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Short Citation:
OCM Partners, 2024: 2006 Federal Emergency Management Agency (FEMA) Topographic LiDAR: Connecticut Coastline Survey,

Item Identification

Title: 2006 Federal Emergency Management Agency (FEMA) Topographic LiDAR: Connecticut Coastline Survey
Short Name: ct2006_fema_coastal_m1468_metadata
Status: Completed
Publication Date: 2013-04

LIDAR data is remotely sensed high-resolution elevation data collected by an airborne collection platform. By positioning laser range finding with the use of 1 second

GPS with 100hz inertial measurement unit corrections; Terrapoint's LIDAR instruments are able to make highly detailed geospatial elevation products of the ground,

man-made structures and vegetation. The LiDAR flightlines for this project was planned for a 50% acquisition overlap. The nominal resolution of this project

without overlap is 1.25m. Four returns were recorded for each pulse in addition to an intensity value. GPS Week Time, Intensity, Flightline and number attributes were

provided for each LiDAR point. Data is provided as random points, in LAS v1.0 format, classified according to ASPRS Class Code 2=Ground 1=Undefined. Water is included

in the bare earth ground model, except where the entire tile is covered by water.

The following regions of Connecticut are included in this project:

Fairfield County - 130 square kilometers

New Haven - 170 square kilometers

Middlesex - 29 square kilometers

New London - 157 square kilometers

Please note that the LiDAR intensity is not calibrated or normalized. The intensity value is meant to provide relative signal return strengths for features imaged by the



The purpose of this LiDAR data was to produce high accuracy 3D elevation based geospatial products for coastal flood mapping.



Supplemental Information:

A footprint of this data set may be viewed in Google Earth at:

A field survey report is available at:

A QA/QC report is available at:


Theme Keywords

Thesaurus Keyword
ISO 19115 Topic Category
None ASPRS standards
None OPTECH_3100EA

Physical Location

Organization: Office for Coastal Management
City: Charleston
State/Province: SC

Data Set Information

Data Set Scope Code: Data Set
Maintenance Frequency: As Needed
Data Presentation Form: las
Entity Attribute Overview:

LiDAR point data in LAS 1.0 format

ASPRS cassfication scheme (1 = undefined; 2 = ground)

Contains the following fields of information:

Class, GPS WeekTime, Easting, Northing, Elevation, Echo Number, Echo, Intensity, Flightline

Entity Attribute Detail Citation:


Distribution Liability:

Any conclusions drawn from the analysis of this information are not the responsibility

of Dewberry & Davis LLC, Terrapoint USA, FEMA, NOAA, the Office for Coastal Management or its partners.

Support Roles

Data Steward

CC ID: 671437
Date Effective From: 2013-04
Date Effective To:
Contact (Organization): NOAA Office for Coastal Management (NOAA/OCM)
Address: 2234 South Hobson Ave
Charleston, SC 29405-2413
Email Address:
Phone: (843) 740-1202


CC ID: 671439
Date Effective From: 2013-04
Date Effective To:
Contact (Organization): NOAA Office for Coastal Management (NOAA/OCM)
Address: 2234 South Hobson Ave
Charleston, SC 29405-2413
Email Address:
Phone: (843) 740-1202

Metadata Contact

CC ID: 671440
Date Effective From: 2013-04
Date Effective To:
Contact (Organization): NOAA Office for Coastal Management (NOAA/OCM)
Address: 2234 South Hobson Ave
Charleston, SC 29405-2413
Email Address:
Phone: (843) 740-1202

Point of Contact

CC ID: 671438
Date Effective From: 2013-04
Date Effective To:
Contact (Organization): NOAA Office for Coastal Management (NOAA/OCM)
Address: 2234 South Hobson Ave
Charleston, SC 29405-2413
Email Address:
Phone: (843) 740-1202


Currentness Reference: Ground Condition

Extent Group 1

Extent Group 1 / Geographic Area 1

CC ID: 1133609
W° Bound: -73.659952
E° Bound: -71.829101
N° Bound: 41.540542
S° Bound: 40.979296

Extent Group 1 / Time Frame 1

CC ID: 1133608
Time Frame Type: Range
Start: 2006-12-16
End: 2006-12-18

Spatial Information

Spatial Representation

Representations Used

Vector: Yes

Access Information

Security Class: Unclassified
Data Access Procedure:

This data can be obtained on-line at the following URL:


Data Access Constraints:


Data Use Constraints:

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. These data depict the heights at the time of the survey and are only accurate for that time.

Distribution Information

Distribution 1

CC ID: 740572
Download URL:
File Name: Customized Download

Create custom data files by choosing data area, product type, map projection, file format, datum, etc.

Distribution 2

CC ID: 740573
Download URL:
File Name: Bulk Download

Simple download of data files.



CC ID: 740575
URL Type:
Online Resource


CC ID: 740576
URL Type:
Online Resource

Activity Log

Activity Log 1

CC ID: 671459
Activity Date/Time: 2016-05-23

Date that the source FGDC record was last modified.

Activity Log 2

CC ID: 671458
Activity Date/Time: 2017-11-14

Converted from FGDC Content Standards for Digital Geospatial Metadata (version FGDC-STD-001-1998) using '' script. Contact Tyler Christensen (NOS) for details.

Activity Log 3

CC ID: 718201
Activity Date/Time: 2018-02-08

Partial upload of Positional Accuracy fields only.

Activity Log 4

CC ID: 740574
Activity Date/Time: 2018-03-13

Partial upload to move data access links to Distribution Info.

Data Quality


Raw elevation measurements have been tested to 0.23 feet vertical accuracy at 95 percent confidence level

Horizontal Positional Accuracy:

Compiled to meet 1 meter horizontal accuracy at the 95 percent confidence level

Vertical Positional Accuracy:

Independent accuracy testing was performed by Dewberry & Davis using 80 high accuracy quality control checkpoints distributed throughout the project in four major land cover types (open terrain, weeds/crops,

forest, urban). Dewberry used testing procedures consistent with those specified in the National Standard for Spatial Data Accuracy (NSSDA) as well as LiDAR accuracy testing guidelines and specifications published by the

Federal Emergency Management Agency (FEMA), National Digital Elevation (NDEP), and American Society for Photogrammetry and Remote Sensing (ASPRS).

; Quantitative Value: 0.10 meters, Test that produced the value:

Value in meters. Connecticut LiDAR dataset tested 0.10m(.34ft) vertical accuracy at 95% confidence level in open terrain, based on open terrain RMSEz (.17ft) x 1.9600; tested 0.13m (.43ft) vertical accuracy at 95% confidence

level in all land cover categories combined, based on consolidated RMSEz (.22ft) x 1.9600.

Completeness Report:

According to Terrapoint standards; the following aspects of the LiDAR data was verified during the course of the project processing:

-Data completeness and integrity

-Data accuracy and errors

-Anomaly checks through full-feature hillshades

-Post automated classification Bare-earth verification

-RMSE inspection of final bare-earth model using kinematic GPS

-Final quality control of deliverable products; ensuring integrity; graphical quality; conformance to Terrapoint standards are met for all delivered products.

Conceptual Consistency:

All LiDAR files delivered were verified and tested to ensure they open and are positioned properly.


Process Steps

Process Step 1

CC ID: 1133604

- General Overview

The Airborne LiDAR survey was conducted using an OPTECH 3100EA flying at a nominal height of 1550 metres AGL with a total angular coverage of 40 degrees. Flight line spacing

was nominally 564 metres providing overlap of 50% on adjacent flight lines. Lines were flown in east/west and north/south orientated blocks to best optimize flying time

considering the layout for the project.

- Aircraft

A Piper Navajo, registration C-FQQB was used for the survey. This aircraft has a flight range of approximately 6.5 hours and was flown at an average altitude of 1550,

thereby encountering flying altitudes of approximately 1550 metres above sea level (ASL). The aircraft was staged from the East Haven CT Airport, and ferried daily to the project

site for flight operations.

- GPS Receivers

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.

- Number of Flights and Flight Lines

For both Connecticut and Rhode Island Coastline Sites; a total of 6 missions were flown for this project with flight times ranging approximately 31 hours under good

meteorological and GPS conditions. 72 flight lines were flown over the Connecticut Coastline site to provide complete coverage.

Process Date/Time: 2007-12-01 00:00:00

Process Step 2

CC ID: 1133605

- Airborne GPS Kinematic

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 4.5. Distances from base station to aircraft were kept to a maximum of 35 km, to ensure a strong OTF (On-The-Fly) solution. For

all flights, the GPS data can be classified as excellent, with GPS residuals of 5cm average but no larger than 12 cm being recorded.

- Calculation of 3D laser points (raw data)

The post-processing software to derive X, Y, Z values from roll, pitch, yaw, and range is Optech's Realm.

- Classification and Editing

The data was processed using the software TerraScan, and following the methodology described herein. The initial step is the setup of the TerraScan project, which is done

by importing client provided tile boundary index encompassing the entire project areas. The 3D laser point clouds, in binary format, were imported into the TerraScan

project and divided in 1407 tiles, as per the contract specifications. tiled, the laser points were classified using a proprietary routine in TerraScan. This routine removes

any obvious outliers from the dataset following which the ground layer is extracted from the point cloud. The ground extraction process encompassed in this routine takes place

by building an iterative surface model. This surface model is generated using three main parameters: building size, iteration angle and iteration distance. The

initial model is based on low points being selected by a "roaming window" with the assumption is that these are the ground points. The size of this roaming window is

determined by the building size parameter. The low points are triangulated and the remaining points are evaluated and subsequently added to the model if they meet the iteration

angle and distance constraints. This process is repeated until no additional points are added within an iteration. A second critical parameter is the maximum terrain angle

constraint, which determines the maximum terrain angle allowed within the classification model. The data is then manually quality controlled with the use of

hillshading, cross-sections and profiles. Any points found to be of class vegetation, building or error during the quality control process, are removed from the ground model

and placed on the appropriate layer. An integrity check is also performed simultaneously to verify that ground features such as rock cuts, elevated roads and crests are

present. Once data has been cleaned and complete, it is then reviewed by a supervisor via manual inspection and through the use of a hillshade mosaic of the entire project area.

- Projection Transformation

The data was processed in the native UTM zone in meters and then transformed to the Connecticut State Plane final projection system and US survey feet using an

in-house transformation software which uses the Coorpscon DLL.

Process Date/Time: 2007-01-01 00:00:00

Process Step 3

CC ID: 1133606

The NOAA Office for Coastal Management (OCM) received the topographic files in LAZ V1.0 format. The files contained lidar elevation measurements.

The data were received in Connecticut State Plane coordinates, NAD83 (Zone 0600) and were vertically referenced to NAVD88 using the Geoid03 model. The vertical units of the data were feet.

OCM performed the following processing for data storage and Digital Coast provisioning purposes:

1. The topographic las files were converted from a Projected Coordinate System (Connecticut SP 0600) to a Geographic Coordinate system (NAD83).

2. The topographic las files' horizontal units were converted from US survey feet to decimal degrees.

3. The topographic las files were converted from orthometric (NAVD88) heights to ellipsoidal heights using Geoid03.

4. The topographic las files' vertical units were converted from survey feet to meters.

Process Date/Time: 2013-04-01 00:00:00

Catalog Details

Catalog Item ID: 49654
GUID: gov.noaa.nmfs.inport:49654
Metadata Record Created By: Anne Ball
Metadata Record Created: 2017-11-15 15:21+0000
Metadata Record Last Modified By: SysAdmin InPortAdmin
Metadata Record Last Modified: 2022-08-09 17:11+0000
Metadata Record Published: 2022-03-16
Owner Org: OCMP
Metadata Publication Status: Published Externally
Do Not Publish?: N
Metadata Last Review Date: 2022-03-16
Metadata Review Frequency: 1 Year
Metadata Next Review Date: 2023-03-16