOGAMI lidar surveys was comprised of three components:

1) Verify the horizontal and vertical coordinates established by Watershed Sciences for a select number of survey monuments used to calibrate the lidar survey. These surveys typically involved a minimum of two hours of GPS occupation over a known point. The collected data were then submitted to the National Geodetic Survey (NGS) Online Positioning User Service (OPUS) for post-processing against several Continuously Operating Reference Stations (CORS) operated by the NGS.

2) Collect GCP's along relatively flat surfaces (roads, paths, parking lots etc.). This step involved the collection of both continuous measurements (from a vehicle as well as from a backpack) as well as static measurements (typically 5 epochs).

3) Having collected the GCP data, the GPS data was post-processed using Trimble Business Center software. Data post-processing typically involved calibrations against at least three CORS stations as well as from local site calibrations performed in the field using those benchmarks that had been independently verified. Data is post processed to refine measurements so that horizontal and vertical errors are less than 0.02 meters (0.065 feet). Horizontal accuracy of data is tested by reoccupying a sample subset of survey monuments used for processing of lidar data. Each occupation's x and y coordinates are compared with the vendor coordinates for offsets.

Lidar data has been collected and processed for all areas within the project study area.

Upon receipt from vendor (WSI), all LiDAR data was independently reviewed by staff from the Oregon Department of Geology and Mineral Industries (DOGAMI) to ensure project specifications were met. All data were inventoried for completeness and data were checked for quality, which included examining LiDAR data for errors associated with internal data consistency, model quality, and accuracy.