2014 FEMA Lidar: Ketchikan, Alaska

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Bulk download of data files in LAZ format, geographic coordinates, orthometric heights. Note that the vertical datum (hence elevations) of the files here are different than described in this document.

Information on the NOAA Office for Coastal Management (OCM)

The Data Access Viewer (DAV) allows a user to search for and download elevation, imagery, and land cover data for the coastal U.S. and its territories. The data, hosted by the NOAA Office for Coastal Management, can be customized and requested for free download through a checkout interface. An email provides a link to the customized data, while the original data set is available through a link within the viewer.

This graphic displays the footprint for this lidar data set.

Link to data set quality assurance report.

FEMA M-11 Certificate of Compliance for Ketchikan

Shapefiles for the control monuments, control points, and check points used for the lidar collection and validation.

KETCHIKAN, AK 2ft Contours.

KETCHIKAN, AK 3ft Bare Earth Digital Elevation Models.

KETCHIKAN, AK LiDAR Acquisition vector data.

KETCHIKAN, AK LiDAR Acquisition ground control survey.

KETCHIKAN, AK LiDAR Acquisition Classified LAS Bare Earth point cloud data.

KETCHIKAN, AK LiDAR Acquisition Unclassified LAS raw point cloud data.

Quality Assurace Report for LiDAR and derivative products part of the Technical Support Data Notebook that contains complete narrative on the acquisition and processing of the LiDAR dataset, including area diagram, reports, metadata and other supporting documentation.

KETCHIKAN, AK LiDAR Acquisition Documentation.

Terrain data used for flood risk analysis go through LiDAR preliminary processing and the unclassified point cloud data are tested as specified in the USGS National Geospatial Program Base LiDAR Specification Version 1.0. Where the Mapping Activity Statement (MAS) requires bare earth post-processing of the floodplain area of interest (AOI), the elevation data are tested and comply with both the Fundamental Vertical Accuracy (FVA) and Consolidated Vertical Accuracy (CVA) requirements. Where no bare earth post-processing is specified, only the FVA requirements apply for LiDAR preliminary processing.

Ground Survey:

RTK GPS based surveys were utilized to support both processing and testing of LiDAR data within FEMA designated Areas of Interest (AOIs). Geographically distinct ground points were surveyed using GPS technology throughout the AOIs to provide support for three distinct tasks.

Task 1: Ground control monuments utilized for the STARR Ketchikan LiDAR dataset. Ground control monuments are used to provide redundant control within 13 nautical miles of mission areas for LiDAR flights, as well as the collection of ground control points using real-time kinematic (RTK) survey techniques. The horizontal datum for this dataset is NAD83 (2011), the vertical datum is NAVD88, Geoid 12A, and the data is projected in Alaska State Plane Zone 1. Units are in US Survey Feet.

Task 2: RTK (real time kinematic) ground control points collected for the STARR Ketchikan LiDAR dataset. RTK ground control points are used to correct and verify the vertical accuracy of the LiDAR data. The horizontal datum for this dataset is NAD83 (2011), the vertical datum is NAVD88, Geoid 12A, and the data is projected in Alaska State Plane Zone 1. Units are in US Survey Feet.

Task 3: Land cover class ground check points collected for the STARR Ketchikan LiDAR dataset. Land class ground check points are used to assess the vertical accuracy of the LiDAR data and are collected using real time kinematic (RTK) survey techniques. The horizontal datum for this dataset is NAD83 (2011), the vertical datum is NAVD88, Geoid 12A, and the data is projected in Alaska State Plane Zone 1. Units are in US Survey Feet.

LiDAR Acquisition:

General: LiDAR collection was collected using a Leica ALS70 system mounted in a Piper Navajo airplane. Yielded an average pulse density of >= 4 pulses/square meter over the Ketchikan Project Area.

Swath Acquisition: This swath dataset represents the STARR Ketchikan LiDAR study area. This data is delineated in 4800x4800 ft tiles. Tile naming is derived from the 4 four digits of the easting and first four digits of the northing coordinates of the lower left corner. Data is unclassified (class 0). The horizontal datum for this dataset is NAD83 (2011), the vertical datum is NAVD88, Geoid 12A, and it is projected in Alaska State Plane Zone 1. Units are in US Survey Feet. Quantum Spatial collected the STARR Ketchikan LiDAR data for STARR on 07/12/2014 and 07/13/2014 further information is available in the Ketchikan Post-Flight Aerial Acquisition Report.

All areas were surveyed with an opposing flight line side-lap of >=50% (=100% overlap) in order to reduce laser shadowing and increase surface laser painting. To accurately solve for laser point position (geographic coordinates x, y and z), the positional coordinates of the airborne sensor and the attitude of the aircraft were recorded continuously throughout the LiDAR data collection mission. Position of the aircraft was measured twice per second (2 Hz) by an onboard differential GPS unit, and aircraft attitude was measured 200 times per second (200 Hz) as pitch, roll and yaw (heading) from an onboard inertial measurement unit (IMU).

All swath data were classified as Class 0 or Unclassified.

Leica ALS70 Instrument Parameters:

Beam diameter: 37 cm cm,

Pulse rate: 175 kHz,

Maximum returns: 4,

Speed: 150 knots,

Overlap: 60 %,

Laser power: 93.6 %,

Field of view (FOV): 30 degrees,

Beam wavelength: 1064 nm,

Frequency of GPS sampling: 2 Hz,

Frequency of IMU sampling: 200 Hz,

Swath width: 857 m,

AGL: 5207 - 5315 MSL m,

Average pulse density: 4

Bare Earth Processing:

QSI processing staff initiated a suite of automated and manual techniques to process the data into ASPRS Class 2 Bare Earth. The calibrated and filt ered LiDAR point cloud was hand checked for accuracy. Generate bare earth models as triangulated surfaces. The calibrated and filtered LiDAR point cloud was hand checked for accuracy. All points were placed in one of the following categories: 1 Unclassified, 2 Ground, 7 Noise, and 12 Overlap Points. Model Key points were then generated from the Ground points and placed in Category 8. Requested elevation values were evaluated for the Consolidated Vertical Accuracy (CVA) testing.

Ketchikan Classified LiDAR ASPRS Classifications

1 Unclassified

2 Ground

Point cloud data were received from FEMA in LAS format, NAD83(2011) Alaska State Plane Zone 01 in US survey feet horizontally and vertically. The vertical datum was NAVD88 from Geoid12a. NOAA OCM reprojected to geographic coordinates and transformed the vertical coordinate system to height above the NAD83 ellipsoid in meters by reversing the Geoid12a model. Data were then ingested into the Digital Coast Data Access Viewer for distribution.

Examination of the data indicated points were only in classes 1 and 2.