Data Management Plan

Digital Elevation model, derived from a lidar point cloud data, developed to support FEMA flood risk analysis and mapping in Ketchikan, Alaska. Point cloud is classified as ground (class 2) and other (class 1). The data was collected under a FEMA contract to the Strategic Alliance for Risk Reduction (STARR) with an accuracy requirement to support 2-foot contours. Original tasking indicates additional classes would be populated (7, 9, 10, 11), but they are not in the data set.

Process Steps:

• 2014-09-30 00:00:00 - 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.
• 2014-07-01 00:00:00 - 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.
• 2014-07-13 00:00:00 - 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
• 2014-09-30 00:00:00 - 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
• 2018-05-01 00:00:00 - Digital Elevation Model tiles were received in ESRI Arc coverage proprietary format from FEMA. Tiles were in Alaska state plane zone 01 US survey feet with vertical units of US survey feet. The vertical datum was NAVD88 using the NGS Geoid12a geoid model. Data were converted to tif format and changed to horizontal and vertical meters for ingest in the Digital Coast Data Access Viewer. The change of horizontal units was done because the system was not processing the files in US survey feet correctly. This projection does not have an EPSG code. EPSG code 6394 was used for Alaska State Plane Zone 1 NAD83(2011) in meters. Tests showed this data was correctly interpreted in some software, but not all software. The data in both feet and meters is available on the bulk download data access link. (Citation: Ketchikan 3ft Digital Elevation Models)

Data is available online for custom downloads