2005 Southwest Florida Water Management District (SWFWMD) Lidar: Manatee District

The Light Detection and Ranging (LiDAR) LAS dataset is a survey of select areas within Southwest Florida. These data

were produced for the Southwest Florida Water Management District (SWFWMD). The Manatee / Little Manatee LiDAR Survey project

area consists of approximately 176 square miles. This data set falls in Manatee County. The LiDAR point cloud was flown at a

density sufficient to support a maximum final post spacing of 6 feet for unobscured areas. 3001 inc. acquired 445 flightlines

between February 11, 2005 and April 14, 2005. The data was divided into 5000' by 5000' foot cells that serve as the tiling

scheme. The Manatee / Little Manatee LiDAR Survey was collected under the guidance of a Professional Mapper/Surveyor.

Original contact information:

Contact Org: Southwest Florida Water Management District (SWFWMD)

Phone: 352-796-7211

The Southwest Florida Water Management District uses topographic information to support regulatory, land management

and acquisition, planning, engineering, and habitat restoration projects. The Manatee / Little Manatee LiDAR Survey data

will support the creation of Federal Emergency Management Agency Flood Insurance Rate Maps (FEMA FIRM) and an integrated

ground and surface water model for the Peace River Watershed. All data will be public record as defined by applicable

Florida statutes. The Manatee / Little Manatee LiDAR Survey was collected under the guidance of a licensed and professional

Surveyor and Mapper.

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3001 inc. also acquired 97 flightlines between April 3, 2005 and April 11, 2005 for the Little Manatee

District data set. The information in this report is the result of the LiDAR surveys performed on the dates indicated and the

general conditions at the time.

The Little Manatee and Manatee Ground Control Survey Report may be viewed at:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/66/supplemental/index.html

Any conclusions drawn for the analysis of this information are not the responsibility of the Office for Coastal Management or its partners.

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

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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this data may no longer represent actual surface conditions.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.

ArcInfo 9.0

Stream shore lines and 2-D coordinate line strings were collected as breaklines using LiDAR that

was acquired and processes to FEMA specifications. These breaklines were created from on-screen digitizing using a

combination of the LiDAR points and the orthophotography. Attributes were verified using routines that verify the vertical

and horizontal positions of the breaklines.

All ground control processing and adjustment is performed using published coordinate

horizontal and vertical datums (e.g. NGS CORS). For deliverables, Corpscon for Windows Version 5.11.08 (geoid 99) was

used for horizontal and vertical datum conversion as well as for coordinate system conversion purposes (e.g. UTM to State

plane). Compiled to meet 1.0 meter horizontal accuracy at the 95% confidence level.

The accuracy assessment was performed using a standard method to compute the root mean

square error (RMSE) based on a comparison of ground control points (GCP) and filtered LiDAR data points. Filtered LiDAR data

has had vegetation and cultural features removed and by analysis represents bare earth elevations. Testing was performed

prior to gridding of the filtered LiDAR data points and construction of the Intergraph .dtm file format. The RMSE figure

was used to compute the vertical National Standard for Spatial Data Accuracy (NSSDA). Ground control was established by 3001,

Inc. A spatial proximity analysis was used to select edited LiDAR data points contiguous to the relevant GCPs. A search

radius decision rule is applied with consideration of terrain complexity, cumulative error and adequate sample size.

Cumulative error results from the errors inherent in the various sources of horizontal measurement. These sources include

the airborne GPS, GCPs and the uncertainty of the accuracy of the LiDAR data points. This accuracy is achieved prior to

the subsampling that occurs through integration with the inertial measurement unit (IMU) positions that are recorded. It

is unclear at this time whether the initial accuracy is maintained. The horizontal accuracy of the GCPs is estimated to be

in the range of approximately 1 to 1.6 inches. Finally, sample size was considered. The specification for the National

Standard for Spatial Data Accuracy is a minimum of 20 points to conduct a statistically significant accuracy evaluation

(Minnesota Planning, 1999, Positional Accuracy Handbook, Minnesota Planning Land Management Information Center, St. Paul,

Minnesota., p.3). Most statistical texts indicate that a minimum of 30 sample points provide a reasonable Approximation of

a normal distribution. The intent of the NSSDA is to reflect the geographic area of interest and the distribution of error

in the data set (Federal Geographic Data Committee, 1998, Geospatial National Standard for Spatial Data Accuracy,

Federal Geographic Data Committee Secretariat, Reston, Virginia, p.3-4). Additional steps were taken to ensure the vertical

accuracy of the LiDAR data including:

Step 1: Precision Bore sighting (Check Edge-matching)

Step 2: Compare the LiDAR data to the Field Survey (Field survey is to FEMA specifications and more stringent internal

specifications)

Step 3: Automated Filtering

Step 4: Manual Editing (Quality Control)

Step 5: 3-D digitizing and Photogrammetric Compilation of hydrographic breaklines

RMSE is 4.75 cm (0.156 feet) and the Vertical Accuracy is 9.33 cm (0.306 feet) at the 95% confidence level.

Cloud Cover: 0

The LAS files were flown at a density sufficient to support a maximum final post spacing of 6 feet for

unobscured areas. The bare-earth surface will contain voids in areas that were densely vegetated, covered by bridges,

buildings, water, fresh asphalt, sand etc.

The LAS files were flown at a density sufficient to support a maximum final post spacing of 6 feet

for unobscured areas. 3001 inc. also acquired 97 flightlines between April 3, 2005 and April 11, 2005 for the Little Manatee

District data set. The data was divided into 5000' by 5000' foot cells that serve as the tiling scheme. The Manatee / Little

Manatee LiDAR Survey was collected under the guidance of a Professional Mapper/Surveyor.