2007 Northwest Florida Water Manangement District(NWFWMD) Lidar: Gadsden County

LIDAR-derived binary (.las) files containing points classified as bare-earth and canopy (first return) were produced for the 2007 Northwest Florida

Water Management District - Gadsden County, Florida lidar mapping project. The files were provided in a scheme of FDEM-derived 5,000 x 5,000 foot

(1500 x 1500 meter) tiles. Horizontal mapping units are in UTM meters, vertical mapping units are in U.S. survey feet. The total mapping area

covers 535 square miles of Gadsden County, Florida.

Original contact information:

Contact Name: Mr. John Crowe

Contact Org: Northwest Florida Water Management District

Title: Director, Division of Resource Management

Phone: 850-539-5999

Email: john.crowe@nwfwmd.state.fl.us

The purpose of the project is to produce accurate, high-resolution data for planning, analysis, and for use with other data sets. Merrick &

Company obtained LiDAR data over approximately 535 square miles covering the majority of Gadsden County, Florida. The LiDAR data has been processed

to result in a data set that is suitable for the future generation of 2-foot contours.

These data will be used to support FEMA's Map Modernization Program through the creation of high-resolution digital elevation models (DEMs). These

DEMs support a variety of applications, including improved floodplain delineation, hydrologic and hydraulic modeling, hazard mapping as well as

other planning activities.

10516

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

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/583/supplemental/2007_NWFWMD_Gadsden_County_Lidar.kmz

The Lidar Mapping Report (including sensor information, collection parameters, etc.) for this data set may be viewed at:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/583/supplemental/NWFWMD_Gadsden_County_Lidar_Mapping_Report.pdf

Lidar points are attributed with the following classifications:

1 - canopy

2 - ground (bare earth)

9 - water

Lidar intensity values range from 0-255. Lidar return values range from 1-3. Flight line numbers range from 1-19.

All deliverables meet specifications in contract. LAS Files meet ASPRS Classification Standards.

Any conclusions drawn from the analysis of this information are not the responsibility of NOAA, the Office for Coastal Management

or its partners.

This data can be obtained on-line at the following URL: https://coast.noaa.gov/dataviewer

The data set is dynamically generated based on user-specified parameters.

;

none

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.

Microsoft Windows XP version 5.1 (Build 2600, Service Pack 2); ArcGIS Desktop 9.1; ArcGIS Workstation 9.1; MARS 4.0

Verification of attribute accuracy of LIDAR data involves the use of filtering techniques. Auto-filtering uses algorithms to reclassify data in

the point cloud. Hand-filtering involves the use of a technician working in a graphic environment to reclassify the erroneous points that may

remain in the LIDAR point cloud after auto filter.

Horizontal accuracy is verified in three tests. During boresighting, adjoining flightlines are view in profile and hard edged features are

observed and if necessary the flightlines are adjusted for good relative horizontal and vertical fit. The second test for horizontal accuracy

is by comparing raw contours from each flightline against adjoining flightlines at specific points. The final test is the vertical LIDAR control

report.

Survey control points were used to validate the accuracy of the LIDAR surface model after automatic and hand filtering. This surface exceeds the

NSSDA consolidated vertical accuracy specifications of 36.3 cm (1.19ft) at the 95% confidence level.

; Quantitative Value: 0.078 meters, Test that produced the value: RMSEz (m) based upon comparison with 45 survey checkpoints.

This dataset contains classified returns of the LIDAR sensor. The sensor data was verified in MARS software to ensure complete

coverage.

Calibrations of the LIDAR flightline data are performed; this process is known as boresighting. The flightlines are compared to evaluate both their

relative and absolute accuracies.