Title:Coastal Topography—Fire Island, New York, 07 May 2012 Abstract:
Binary point-cloud data were produced for Fire Island, New York, from remotely sensed, geographically referenced elevation measurements collected by Photo Science, Inc. using an Optech Gemini lidar sensor flown on a Cessna 206 aircraft.
Processed data products are used by the U.S. Geological Survey (USGS) CMGP's National Assessment of Coastal Change Hazards project to quantify the vulnerability of shorelines to coastal change hazards such as severe storms, sea-level rise, and shoreline erosion and retreat. Photo Science, Inc. reports that project specifications are based on the USGS-National Geospatial Program Base Lidar Specification, version 13 and that data are provided in LAS version 1.2 and include ASPRS Class 1: Processed, but unclassified; Class 2: Bare-earth ground; Class 7: Noise; Class 11: Water; Class 14: Bare Water Ocean Surface; Class 17: USGS Overlap Default; Class 18: USGS Overlap Ground.
Planar coordinates are encoded using coordinate pair
Abscissae (x-coordinates) are specified to the nearest 0.5
Ordinates (y-coordinates) are specified to the nearest 0.5
Planar coordinates are specified in meters
The horizontal datum used is North American Datum of 1983 (2007).
The ellipsoid used is Geodetic Reference System 80.
The semi-major axis of the ellipsoid used is 6378137.000000.
The flattening of the ellipsoid used is 1/298.25722210100002.
Altitude_Datum_Name:North American Vertical Datum of 1988 (GEOID09) Altitude_Resolution:0.15 Altitude_Distance_Units:meters Altitude_Encoding_Method:
Explicit elevation coordinate included with horizontal coordinates
Acknowledgment of the U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, as a data source would be appreciated in products developed from these data, and such acknowledgment as is standard for citation and legal practices for data source is expected. Sharing of new data layers developed directly from these data would also be appreciated by the U.S. Geological Survey staff. Users should be aware that comparisons with other datasets for the same area from other periods may be inaccurate because of inconsistencies resulting from changes in photointerpretation, mapping conventions, and digital processes over time. These data are not legal documents and are not to be used as such.
The purpose of this project was to produce a highly detailed and accurate digital elevation map for Fire Island, New York, for use as a management tool and to make these data available to natural-resource managers and research scientists. To ensure that SPCMSC data management protocols were followed, this survey was retroactively assigned a USGS field activity number (FAN), 12CNT09. Additional survey and data details are available at http://cmgds.marine.usgs.gov/fan_info.php?fan=12CNT09. USGS Contract: G10PC00026 Task Order Number: G10PD00588
Photo Science, Inc. reported that Applanix software was used in the post processing of the airborne GPS and inertial data that is critical to the positioning and orientation of the sensor during all flights and that POSPac MMS provides the smoothed best estimate of trajectory (SBET) that is necessary for Optech's post processor to develop the point cloud from the LiDAR missions. They also reported that the point cloud is the mathematical three dimensional collection of all returns from all laser pulses as determined from the aerial mission and at this point this data is ready for analysis, classification, and filtering to generate a bare earth surface model in which the above ground features are removed from the data set. Photo Science, Inc. reported that the point cloud was manipulated within the Optech software; GeoCue, TerraScan, and TerraModeler software was used for the automated data classification, manual cleanup, and bare earth generation from this data and that project specific macros were used to classify the ground and to remove the side overlap between parallel flight lines; also that all data was manually reviewed and any remaining artifacts removed using functionality provided by TerraScan and TerraModeler. They also reported that a new class has been added to the dataset to represent the bare water of the ocean areas collected throughout the project area; ASPRS Class 14 is being used to represent the bare water ocean surface and while attempts were made to remove all extraneous features above the surface of the water, there may be above surface features classified to this class. Photo Science, Inc. reported that some islands below the required collection specifications have been classified to this class as well and that this class was also used during the creation of the ERDAS Imagine Raster DEM files. They also reported that the Ocean Shoreline and Ocean Island breaklines were used to complete the automated classification of these classes within the final LAS files and that all overlap data was processed through automated functionality provided by TerraScan to classify the overlapping flight line data to approved classes by USGS; the overlap data was classified to Class 17 (USGS Overlap Default), and Class 18 (USGS Overlap Ground). Photo Science, Inc. reported that these classes were created through automated processes only and were not verified for classification accuracy and that due to software limitations within TerraScan, these classes were used to trip the Withheld bit within various software packages; these processes were reviewed and accepted by USGS through multiple conference calls and pilot study areas for the LIDAR for the Northeast project (USGS Task Order: G10PD02143 and G10PD01027). They also reported that data were then run through additional macros to ensure deliverable classification levels matching the ASPRS LAS Version 1.2 Classification structure and that GeoCue functionality was then used to ensure correct LAS versioning. Photo Science, Inc. reported that in-house software was used as a final QA/QC check to provide LAS Analysis of the delivered tiles and that QA/QC checks were performed on a per tile level to verify final classification metrics and full LAS header information.
Person who carried out this activity:
Photo Science, Inc.
523 Wellington Way
Hours_of_Service:Monday through Friday 8:00 AM to 5:00 PM (Eastern Time)
Data sources produced in this process:
Date: 24-Jan-2017 (process 2 of 2)
Keywords section of metadata optimized for discovery in USGS Coastal and Marine Geology Data Catalog.
Person who carried out this activity:
How well have the observations been checked?
Photo Science, Inc. reports that the project area required LiDAR to be collected on 0.5 meter GSD or better and processed to meet a bare earth vertical accuracy of 12.5 centimeters RMSEz or better.
How accurate are the heights or depths?
Photo Science, Inc. reports that the Classified LAS files were tested for both vertical and horizontal accuracy and that all data is seamless from one tile to the next, no gaps or no data areas. They also report that the vertical unit of the data file is in decimal meters with 2-decimal point precision and that the reported RMSEz value was determined using the calibration control points, and not the Blind Control. Photo Science, Inc. reports that the calibration control points are the same points that were used to remove any bias in the dataset before bare earth editing and that the listed RMSEz value shown below was calculated from the ground (ASPRS Class 2) data in the final Classified LAS file.
Where are the gaps in the data? What is missing?
Photo Science, Inc. reports that all deliverables meet specifications in contract and that the LAS Files meet ASPRS and USGS Classification Standards at the time of data delivery, including ASPRS classes 1, 2, 7, 11, 14, 17, and 18.
Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. The U.S. Geological Survey requests to be acknowledged as originator of these data in future products or derivative research.
Although these data have been processed successfully on a computer system at the USGS, no warranty expressed or implied is made regarding the display or utility of the data on any other system, or for general or scientific purposes, nor shall the act of distribution constitute any such warranty. The USGS shall not be held liable for improper or incorrect use of the data described and/or contained herein. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.