2010 U.S. Geological Survey (USGS) Topographic Lidar: Channel Islands, California

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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.

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Terrapoint used their latest helicopter-based LiDAR sensor. The Riegl LMS-Q560 helicopter-mounted system is designed specifically for small block

sites and corridor applications.

A combination of Sokkia GSR 2600 and NovAtel DL-4+ dual-frequency GPS receivers were used to support the airborne operations of this survey

and to establish the GPS control network.

Airborne GPS kinematic data was processed on-site using GrafNav kinematic On-The-Fly (OTF) software. Flights were flown with a minimum of 6

satellites in view (13o above the horizon) and with a PDOP of better than 4. Distances from base station to aircraft were kept to a maximum of 24 km.

For all flights, the GPS data can be classified as excellent, with GPS residuals of 3cm average or better but no larger than 10cm being recorded.

The initial step of calibration is to verify availability and status of all needed GPS and Laser data against field notes and compile any data if

not complete. Laser data points are generated using Terrapoint's proprietary laser post-processing software. This software combines the raw

laser range and angle data file with the finalized GPS/IMU information. The resulting point cloud has been projected into the desired coordinate

system in LAS binary format. All missions are validated against the adjoining missions for relative vertical biases and collected GPS kinematic

ground truthing points for absolute vertical accuracy purposes. On a project level, a coverage check is carried out to ensure no slivers are

present in areas where it was possible to acquire LiDAR at a safe AGL.

Dewberry utilizes a variety of software suites for inventory management, classification, and data processing. All LiDAR related processes begin by

importing the data into the GeoCue task management software. GeoCue allows the data to retain its delivered tiling scheme (2000 m by 2000 m). The

tiled data is then opened in Terrascan where Dewberry uses proprietary ground classification routines to remove any non-ground points and generate an

accurate ground surface. The ground routine consists of three main parameters (building size, iteration angle, and iteration distance); by adjusting

these parameters and running several iterations of this routine an initial ground surface is developed. The building size parameter sets a roaming

window size. Each tile is loaded with neighboring points from adjacent tiles and the routine classifies the data section by section based on this

roaming window size. The second most important parameter is the maximum terrain angle, which sets the highest allowed terrain angle within the model.

Once the ground routine has been completed a manual quality control routine is done using hillshades, cross-sections, and profiles within the

Terrasolid software suite. After this QC step, a peer review and supervisor manual inspection is completed on a percentage of the classified tiles

based on the project size and variability of the terrain. After the ground classification corrections were completed, the dataset was processed

through a water classification routine that utilizes breaklines compiled by Dewberry to automatically classify hydrographic features. The water

classification routine selects ground points within the breakline polygons and automatically classifies them as class 9, water. During this water

classification routine, points which are in close proximity (2 ft) to the hydrographic features are moved to class 10, an ignored ground. In

addition to classes 1, 2, 9, and 10, St. Johns allows for a Class 7, noise points. This class was only used if needed when points could manually

be identified as low/high points.

The fully classified dataset is then processed through Dewberry's comprehensive quality control program.

The data were classified as follows:

Class 1 = Unclassified. This class includes vegetation, buildings, noise etc.

Class 2 = Ground

Class 7 = Noise

Class 9 = Water

Class 10= Ignored Ground

The LAS header information was verified to contain the following:

Class (Integer)

GPS Week Time (0.0001 seconds)

Easting (0.01 foot)

Northing (0.01 foot)

Elevation (0.01 foot)

Echo Number (Integer 1 to 4)

Echo (Integer 1 to 4)

Intensity (8 bit integer)

Flight Line (Integer)

Lidar Scan Angle (Integer degree)

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

The data were received in UTM Zones 10 and 11 (NAD83) coordinates and were vertically referenced to NAVD88 using the Geoid09 model. The vertical

units of the data were meters. OCM performed the following processing for data storage and Digital Coast provisioning purposes:

1. The topographic las files were converted from orthometric (NAVD88) heights to ellipsoidal heights using Geoid09.