2005 Southwest Florida Water Management District (SWFWMD) Lidar: Little 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 and Little Manatee LiDAR Survey project area

consists of approximately 176 square miles. This data set falls in a portion of Hillsborough and Manatee counties. 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

97 flightlines between April 3-11, 2005. The data was divided into 5000' by 5000' foot cells that serve as the tiling scheme. The

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.

10666

The metadata are not complete if the format is not compatible with ArcGIS 9, if it is not FDGC Compliant

and if copies of the survey report in PDF format, are not delivered as an attachment. 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/geoid18/67/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;

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data may no longer represent actual surface conditions.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.

ArcInfo 9.0

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

acquired and processed 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. acquired 97 flightlines between April 3, 2005 and April 11, 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.