Process_Description:
The LiDAR data was captured using an Aero Commander 500 Shrike and the Cessna 320 Skynight (twin-piston), fixed wing aircraft equipped with a LiDAR system. The LiDAR system includes a differential GPS unit and inertial measurement system to provide superior accuracy.
Acquisition parameters:
1. Scanner - ALTM Gemini LiDAR
2. Flight Height - 1700 meters above mean terrain
3. Swath Width - 32 degrees
4. Sidelap - 50%
5. Nominal Post Spacing - 1.2m
GPS and IMU processing parameters:
1. Processing Programs and version - Applanix POSPac, version 4.4
2. Maximum baseline length - Not greater than 50km.
3. Number of base stations during LiDAR collection - A minimum of 2.
4. Max separation between base stations during LiDAR collection - 0.10m
5. IMU processing monitored for consistency and smoothness - Yes.
Point Cloud Processing:
1. Program and version - Optech's Dashmap 5.20
2. Horizontal Datum - NAD83
3. Horizontal Coordinates - WISCRS Monroe County, in US Survey Feet.
4. Vertical Datum - NAVD88
5. Geoid Model used to reduce satellite derived elevations to orthometric heights - NGS Geoid09.
LiDAR Processing:
1. Processing Programs and versions - TerraSolid TerraScan (version 011.015), TerraModeler (version 011.005 and TerraMatch (version 011.011) and Intergraph MicroStation (version.08.05.02.70).
2. Point Cloud data is imported to TerraScan in a Microstation V8 (V) CAD environment in a PLSS tiling scheme.
3. Analyze the data for overall completeness and consistency. This is to ensure that there are no voids in the data collection.
4. Inspect for calibration errors in the dataset using the TerraMatch software. This is accomplished by sampling the data collected across all flight lines and classify the individual lines to ground. The software will use the ground-classified lines to compute corrections (Heading, Pitch, Roll, and Scale).
5. Orientation corrections (i.e. Calibration corrections) are then applied (if needed) to the entire dataset.
6. Automatic ground classification is performed using algorithms with customized parameters to best fit the project area. Several areas of varying relief and planimetric features were inspected to verify the final ground surface.
7. Quality Assurance and Quality Control (QA/QC) points were captured in 'open terrian' land cover category that were used to test the accuracy of the LiDAR ground surface. TerraScan's Output Control Report (OCR) was used to compare the QA/QC data to the LiDAR data. This routine searches the LiDAR dataset by X and Y coordinate, finds the closest LiDAR point and compares the vertical (Z) values to the known data collected in the field. Based on the QA/QC data, a bias adjustment was determined, and the results were applied to the LiDAR data. A final OCR was performed with a resulting RMSE of 0.226 ft for the project.
8. Once the automatic processing and testing of LiDAR is complete, the generated bare-earth surface data is reviewed to ensure that proper classification was achieved as part of a Quality Control process.
9. Final deliverables are generated and output to a client specified PLSS tiling scheme.