2007 Northwest Florida Water Management District (NWFWMD) Lidar: North Jefferson County

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Type of LiDAR Scanner = LH Systems ALS50 Data Acquisition Height = 700 meters AGL Scanner Field Of

View = 40 degrees Scan Frequency = 35 Hertz Pulse Repetition Rate - 50 Kilohertz Aircraft Speed = 120 KIAS Swath Width

= +/- 20 degrees Nominal Ground Sample Distance = 0.7 meters Number of Returns per Pulse = 5 (first, last, intermediate)

Distance Between Flight Lines = 365 meters

| Source Geospatial Form: Model | Type of Source Media: Digital Tape Media

Data Collection:

Using a LH Systems ALS50 Light Detection And Ranging (LiDAR) system, 262 flight lines of high density (submeter ground

sample distance) data were collected over the northern half of Jefferson County in Florida. This data was collected at

the same time as the collection for portions of Bay, Calhoun, Jackson and Washington Counties. Collectively,

these data sets cover approximately 1201 square miles. The Jefferson County project covers approximately 513 square miles.

The data acquisition occurred in 17 missions between February 22, 2007 and March 13, 2007. Multiple returns were recorded

for each laser pulse along with an intensity value for each return.

During the LIDAR campaign, the Sanborn field crew conducted a GPS field survey to establish final coordinates of the ground

base stations for final processing of the base-remote GPS solutions. Four (4) airborne global positioning system (GPS) base

stations were used to support the LiDAR data acquisition. GPS ground control check points were also collected by the LiDAR

team while onsite for product accuracy validation and delivery.

Airborne GPS Processing:

Airborne GPS data was differentially processed and integrated with the post processed IMU data to derive a smoothed best

estimate of trajectory (SBET). The SBET was used to reduce the LiDAR slant range measurements to a raw reflective surface

for each flight line. The overlap between flight lines was removed to provide a homogeneous coverage, and the coverage was

classified to extract a bare earth digital elevation model (DEM). Airborne GPS is differentially processed using the

GrafNAV V7.50 software by Waypoint Consulting of Calgary, Alberta, Canada.

The PDOP and distance separation is as follows:

IMU data is processed using the PosPac V4.2 software by Applanix Corporation of Richmond Hill, Ontario, Canada. The

reflective surface is derived using the ALS Post Processor software by Leica Geosystems GIS & Mapping Division of Atlanta,

Georgia. The classification and quality control (QC) of LiDAR data is carried out using TerraScan software by Terrasolid

Limited of Helsinki, Finland.

IMU data Processing:

IMU data provides information concerning roll, pitch and yaw of collection platform during collection event. IMU

information allows the pulse vector to be properly placed in 3D space allowing the distance from the aircraft reference

point to be properly positioned on the elevation model surface. IMU data is processed using the PosPac V4.2 software by

Applanix Corporation of Richmond Hill, Ontario, Canada.

Reflective Surface Generation:

The reflective surface is derived using the ALS Post Processor software by Leica Geosystems GIS & Mapping Division of

Atlanta, Georgia.

LIDAR Ground Point Classification:

The classification and quality control (QC) of LiDAR Ground point class is carried out using TerraScan software by

Terrasolid Limited of Helsinki, Finland. In the filtering process points are classified as Ground or one of several

non-Ground classes including Unclassified, Overlap, and Low Points.

Reclassification of Water Points:

LiDAR returns from open water surfaces are commonly included in the Ground class by the ground filtering algorithms.

Using 2D and 3D visualization methods, 2D vector polygons were digitized for significant waterways and water bodies that

were readily identifiable in the LiDAR data. These polygons were then used to re-classify points in open water from the

filtered Ground class to the Water class.

Coordinate Reprojection:

Output LAS Files LIDAR points maintained in UTM coordinate system converted to Geographic projection with units of Decimal

Degrees

The NOAA Office for Coastal Management (OCM) received files in LAS format. The files contained LiDAR intensity

and elevation measurements. OCM performed the following processing on the data to make it available within the LiDAR Data

Retrieval Tool (LDART):

1. The data were converted from NAVD88 (orthometric) heights to GRS80 (ellipsoid) heights using Geoid 03.

2. The LAS header fields were sorted by latitude and updated.

3. The data was filtered to eliminate outliers.