2009-2012 Indiana Statewide Imagery and LiDAR Program: Maumee River Basin Counties

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The LiDAR data collected for this task order. | Source Geospatial Form: vector digital data | Type of Source Media: disc

Block 7(partial) and 8 - Using an Optech Gemini LiDAR system, 152 flight lines of high density

data, at a nominal pulse spacing (NPS) of 1.5 meter (1.0 meters for Floyd and Dearborn Counties)and Blocks 5, 6, and

7(partial) - Using Leica ALS LiDAR systems, 219 flight lines of high density data were collected, at a nominal

pulse spacing (NPS) of 1.5 meter. Multiple returns were recorded for each laser pulse along with an intensity value

for each return. A total of thirty (30) missions were flown January 31, 2012 December 13, 2012. Eleven (11) airborne

global positioning system (GPS) base stations were used in support of the LiDAR data acquisition. 248 ground

control points were surveyed through static methods. The geoid used to reduce satellite derived elevations to

orthometric heights was Geoid09. The horizontal datum used for this survey is North American Datum 1983 (NSRS2007),

Indiana State Plane Coordinate System, East Zone, and expressed in US Survey Feet. The vertical datum used for this

survey is North American Vertical Datum 1988 (NAVD88), and expressed in US Survey Feet. 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. System Parameters: - Type of Scanner = Optech Gemini - Data Acquisition Height = 7,380-feet AGL

- Scanner Field of View = 20 degrees - Scan Frequency = 32 Hertz - Pulse Repetition Rate - 100.0 Kilohertz -

Aircraft Speed = 150 Knots - Swath Width = 5374 feet - Number of Returns Per Pulse = Maximum of 4 - Distance

Between Flight Lines = Varies. System Parameters: - Type of Scanner = Leica ALS50-II / ALS60 / ALS70 - Data

Acquisition Height = 7800 feet AGL - Scanner Field of View = 40 degrees - Scan Frequency = Varies - Pulse

Repetition Rate - 99 Kilohertz - Aircraft Speed = Varies - Swath Width = 5678 feet - Number of Returns Per

Pulse = Maximum of 4 - Distance Between Flight Lines = Varies.

The Optech Gemini and Leica systems' LiDAR system calibration and performance is verified

on a periodic basis using Woolpert's calibration range. The calibration range consists of a large building and runway.

The edges of the building and control points along the runway have been located using conventional survey methods.

Inertial measurement unit (IMU) misalignment angles and horizontal accuracy are calculated by comparing the position

of the building edges between opposing flight lines.

The scanner scale factor and vertical accuracy is calculated through comparison of LiDAR data against control

points along the runway. Field calibration is performed on all flight lines to refine the IMU misalignment angles. IMU

misalignment angles are calculated from the relative displacement of features within the overlap region of adjacent

(and opposing) flight lines. The raw LiDAR data is reduced using the refined misalignment angles.

Once the data acquisition and GPS processing phases are complete, the LiDAR data was processed

immediately to verify the coverage had no voids. The GPS and IMU data was post processed using differential and

Kalman filter algorithms to derive a best estimate of trajectory. The quality of the solution was verified to be

consistent with the accuracy requirements of the project.

The individual flight lines were inspected to ensure the systematic and residual errors have

been identified and removed. Then, the flight lines were compared to adjacent flight lines for any mismatches to

obtain a homogenous coverage throughout the project area. The point cloud underwent a classification process to

determine bare-earth points and non-ground points utilizing "first and only" as well as "last of many" LiDAR

returns. This process determined bare-earth points (Class 2), noise (Class 7), water (Class 9) ignored ground

(Class 10), unclassified data (Class 1), overlap points (Class 12), and bridges (Class 13). The bare-earth

(Class 2 - Ground) LiDAR points underwent a manual QA/QC step to verify that artifacts have been removed

from the bare-earth surface. The surveyed ground control points are used to perform the accuracy checks and

statistical analysis of the LiDAR dataset.

Breaklines defining lakes, greater than two acres, and double-line streams, wider than

100 feet (30.5 meters), were compiled using digital photogrammetric techniques as part of the hydrographic

flattening process and provided as ESRI Polyline Z and Polygon Z shape files. Breaklines defining water

bodies and streams were compiled for this task order. The breaklines were used to perform the hydrologic

flattening of water bodies, and gradient hydrologic flattening of double line streams. Lakes, reservoirs

and ponds, at a nominal minimum size of two (2) acres or greater, were compiled as closed polygons. The

closed water bodies were collected at a constant elevation. Rivers and streams, at a nominal minimum width

of 100 feet (30.5 meters), were compiled in the direction of flow with both sides of the stream maintaining

an equal gradient elevation. The hydrologic flattening of the LiDAR data was performed for inclusion in the

National Elevation Dataset (NED).

The NOAA Office for Coastal Management (OCM) received the files in las format. The files contained Lidar elevation and intensity measurements.

The data were in Indiana State Plane projection east (1301) in feet and NAVD88 Geoid 09 vertical datum. OCM performed the following processing to the

data to make it available within the Digital Coast:

1. The data were converted from State Plane coordinates to geographic coordinates.

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

3. The high and low error outlier elevations were removed and variable length records (vlr) were removed.

4. The LAS data were sorted by latitude and the headers were updated.

5. Originally classed points as bridges (classification 13) were moved to ASPRS class 17 (bridge deck)