2005 Oahu/Maui Lidar Mapping Project

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EarthData Aviation was contracted by EarthData International to collect ALS-40 Lidar data over the west coast

of Maui, Hawaii. The project site was flown on March 16th and 24th of 2005, using aircraft N806CP. Lidar data was captured using

an ALS-40 Lidar system, including an inertial measuring unit (IMU) and a dual frequency GPS receiver. Lidar was obtained at an

altitude of 762 meters (2,500 feet) above mean terrain, at an average airspeed of 130 knots. Sensor pulse rate was set at 20,000 Hz

with a field of view of 25 degrees and a rate of 17 Hz. Average swath width of the collected raw lines is 337 meters. Lidar data

was recorded in conjunction with airborne GPS and IMU; the stationary GPS receiver was positioned over a control point located

at the airport. Recorded digital data was shipped via external hard drive to the production facility for processing. During

airborne data collection, an additional GPS receiver was in constant operation over a published National Geodetic Survey (NGS)

control point at Kahului Airport. The control point with designation OGG ARP 2 and PID AA3608, is "A" Order horizontal with

Third Order Class II ellipsoid height. During the data acquisition, the receivers collected phase data at an epoch rate of 1 Hz.

All GPS phase data was post processed with continuous kinematic survey techniques using "On the Fly" (OTF) integer ambiguity

resolution. The GPS data was processed with forward and reverse processing algorithms. An adjustment was made to the ellipsoid

height of the published point by Terrasurv to reflect Local Tidal Elevation. The results from each process, using the data

collected at the airport, were combined to yield a single fixed integer phase differential solution of the aircraft trajectory.

| Source Geospatial Form: Model | Type of Source Media: Firewire Drive

EarthData Aviation was contracted by EarthData International to collect ALS-40 Lidar data over the coastal

area of Oahu, Hawaii. The project site was flown on February 20 and March 2, 3, 6, 12, 13 using its aircraft with tail number

N806CP. Lidar data was captured using an ALS-40 Lidar system, including an inertial measuring unit (IMU) and a dual frequency

GPS receiver. Lidar was obtained at an altitude of 762meters (2,500 feet) above mean terrain, at an average airspeed of 130

knots. Sensor pulse rate was set at 20,000 Hz with a field of view of 25 degrees and a scan rate of 17 Hz. Average swath width

of the collected raw lines is 338 meters. Point spacing was 2 meters. Lidar data was recorded in conjunction with airborne GPS

and IMU; the stationary GPS receiver was positioned over a control point located at the airport. Recorded digital data was

shipped via external hard drive to the production facility for processing. During airborne data collection, an additional GPS

receiver was in constant operation over a published National Geodetic Survey (NGS) control point at Honolulu Airport. The

coordinate value for temporary control point "PHNL" was determined by a network adjustment to CORS stations EHN1 and HNLC,

both of which were tied to the project control network. During the data acquisition, the receivers collected phase data at an

epoch rate of 1 Hz. All GPS phase data was post processed with continuous kinematic survey techniques using "On the Fly" (OTF)

integer ambiguity resolution. The GPS data was processed with forward and reverse processing algorithms. An adjustment was made

to the ellipsoid height of the published point by Terrasurv to reflect Local Tidal Elevation. The results from each process,

using the data collected at the airport, were combined to yield a single fixed integer phase differential solution of the aircraft

trajectory.

| Source Geospatial Form: Model | Type of Source Media: Firewire Drive

Kevin Chappell, of Terrasurv and under contract to EarthData International established 6 ground control points.

The points were surveyed using GPS for both vertical and horizontal coordinate values. The horizontal datum used was the North

American Datum of 1983 (Pacific Plate Fixed Realization, epoch 2002.0). The vertical datum used was a Local Tidal Datum.

| Source Geospatial Form: Diagram | Type of Source Media: Electronic mail system

Kevin Chappell, of Terrasurv and under contract to EarthData International established 30 ground control

points along the coastline of the island of Oahu and within a blocked area around Honolulu where the 2005 flight was flown.

The points were surveyed using GPS for both vertical and horizontal coordinate values. The horizontal datum used was the North

American Datum of 1983(Pacific Plate Fixed Realization, epoch 2002.0). The vertical datum used was a Local Tidal Datum.

| Source Geospatial Form: Diagram | Type of Source Media: Electronic mail system

EarthData has developed a unique method for processing lidar data to identify and remove elevation points

falling on vegetation, buildings, and other aboveground structures. The algorithms for filtering data were utilized within

EarthData's proprietary software and commercial software written by TerraSolid. This software suite of tools provides efficient

processing for small to large-scale, projects and has been incorporated into ISO 9001 compliant production work flows. The

following is a step-by-step breakdown of the process.

1. Using the lidar data set provided by EarthData, the technician performs calibrations on the data set.

2. Using the lidar data set provided by EarthData, the technician performed a visual inspection of the data to verify that the

flight lines overlap correctly. The technician also verified that there were no voids, and that the data covered the project

limits. The technician then selected a series of areas from the data set and inspected them where adjacent flight lines

overlapped. These overlapping areas were merged and a process which utilizes 3-D Analyst and EarthData's proprietary software

was run to detect and color code the differences in elevation values and profiles. The technician reviewed these plots and

located the areas that contained systematic errors or distortions that were introduced by the lidar sensor.

3. Systematic distortions highlighted in step 2 were removed and the data was re-inspected. Corrections and adjustments can

involve the application of angular deflection or compensation for curvature of the ground surface that can be introduced by

crossing from one type of land cover to another.

4. The lidar data for each flight line was trimmed in batch for the removal of the overlap areas between flight lines. The

data was checked against a control network to ensure that vertical requirements were maintained. Conversion to the client-specified

datum and projections were then completed. The lidar flight line data sets were then segmented into adjoining tiles for batch

processing and data management.

5. The initial batch-processing run removed 95% of points falling on vegetation. The algorithm also removed the points that

fell on the edge of hard features such as structures, elevated roadways and bridges.

6. The operator interactively processed the data using lidar editing tools. During this final phase the operator generated a

TIN based on a desired thematic layer to evaluate the automated classification performed in step 5. This allowed the operator

to quickly re-classify points from one layer to another and recreate the TIN surface to see the effects of edits.

Geo-referenced images were toggled on or off to aid the operator in identifying problem areas. The data was also examined with

an automated profiling tool to aid the operator in the reclassification.

7. The final DEM was written to an ESRI grid format (.flt).

8. The point cloud data were also delivered in LAS format.

The NOAA Office for Coastal Management (OCM) received LAS files containing the point cloud elevation data from

Earth Data, Inc. OCM performed the following processing on the data to make it available within the Lidar Data Retrieval

Tool (LDART):

1. Variable length header records were added to the LAS files to identify projection, datum and sort order.

2. The LAS files were sorted by latitude.

For data management purposes, the Office for Coastal Management converted the data from NAVD88 elevations to

ellipsoid elevations using Geoid 99.