2005 St. Johns River Water Management District (SJRWMD) Lidar: Western Seminole County, Florida

This data set consists of a bare earth data set of 498 files covering a geographic area of 175 square miles in

western Seminole County, Florida and includes small portions of adjacent Orange and Lake Counties. The lidar data was

collected June 5-7, 2005. This data set seems to contain only model keypoints (points that are a thinned data set that is

intended to remove extraneous data such as trees and points that are deemed redundant to the final bare earth product)

that are classified as ground points. As a result, there are a lower number of points than in a full mass point lidar data

set; and it is recommended that the data be downloaded as points and used with a TIN (Triangulated Irregular Network)

or similar algorithm to produce a bare earth surface.

Original contact information:

Contact Name: Paul Finer

Contact Org: St. Johns River Water Management District (SJRWMD)

Phone: 386-329-4542

Email: gis_support@sjrwmd.com

This data set depicts information about geographic features within the project area and is to be used for purposes

defined by the SJRWMD.

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The Consolidated, Fundamental and Supplemental Vertical Accuracy Reports and the Photogrammetric

Survey and Map Report may be viewed at: https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/101/supplemental/index.html

Any conclusions drawn for the analysis of this information are not the responsibility of the St. Johns

River Water Management District (SJRWMD), 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data may no longer represent actual surface conditions.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.

The LiDAR data was compiled to meet a 7.6-foot horizontal accuracy at 95-percent confidence level. Due to the coarse nature

of the LiDAR data no comparisons could be made between the intensity returns and the horizontal positions of field surveyed

points. Project planning for high resolution LiDAR data and proven system performance were used to determine the expected

horizontal accuracy.

Final map data are referenced to the Florida High Accuracy Reference Network (HARN) adjustment for the North American Datum

of 1983. Projection was Universal Transverse Mercator (UTM), Zone 17, units were meters.

The LiDAR data was tested for a fundamental vertical accuracy and a supplemental vertical accuracy. The fundamental accuracy was

tested for points that fall in open areas, not obscured by vegetation, having a normalized distribution. The supplemental

accuracy was tested for points that fall in areas of vegetation, where data does not follow a normalized distribution.

The fundamental vertical accuracy was tested 0.56-foot vertical accuracy at 95 percent confidence level using RMSE procedures

with no outliers. The vertical root mean square error (RMSEz) was tested at 0.29-foot. The fundamental vertical accuracy meets

the National Standards for Spatial Data Accuracy (NSSDA) for one-foot contours. These results were determined by comparing

thirty-nine (39) field surveyed points obtained on hard surface and open areas with the Bald Earth Last Return LiDAR data.

Refer to file 05680_fundamental_vert_acc.xls to view the results including summary statistics, normalized distribution, and a

histogram.

The supplemental vertical accuracy was tested 1.29-feet vertical accuracy at 95 percent confidence level, determined by

the 95th percentile method. Point M3 having a -1.94 feet difference was determined to be an outlier. These results were

determined by comparing forty (40) field-surveyed points obtained in brush and forested areas with the Bald Earth Last

Return LiDAR data. Refer to file 05680_supplemental_vert_acc.xls to view the results including summary statistics,

normalized distribution, and a histogram. Another analysis of the data will be made after the manual edit of the LiDAR data

that may change these results.

Ground control surveys were conducted under the supervision of a licensed Florida Surveyor and Mapper in accordance with

Florida State Statutes. Horizontal values were referenced to the Florida High Accuracy Reference Network (HARN) adjustment

for the North American Datum of 1983. Projection was Universal Transverse Mercator (UTM), Zone 17, units were meters. Vertical

values were referenced to North American Vertical Datum of 1988 (NAVD88) units were feet. GPS and conventional

survey methodology was used to generate the values of the surveyed points located throughout the project area.

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