SWRPC has a requirement for lidar covering approximately 278 square miles in Wisconsin collected at a nominal pulse spacing (NPS) of 2 feet.
The project consisted of acquisition, post-processing, and classification of LiDAR data. The classified bare-earth data achieved the following: Kenosha shall be collected at a nominal pulse spacing (NPS) of 2 feet based on Wisconsin State Plane Coordinates, South Zone, related to the North American Datum of 1927. Vertical accuracy was to achieve a RMSE Z of .3ft (95% confidence level of less than .59ft) or better in the "Open Terrain" land cover category.
Accuracy statement is based on the area of moderate to flat terrain. Diminished accuracies are to be expected in areas in dense vegetation. The accuracy of the LiDAR data as tested met the vertical accuracy or better, however, derived products may be less accurate in areas of dense vegetation due to a lesser number of points defining the bare-earth in these areas.
Acquisition parameters: 1. Scanner - Optech ALTM Gemini 2. Flight Height - 1000m above mean terrain 3. Swath Width - 34 degrees 4. Sidelap - 50% for both areas 5. Nominal Post Spacing - 2 ft
GPS and IMU processing parameters: 1. Processing Programs and version - Applanix - POSGPS and POSProc, versions 4.4 2. Maximum baseline length - Not greater than 40km. 3. Number of base stations during LiDAR collection - A minimum of 2. 4. Max separation between base stations during LiDAR collection - 0.09m 5. IMU processing monitored for consistency and smoothness - Yes.
Point Cloud Processing: 1. Program and version - Optech ASDA 2. Horizontal Datum - NAD83(NSRS2007) 3. Horizontal Coordinates - Universal Transverse Mercator, Zone 16, in Meters. 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 009.004), TerraModeler (version 009.001 and TerraMatch (version 009.001) and Intergraph MicroStation (version.08.01.02.15). 2. Point Cloud data is imported to TerraScan in a Microstation V8 (V) CAD environment on a specified 5000 foot by 5000 foot 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. AeroMetric, INC. provided Quality Assurance and Quality Control (QAQC) data for this project. AeroMetric captured QA/QC points in 'open terrain' 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 QAQC data to the LIDAR data. This routine searches the LIDAR dataset by X & Y coordinate, finds the closest LIDAR point and compares the vertical (Z) values to the known data collected in the field. Based on the QAQC 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 0.040m for Area 1 and 0.058m for Area 2. 8. Once the automatic processing and the testing of LiDAR is complete, AeroMetric meticulously reviews the generated bare-earth surface data to insure that proper classification was achieved as part of a Quality Control process. 9. Final deliverables include 362 BE las files generated to a 5,000ft by 5,000ft tiling scheme. The BE files are the Bare Earth (Ground) points from each edited LiDAR file. All 362 BE las files are manually edited to remove non ground points and stored as a 1.2 las file. Deliverables can now be produced.