Wayne and Washtenaw Counties 1.0 PPSM LiDAR

TASK NAME: Wayne and Washtenaw Counties 1.0 PPSM LiDAR

LiDAR Data Acquisition and Processing Production Task

USGS CONTRACT: 07CRCN0006

TASK ORDER NUMBER: G09PD00300

CONTRACTOR: Woolpert, Inc.

LiDAR data is a remotely sensed high resolution elevation data collected by an airborne platform. The LiDAR sensor uses a combination of laser range finding, GPS positioning, and inertial measurement technologies.The LiDAR systems collect data point clouds that are used to produce highly detailed Digital Elevation Models (DEMs) of the earth's terrain, man-made structures, and vegetation. This data was collected at a resolution of one point per square meter. The final products include reflective surface, first, last, and at least one intermediate return, a bare earth model, and intensity data in separate files.

The reflective surface data represents the DEM created by the laser energy reflected from the first surface encountered by the laser pulse. Some energy may continue beyond this initial surface, to be reflected by a subsequent surface as represented by the last return data. Intensity information is captured from the reflective surface pulse and indicates the relative energy returned to the sensor, as compared to the energy transmitted. The intensity image is not calibrated or normalized but indicates differences in energy absorption due to the the interaction of the surface materials with laser energy, at the wavelength transmitted by the sensor. The bare earth model is created by identifying the returns that fall on the ground surface and by interpolating a surface between these points. In this manner, buildings and vegetation are removed from the bare earth model. This data set does not include bridges and overpasses in the bare earth model as the delineation point for these structures is not reliably discernible in the LiDAR data.

This task order consisted of LiDAR data acquisition and processing for Wayne and Washtenaw Counties in southeastern Michigan. The task order area of interest encompasses approximately 1324 square miles. The task required the LiDAR data to be collected at a minimum of one (1) point per square meter (1.0 meter GSD). The LiDAR data was collected to meet a vertical accuracy requirement of 18.0 cm (0.59 ft) RMSE, or better, so that when combined with breaklines, the data adequately supports the generation of two (2) foot FEMA compliant contours. The final LiDAR data was delivered as 5,000' x 5,000' tiles, aligned to even 5,000' coordinates. The LAS files are comprised of the full class data.

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Reports for this project are available at:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/4809/supplemental/mi2009_usgs_wayne_washtenaw_m4809_surveyreport.pdf https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/4809/supplemental/mi2009_usgs_wayne_m4809_surveyreport.pdf

A footprint of this data set may be viewed in Google Earth at:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/4809/supplemental/mi2009_usgs_wayne_washtenaw_m4809.kmz

LAS 1.2 format (classes 1,2,8,9,12)

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Any conclusions drawn from the analysis of this information are not the responsibility of Woolpert, USGS, NOAA, the Office for Coastal Management or its partners.

This data can be obtained on-line at the following URL:

https://coast.noaa.gov/dataviewer/#/lidar/search/where:ID=4809

The data set is dynamically generated based on user-specified parameters.;

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Users should be aware that temporal changes may have occurred since this data set was collected and some parts of this data may no longer represent actual surface conditions. Users should not use this data for critical applications without a full awareness of its limitations. These data depict the heights at the time of the survey and are only accurate for that time.

The LiDAR collected for this task order was collected at a vertical accuracy of 18.0 cm (0.59 ft) Root Mean Squared (RMSE), or better, so that when combined with breaklines, it will adequately support the generation of two (2) foot FEMA compliant contours. | Quantitative Value: 18.0 cm (0.59 ft) RMSE | Quantitative Test Explanation: Points measured will produce an error less than 18.0 cm (0.59 ft) RMSE.

Horizontal accuracy is +/- 1.158 meters at the 95% confidence level using RMSE(r) x 1.7308 as defined by the FGDC Geospatial Positional Accuracy Standards, Part 3: NSSDA.; Quantitative Value: 0.669 meters, Test that produced the value: 66.9 cm RMSE

The LiDAR data vertical accuracy RMSE is 8.84 cm.

The data collected under this Task Order meets the National Standard for Spatial Database Accuracy (NSSDA) accuracy standards. The NSSDA standards specify that vertical accuracy be reported at the 95 percent confidence level for data tested by an independent source of higher accuracy. (http://www.fgdc.gov/standards/projects/FGDC-standards-projects/accuracy/part3/index_html).

The Fundamental Vertical Accuracy (FVA) of the TIN: 36.3 cm (1.19 ft) at a 95% confidence level, derived according to NSSDA, i.e., based on RMSE of 18.5 cm in the "open terrain" land cover category. This data set tested to 0.56 ft.

The Supplemental Vertical Accuracy (SVA) of the TIN: 36.3 cm (1.19 ft) at a 95% confidence level, derived according to American Society for Photogrammetry and Remote Sensing (ASPRS) Guidelines, Vertical Accuracy Reporting for LiDAR Data, i.e., based on the 95th percentile error in each of the individual other land cover categories. This criterion is a target value; larger errors in category could be offset by smaller errors in other categories so long as the overall consolidated vertical accuracy (CVA) is satisfied.This data set tested to 0.56 ft. for all categories.

The Consolidated Vertical Accuracy (CVA): 36.3 cm (1.19 ft) at a 95% confidence level, derived according to ASPRS Guidelines, Vertical Accuracy Reporting for LiDAR Data, i.e., based on the 95th percentile error in all land cover categories combined. This data set tested to 0.56 ft. for all categories.; Quantitative Value: 0.0884 meters, Test that produced the value: 8.84 cm RMSEz

The LIDAR data is visually inspected for completeness to ensure that are no gaps between flight lines.

All formatted data are validated using commercial GIS software to ensure proper formatting and loading prior to delivery.